Innovative Biological Technologies forLesser Developed Countries

July 1985

NTIS order #PB86-121738

Recommended Citation:Innovative Biological Technologies for Lesser Developed Countries— Workshop Pro-ceedings (Washington, DC: U.S. Congress, Office of Technology Assessment, OTA-13P-F-29, July 1985).

Library of Congress Catalog Card Number 85-600550

For sale by the Superintendent of DocumentsU.S. Government Printing Office, Washington, DC 20402

Preface

Oversight of the Agency for International Development (AID) is the responsi-bility of the House Committee on Foreign Affairs. In 1980, under Chairman Cle-ment Zablocki, the Committee requested the Food and Renewable ResourcesProgram of the congressional Office of Technology Assessment (OTA) to reviewinnovative biological technologies that AID could use to help lesser developed coun-tries (LDCs) enhance the productivity of their soils, reduce their need for costlychemical fertilizers, and increase food supplies,

In response to the committee’s request, OTA hosted a workshop that broughttogether some 40 leading scientists, AID representatives, and congressional andexecutive branch staff for 2 days of presentations and discussions on November24 and 25, 1980 (see attendees list). On the first day of the workshop each scientistpresented a paper about innovative biological technologies and responded to ques-tions. The second day was devoted to discussing AID and its role in using, promot-ing, and developing innovative biological technologies, Chapters I and II of thisreport summarize those two days of discussion. Chapters III through XII containthe scientific papers that were presented at the workshop.

These Workshop Proceedings were first released by the Committee on ForeignAffairs in 1981. Continued requests for copies of the proceedings spurred thisreprinting. Although the papers have been edited slightly for style, they have notbeen updated, OTA wishes to thank the authors of the papers, the other workshopparticipants, reviewers, and the many people worldwide who have requested copies.

Workshop Participants

James DukeUSDA/ARSGermplasm Resources LaboratoryBuilding 001, Room 131BARC—WestBeltsville, MD 20705

Peter FelkerCeasar Kleberg WildlifeCollege of AgricultureTexas A&I UniversityKingsville, TX 78363

Stephen R. GliessmanAgroecology ProgramBoard of EnvironmentalUniversity of CaliforniaSanta Cruz, CA 95064

Jake HallidayBattelle KetteringResearch Laboratory

Research Institute

Studies

150 East South College St.Yellow Springs, OH 45387

William LiebhardtRodale Research CenterRD1 BOX 323Kutztown, PA 19530

Thomas A. LumpkinDepartment of Agronomy and Soil ScienceWashington State UniversityPullman, WA 99164-6420

Cy McKellDirector of ResearchN.P.I.417 Wakara WayUniversity Research ParkSalt Lake City, UT 84108

John MengeDepartment of Plant PathologyUniversity of CaliforniaRiverside, CA 92521

Frederick MumptonDepartment of the Earth SciencesState University of New YorkBrockport, NY 10003

Donald PlucknettCGIARWorld Bank1818 H St., N.W.Room K1045Washington, DC 20433

Noel VietmeyerNational Academy of SciencesNational Research CouncilJH 213BOSTID2101 Constitution Ave., N.W.Washington, DC 20418

OTA Workshop Staff on Innovative Biological Technologiesfor Lesser Developed Countries

Joyce C. Lashofl1and Roger Herdman,2 Assistant DirectorOTA Health and Life Sciences Division

Ogechee Koffler, Division Assistant

Walter s E. Parham, Food and Renewable Resources Program Manager

Bruce Ross, Project Director

Contractors

Chris Elfring

Hugh Bollinger

Editor

Chris Elfring

Administrative Staff

Phyllis Balan 3 and Patricia Durana,4 Administrative Assistant

Elizabeth Galloway, Secretary

Gillian Raney, Secretary

Nellie Hammond, Secretary

Carolyn Swarm, Secretary

1Until December 1981.2Current Assistant Director,3Until September 19844From October 1984.

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Contents

Chapter PageI. The Potential of Innovative Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

11. The Role of the Agency for International Development . . . . . . . . . . . . . . . . 2 3

111, Underexploited Plant and Animal Resources for Developing CountryAgriculture (Noel Vietmeyer) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

IV. Native Plants: An Innovative Biological Technology(Cyrus M. McKell) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

V. Multiple Cropping Systems: A Basis for Developing an AlternativeAgriculture (Stephen R. Gliessman) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

VI. Development of Low Water and Low Nitrogen Requiring PlantEcosystems for Arid Developing Countries (Peter Feller) . . . . . . . . . . . . . . . 8 7

VII. Azolla, A Low Cost Aquatic Green Manure for Agricultural Crops

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(Thomas A. Lumpkin and Donald L. Plucknett) . . . . . . . . . . . . . . . :. . . . . . . . 107

Using Zeolites in Agriculture (Frederick A. Mumpton) . . . . . . . . . . . . . . . . . 127

Agrotechnologies Based on Symbiotic Systems That Fix Nitrogen(Jake Halliday) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

X. Mycorrhiza Agriculture Technologies (John A. Mange) . . . . . . . . . . . . . . . . . 185

XI. A Low Fertilizer Use Approach to Increasing Tropical Food Production(William C. Liebhardt) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

XII. The Gene Revolution (James A. Duke) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

Chapter I

The Potential of

Contents

P a g e

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..., . . . . . . . . . . . . . . . . , . . . . . . . . .What Do Innovative Technologies Offer? .,, ,..,... . . . . . . . . . . . . . . . . . . . . . . . . . . .The Workshop’s Conclusions . . . . . . . . . . . . . . . . . , , . . . . . . ., , . . . . . . . . . . , , ,.., . . .Innovative Biological Technologies: Highligh

Underexploited Plant Resources . . . . . . .Multiple Cropping . . . . . . . . . . . . . . . . . . . .

s of the workshop, , ., . . . . . . . . . . , , .. . . . . . . . . . . ,.,,.. . . . . . . ,.,,., ,.,...,., . . . . . . . . . . . . ,..,,. . . . . . . . . . .

Agroforestry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., . . . . . . . . . . . . . . . . . . . . . . . . . . ,Azolla/Algae Symbiosis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Underexploited Animal Species . . . . . . . . . . . . . . . . . . . . ..., , . . . . . . . . . . . . . . . .Zeolites . . . . . . . . . . .Biological Nitrogen FMycorrhizal Fungi..

. . . . . . . . . . . . . . . . . . . . . . . . . . . .,,,,,. . . . . . . . ,..,.,, ,.xation . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Chapter I

The Potential ofInnovative Technologies

INTRODUCTION

Fertile soil is the key to productive agricul-ture, whether for an Illinois corn farmer or asubsistence farmer in Ghana, Haiti, India, orother less developed country (LDC). The farm-ers know this; they know their soil must havegood tilth, hold water, and be rich with the nec-essary nutrients and minerals. They learn theseprinciples through education or, more likely,through tradition and experience. But for mostLDC farmers, the old ways of maintaining soilquality may no longer be adequate. Populationpressures and rising expectations force themto demand more from the land, to shorten thetraditional fallow periods, and to open mar-ginal lands that past generations could avoidusing. The farmers may turn to modern agri-cultural methods—e.g., commercial fertilizers—only to find that the rising costs of these in-puts prohibit even this option, This predica-ment is common throughout LDCs.

Most LDCs, with their growing populations,are concentrated in a belt roughly 30 degreesnorth and south of the Equator. These tropi-cal and subtropical lands contain diverse eco-systems: mountains, rainforests, semiarid re-gions, and deserts, and house some 45 percentof the Earth’s people. The concentration ofLDCs in the Tropics is not a coincidence butstems in large part from inherent physicallimitations caused by climatic and soil con-straints. As the populations of these nationshave grown, many LDCs have come to face amyriad of severe resource problems: degradedsoil fertility, deforestation, soil erosion, waterpollution, and land-use conflicts, Concomitantsocial problems—including malnutrition, pov-erty, and political instability—are common aswell.

The humid tropical regions have some of theEarth’s most productive ecosystems—lushforests that are the result of eons of long grow-ing seasons and abundant rainfall. But thisapparent fertility is often superficial. Tropicalforests have been called “deserts covered bytrees. ” In fact, natural soil fertility in the wettropical latitudes is extremely low becausemost of the minerals have been leached fromthe soil by ages of rain and weathering, Thenutrients are trapped in the vegetation itself;as the greenery dies and decays on the forestfloor, the nutrients are released, then quicklyabsorbed into new growth.

Arid and semiarid regions face differentproblems. Lack of water limits the type andamount of crops that can be grown. Wind ero-sion, salinization, and temperature extremesall work to limit the land’s productivity.

Agriculture in tropical latitudes must con-tend with these and other physical dictates. Itmust work within increasingly severe eco-nomic constraints, too, as the costs of energy,water, equipment, and various other agricul-tural inputs, from seed to fertilizer, continueto rise,

Conventional agricultural methods, many ofwhich were developed for use in temperateareas, are not wholly suitable for tropical con-ditions, It is not that conventional agriculturecannot work in the Tropics; it can, in the shortrun. But without continuous fertilizer inputs,poor tropical soils cannot sustain temperatefarming methods, Also, in arid and semiaridregions temperate farming technologies requirecostly irrigation systems. Thus, with the in-creasing expense of irrigation development

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and fertilizers derived from natural gas, itseems inevitable that LDC farmers will look fornew ways to sustain soil fertility and to ensurecontinued agricultural productivity.

The Agency for International Development(AID) is one mechanism by which the UnitedStates can help LDCs meet development andresource challenges. AID has been commendedfor many of its programs, but it also has been

cited for its reluctance to change and for itslack of innovative vision at a time when in-novation seems most necessary, This workshopreviewed a number of innovative biologicaltechnologies that might help LDCs enhancetheir agricultural productivity and it takes aspecial look at the role AID plays, and couldplay, in developing these technologies.

WHAT DO INNOVATIVE TECHNOL0GIES OFFER?

The innovative biological technologies cho-sen for discussion in the workshop representonly a sample of the diverse and adaptable ap-proaches being studied by scientists here andabroad. The workshop examined the following:

c promoting underexploited plant species,especially native species already adaptedto local climates and conditions. Natureis a storehouse of genetic possibilities in-cluding plants with potential as food, fod-der, oil seeds, and export goods. Nativeplants can be integrated into cropping sys-tems, reducing the need for fertilizer andwater and enhancing resistance to pestsand disease, There is also promise in plantbreeding efforts and tissue culture, wherenative stocks are used to adapt crops toless than ideal environments, This reducesthe need to alter the environment with fer-tilizer, irrigation, and other expensiveinputs,

● Developing multiple-cropping and inter-cropping systems suitable for specific trop-ical environments as a way to maximizeland productivity. Multiple cropping is in-tensive agriculture—growing two or morecrops that share space and resources andcan produce more per unit of land thanmonoculture. Proper design of the crop-ping pattern—e.g., using legumes—ensuresand enhances soil quality while providingfarmers with a range of products.

● Designing integrated agricultural systemsthat take advantage of the special benefitsprovided by leguminous trees. Various spe-

cies of nitrogen-fixing trees (e. g., Prosopisand Acacia] could be used to revegetatedeforested landscapes while providingfood, fodder, cash crops, fuelwood, and in-creased soil fertility. Unlike legumes usedin temperate agriculture (e. g., alfalfa),many of these tree species can fix nitro-gen under arid conditions.

● Cultivating “green” fertilizer for rice pro-duction. Azolla, a small aquatic fern nativeto Asia, Africa, and the Americas, showsgreat promise as a green manure, The fernprovides nutrients and a protective leafcavity for a strain of blue-green algae,which in turn converts atmospheric nitro-gen into a usable form. The nitrogen-richazolla is grown in rice paddies, eitherbefore or along with the rice crop, It alsocan be harvested and transported to up-land fields,

● Using underexploited animal species tomeet local needs for high protein food aswell as to provide local populations withinnovative cash crops, For instance, inPeru, guinea pigs are being produced asan unconventional, but tasty and prolific,protein source for local diets. And inPapua, New Guinea, villagers are supple-menting farm income by tending an addi-tional garden crop—exotic butterflies forexport.

● Exploring the use of natural mineral soilamendments, e.g., zeolite minerals, thatimprove soil properties and extend fer-tilizer efficiency. Because of their struc-ture, zeolites have unique properties. They

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are used today primarily as molecularsieves in industrial processes, but theyshow promise in agriculture. They seemable to help maintain nitrogen availabilityin soils and help plants resist water stress.More immediate benefits may show in ani-mal agriculture, where zeolites can serveas feed additives and as decontaminantsfor feedlot wastes, and in fish farming. ●

Zeolite deposits are thought to be wide-spread in many LDCs.Reducing the need for commercial nitro-gen fertilizer by inoculating suitable cropswith beneficial soil bacteria—rhizobia—that biologically take nitrogen from the airand convert it to a usable form for theplant. Legume rotations, of course, were

fundamental to agriculture before the de-velopment of commercial fertilizers. Theserotations relied on the natural abundanceof rhizobia, but improved strains mightgarner even better results. Legume in-oculants are used commercially in U.S.agriculture and suitable strains are beingdeveloped for LDC environments.Increasing a plant’s capacity to absorbnutrients by encouraging the growth ofbeneficial micro-organisms–mycorrhizalfungi—that live in association with someplants. The mycorrhizae significantly in-crease the root’s surface area—the part ofthe plant that assimilates nutrients fromthe soil.

THE WORKSHOP’S CONCLUSIONS

Workshop participants shared a general feel-ing that a range of promising, innovative tech-nologies exists in various stages of develop-ment that could help LDCs sustain soil fertilitywith reduced fertilizer inputs. However, thesetechnologies are underused and many impor-tant ones are being ignored by the developmentcommunity. Many of the innovative approachesdiscussed are “technologies” in the broadestsense; they are new management systems, notnew pieces of hardware.

Research on such innovative techniques gen-erally is underfunded, perhaps because of tech-nological complexity, human reluctance tostray too far from the norm, or well-intentionedskepticism about radically new or unprovenapproaches to agriculture. Thus, it is all themore difficult to document their worth. Mostof the technologies, while promising, needpilot-scale testing in appropriate environmentsto determine potential problems or necessaryalterations before they can be promoted on awide scale. Also, workshop participants thought

that much of the development of innovativetechnologies is occurring outside of, and per-haps in spite of, the national and internationalinstitutions normally considered responsiblefor maintaining natural resources and for deal-ing with problems of land quality and produc-tivity.

A particularly interesting facet of these newtechnologies is that many of them could bene-fit not only LDC agriculture but also U.S.agriculture by providing opportunities for eco-nomic diversification, reducing soil degrada-tion, and bolstering production while lower-ing capital costs.

No new technology, of course, can be a pan-acea. The importance of innovation lies in thefact that each new approach increases thenumber of options available to deal with prob-lems, More choices thus provide increasedadaptability to changing social, economic, andphysical conditions.

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INNOVATIVE BI0LOGICAL TECHNOLOGIES:HIGHLIGHTS OF THE WORKSHOP

This planet is believed to house some 80,000species of edible plants. Man, at one time oranother, has used 3,000 of those for food. Butonly about 150 plants have been cultivated ona large scale, and less than 20 crops currentlyprovide almost 90 percent of the world’s food.

It is clear that mankind could exploit morefully the range of botanical diversity found onEarth. In developing countries, various inno-vative uses of plant resources show great prom-ise and could help enhance land productivityand increase food supplies. First, it is possibleto expand the range of crops grown by usingunderexploited plant species, especially nativespecies already adapted to local climates andconditions, Second, special attention could bedevoted to the potentials of leguminous spe-cies, including leguminous trees, that are ca-pable of converting atmospheric nitrogen intoa usable form and thus enhancing soil fertilitywhile reducing reliance on expensive com-mercial fertilizers. Further, innovative andconventional crops could be used together inmultiple cropping or intercropping systems de-signed for specific tropical environments tomaximize efficient resource use and land pro-ductivity.

The first day of the two-day OTA workshopwas devoted to discussions of particular inno-vative biological technologies—their potentialadvantages for LDC users and problems limit-ing their use or development. Here are high-lights of those discussions.

Underexploited Plant Resources

Every culture, of course, has indigenous spe-cies that have been used traditionally for food,fuel, livestock feed, construction, fiber, medi-cine, and other purposes either gathered fromthe wild or cultivated in various small farm-ing systems. But until recently, these traditionalcrops in LDCs had been lost in the shadowsof the Green Revolution and westernized farm-ing techniques.

Now, however, there is renewed optimismabout the agricultural potential of many ofthese plant resources. Native plants can beinnovative sources of a wide range of goods—food for people and livestock, fuelwood forcooking and warmth, materials for homes andclothing, even oil seeds and other exports. Thebenefits provided are compounded becausenative plants can require fewer total inputs offertilizer, herbicides, insecticides, energy, andin some cases water. This is because native spe-cies are adapted to local environmental con-ditions–soil type and quality, climate andterrain. Indigenous species often are more re-silient to stress, as well; they have evolveddefenses for local disease and pest organismsand evolved to be efficient users of availableresources, whether water, soil nitrogen, orother necessary nutrients. The native plantconcept is a reversal of the old philosophy ofusing inputs to change the soil to suit the crop.Here the crop is chosen to suit the soil. Ex-amples of innovative plants include:

Winged bean (Psophocarpus tetragonolobus):Generally identified as a “poor people’s crop”in developing countries, the winged bean’s nu-tritional potential has been vastly underrated.Actually, this plant, sometimes called a “super-market on a stalk, ” has at least six edible parts.The leaves are used like spinach as a vegetableor salad; the flowers are edible, tasting some-what like mushrooms; the pods, similar togreen beans, are nutritious and palatable; theseeds are similar to soybeans and are com-posed of 17 percent oil and 42 percent protein;the tendrils are also edible and taste like aspar-agus; and the below-ground tubers contain fourtimes the protein of potatoes.

Amaranth (Amaranths hypochondriacs):Once the mainstay of certain ancient SouthAmerican cultures, amaranth is a fast-growing,cereal-like crop that produces high-proteingrains in large, sorghum-like seed heads. Thegrain is also exceptionally high in lysine—oneof the critical amino acids usually deficient in

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plant protein. Amaranth grain is usually parchedand milled to be used for pancakes, cooked forgruel, or blended with other flours. Its leavescan be eaten as a spinach substitute.

Leucaena (Leucaena Zeucocephala): Of alltropical legumes, leucaena probably offers thewidest assortment of uses. It is a fast-growingtree that produces good, dense firewood; itfixes nitrogen in the soil; and its leaves makenutritious cattle forage. This leguminous treeis especially valuable in reforestation efforts.

Any change in the use of fertilizer, pesticides,irrigation, or machinery would depend entirelyon the nature of the native plant chosen forcultivation—whether the particular plant couldbe used on an intensive or extensive basis, thedegree to which the plant is susceptible topests, and many other variables.

Water needs, too, would vary with the spe-cific species chosen for cultivation. Speciesadapted to tropical soils and moist climatesshould not require irrigation provided that ade-quate rainfall occurs during the critical stagesof plant development. In regions of less thanoptimal precipitation, farmers can choosenative plants with low water requirementssuch as jojoba, atriplex, guayule, buffalo gourd,guar, cassia, and acacia species. It is also pos-sible to enhance the effectiveness of water usethrough management (alternate fallow periods,spaced planting, etc.), water harvesting, anddrip irrigation. Where land is not the limitingfactor, enhanced water harvesting is showinghigh potential for fostering plant productionunder desert conditions, The most suitableplants for these technologies are deep-rootedtree crops, drought adapted species, and bio-mass plantings.

Some native species also offer hope for in-tensive agriculture as certain plants could bedeveloped for large-scale operations. If a low-value crop can be replaced with a high-valuenew crop, irrigation may even be justified.Close plantings, tillage, pest control, and fer-tilization may then be needed to optimize pro-duction and under certain circumstancesmight be economically viable. Grain amaranth,winged bean, and guar are possible species for

intensive development, but many others maybe considered.

Equipment and labor needs also vary de-pending on the specific native plant in ques-tion. Some species (e.g., guar or guayule) areamenable to mechanical harvesting. Manyothers, however, require manual labor, whichcould be an advantage where excessive un-employment exists.

To develop the potential of native plant re-sources, more effort needs to be devoted toidentifying valuable species and adapting themto modern needs. Once identified, researchersneed to look for opportunities to expand theplant’s use into similar environments else-where in the world, Perhaps a better under-standing of the plant diversity available world-wide will lead to more innovation and also anacceptance that folkways are often valid andcould be incorporated into a productive com-promise between old and new customs.

Multiple Cropping

Multiple cropping is intensive agriculturewhere two or more crops share space and re-sources, enhancing both land-use efficiencyand long-term productivity. It is not a new tech-nology but rather is at its roots an ancient tech-nique that mimics the diversity of natural eco-systems.

Today’s multiple cropping systems varygreatly depending on the character of the sitebeing farmed. In general, multiple croppingsystems are managed so that total crop produc-tion from a unit of land is achieved by grow-ing single crops in close sequence, growingseveral crops simultaneously, or combiningsingle and mixed crops in some sequence. Both“sequential cropping, ” which is growing twoor more crops in sequence on the same land,and “intercropping,” which refers to variousways of growing two or more crops simulta-neously on the land, are included in thebroader term “multiple cropping.”

Generally, productivity on multiple croppedland can be more stable and constant in thelong run than in monoculture. Although each

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crop in the mixture may yield slightly less thanin monoculture, combined production per unitarea can be greater with multiple croppedfields. The overall increased yields result be-cause the component crops differ enough intheir growth requirements so that overlappingdemands—whether for sunlight, water, ornutrients—are minimal. Multiple cropping, ineffect, broadens the land’s productive capac-ity by more fully exploiting the dimensions oftime and space.

It is important to point out that not all cropmixtures will produce better yields when multi-ple cropped. Certain combinations make bet-ter overall use of available resources and willbe more successful; these crops are considered“complementary.” One of the main ways toachieve such complementarily is by varying thecrop components temporally—i.e., using se-quential planting to achieve a multiple crop-ping system that avoids antagonistic interac-tions between the components. Such systemsrequire special management—timely harvest-ing, the use of proper varieties, alteration ofstandard planting distances, special selectionof herbicides so as not to create antagonismsor residual effects.

Another way of complementing crop com-ponents is through intercropping based onrelay planting. Direct competition is avoidedby planting a second crop after the first onehas completed the major part of its develop-ment, but before harvest. Research on relaycropping in Mexico and Latin America showsdefinite yield advantages, especially for cornand beans. The success of relay intercroppingdepends on the correct combinations of tim-ing and other variables so as to avoid shading,nutrient competition, or inhibition broughtabout by toxicity produced by the decomposi-tion of previous crop residues. Research inthese areas is inadequate.

Finally, farmers can get maximum comple-mentarily in systems where two or more com-patible crops are grown simultaneously, eitherin rows, strips, or mixed fields. For example,traditional corn, bean, and squash systemsgrown in Mexico show how three species can

benefit from multiple cropping. All three cropsare planted simultaneously, but mature at dif-ferent rates. The beans, which begin to maturefirst, followed by the corn, use the young cornstalks for support. The squash matures last. Asthe corn matures, it grows to occupy the up-per canopy, The beans occupy the middlespace and the squash covers the ground. Re-search shows that the system achieves goodweed and insect control. And while the beansand squash suffer a distinct yield reduction,corn yields are significantly higher than incomparable monoculture. It is still uncertainwhether the higher yields are the result of moreefficient resource use or if some mutually ben-eficial interaction is occurring among the cropcomponents.

Agroforestry

Agroforestry is a multiple cropping manage-ment technology that combines tree crops withfood crops, animal agriculture, or both. Likeother multiple cropping systems, its goal is tooptimize land productivity while maintaininglong-term yields. In the past, small-scale tradi-tional agriculture often included trees as partof the farm design, but interest in agroforestry’splace in modern agriculture is just beginning.Agroforestry systems can be used to bring mar-ginal lands into production—lands with steepslopes, poor soils, or widely fluctuating rain-fall. But tree-crop combinations can also beused on prime agricultural or grazing land tofurther increase productivity. The main limita-tions to widespread use of agroforestry prac-tices is lack of knowledge and expertise, andunwillingness in the agricultural establishmentto accept the idea of long-term, diversifiedyields.

The key to multiple cropping’s benefits is theintensity of the cropping pattern—drawing asmuch as possible from the land resource. De-spite the intense demands, such systems neednot abuse the land; through proper design andoperation, multiple cropping management cansustain and actually enhance soil fertility. De-pending on the multiple cropping system used,advantages can include:

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more efficient use of vertical space andtime, imitating natural ecological patternsand permitting more efficient capture ofsolar energy and nutrients;more biomass (organic matter) available toreturn to the soil;more efficient circulation of nutrients, in-cluding “pumping” them from deeper soilprofiles when deep-rooted species areused;possible reduced wind erosion because ofsurface protection;promise for marginal areas because multi-ple cropping can take better advantageof variable soil types, topography, andsteeper slopes;less susceptible to climatic variation[especially precipitation, wind, and tem-perature);reduced evaporation from soil surface;increased microbial activity in the soil;more efficient fertilizer use through themore diverse and deeper root structure inthe system;improved soil structure, less 1ikelihood toform “hardpan, ” and better aeration andinfiltration;reduced fertilizer needs because legumecomponents fix atmospheric nitrogen forthemselves and associated nonlegumes;heavier mulch cover aids in weed control;better opportunities for biological controlof insects and diseases because of compo-nent plant diversity; andpotential benefits from mutualisms andbeneficial interactions between organismsin crop mixture systems.

But as mentioned, not all crop combinationslend themselves to successful multiple crop-ping and not all forms of multiple cropping arenecessarily good for the land. Sequential crop-ping, for instance, of two or three crops canactually mine the land of nutrients and min-erals if little thought is given to legume rota-tions, green manures, animal manures, or otherfertility-building activities. And in light of thebiological and physical aspects of the agroeco-system, other disadvantages in multiple crop-ping might include:

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competition for light, soil nutrients, orwater;possibility of allelopathic influences be-tween different crop plants caused byplant-produced toxins;potential to harm one crop componentwhen harvesting other components;difficulty building a fallow period intomultiple cropping systems, especiallywhen long-lived tree species are included;difficulties in mechanizing various oper-ations (tillage, planting, harvest, etc.);increases in evapotranspiration caused bygreater root volume and larger leaf surfaceareas;possible overextraction of nutrients, fol-lowed by their subsequent loss from theagroecosystem if they are exported as agri-cultural or forest products;damage to shorter plants from leaf ,branch, fruit or water-drop from tallerplants;higher relative humidity in the air that canfavor disease outbreak, especially of fungi;andpossible proliferation of harmful animals(especially rodents and insects) in certaintypes of systems.

Even though it seems that the biological andphysical advantages of multiple cropping out-weigh the disadvantages, there also is a rangeof social and economic factors that would in-fluence the acceptance and use of multiplecropping technologies in various cultures, Interms of social stability, multiple cropping isadvantageous because it leads to a diverse agri-cultural system. Such a system is less suscep-tible to climatic variation, environmentalstress, and pest outbreaks. It is also less vul-nerable to swings in crop prices and markets.Multiple cropping also demands more constantuse of local labor and provides a more constantoutput of harvested goods over the course ofthe year. And because such systems are highlyadaptable, they can be melded into many dif-ferent types of culture without undue stress onexisting local customs. Multiple cropping alsoprovides farmers with a large variety of usefulproducts, depending on the type and complex-

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ity of their systems. And, of course, multiplecropping systems can reduce the need for fer-tilizers and other energy imports, thus givingLDC farmers improved economic stability andself-sufficiency.

Reported lower yields, complexity of activi-ties and management, higher labor demands,and difficulty mechanizing operations are allfactors that discourage modern farmers frommultiple cropping. Conventional agriculture islooking for short-term profits rather than atmaintaining constant income over the longterm, although it appears that the economicsof farming may be changing to favor such inno-vative systems, especially in the LDCs.

Although there exists the tangible disadvan-tage of potentially lower yields, most of the dis-advantages involved in multiple cropping arederived from lack of experience and knowledgeabout the workings of complicated agroeco-systems,

Azolla/Algae Symbiosis

Rice—one of the most important staple cropsin the world—demands rich, fertile soil. Buttraditional legume crops do not make goodgreen manures for rice farmers; they are reluc-tant to devote part of the valuable growingseason to a relatively slow-growing legumecrop. Furthermore, most legume crops cannotgrow or fix nitrogen in flooded or waterloggedsoils. But these disadvantages can be avoided.Through the use of azolla, a small aquatic fernnative to Asia, Africa, and the Americas, ricefarmers can produce a fast-growing greenmanure that thrives in paddy-like conditions.

Azolla is a genus of small ferns that live nat-urally in lakes, swamps, streams, and otherbodies of freshwater. Its tremendous agricul-tural potential lies in the fact that azolla livesin a symbiotic relationship with a nitrogen-fixing blue-green algae, Anabaena. The delicateazolla fern provides nutrients and a protectiveleaf cavity for the Anabaena. In turn, the algaeproduce enough nitrogen to meet the needs ofboth plants, plus some extra. Under the rightconditions, the fern/algae combination can ac-

tually double in weight every 3 to 5 days andfix nitrogen at a higher rate than most legumeRhizobium symbionts. In 25 to 35 days, azollacan fix enough nitrogen for a 4 to 6 ton/ha ricecrop during the rainy season or a 5 to 8 ton/hacrop under irrigation during the dry season.The nitrogen fixed by the fern/algae combina-tion becomes available to the rice after theazolla mat is incorporated into the soil and itsnitrogen is gradually released as the plantsdecay.

Azolla’s value as a green manure for floodedcrops has been known for centuries by the peo-ple of the People’s Republic of China and Viet-nam. But its use was relatively limited; fewfamilies knew the intricate techniques neededto overwinter and oversummer the sensitivefern successfully, and these families controlledthe distribution of starter-stocks in the spring.After the revolutions in China and Vietnam,the new governments eventually recognizedthe value of azolla and began promoting its use,but their efforts were minimal and progresswas slow, It is only recently that worldwide at-tention has focused on the plant and seriousefforts have been made to search for hardiervarieties for widespread use.

Azolla’s ability to enhance soil fertility oc-curs both because it is an input of nitrogen andof organic matter. Nitrogen, of course, is a nec-essary plant nutrient. Humus, the rich organicmaterial formed through plant decomposition,increases the water-holding capacity of the soiland promotes better aeration and drainage.Organic matter also can bind soil particles to-gether, thereby improving the soil structure.

Azolla also can be important in the cyclingof nutrients. While it is growing, the plant notonly fixes nitrogen but absorbs nutrients outof the water, nutrients that otherwise might bewashed away. Some of both the nitrogen andnutrients are stored in the living plant matteruntil the fern/algae mat is incorporated into thesoil and begins to decompose. Because it hasa high lignin content, azolla decomposes rela-tively slowly—6 weeks or more before all thenutrients are released. This natural slow re-lease is ideal for a developing rice crop.

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In addition, it seems that azolla suppressesthe growth of certain aquatic weeds—in partbecause the thick azolla mat deprives youngweeds of sunlight and in part because the in-terlocking mat physically inhibits weed emer-gence. Rice seedlings are not harmed because,when transplanted, they stand above the azollamat,

Using any green manure crop requires someadjustments in a farmer’s crop managementsystem. Depending on the local environments,azolla can be grown as a monocrop, intercrop,or both. If the fern is grown as a monocrop,it is grown and incorporated into the soil beforethe rice is harvested or it is grown and trans-ported for use on upland crops. Azolla is oftenintercropped in areas where the growingseason is too short for successful monocrop-ping. One method grows two rows of riceplanted about 4 inches apart with Azolla grow-ing in two-foot spaces on either side of the dou-ble rows. The azolla is incorporated by handor with a rotary rice weeder. Combining mono-cropped and intercropped azolla provides ni-trogen before transplanting and throughout thegrowing season. At present, azolla’s primaryrole is as a spring green manure and its sec-ondary role is as a fall manure. It is highly sus-ceptible to pests and temperature extremes andgenerally is not grown crops in summer.

To be successful, azolla requires phosphorusfertilizer (0.5 to 1.0 kg P/ha/week), but this isnot necessarily an increase over the fertilizerneeded to produce a rice crop. Rice also re-quires phosphorus; so, rather than applying itdirectly to the rice the fertilizer can be givento the azolla in small weekly doses. Once theazolla is incorporated into the soil and beginsto decompose, the phosphorus becomes avail-able to the rice crop. Other inputs that enhanceazolla growth in certain soils (e. g., potassium)are usually also applied for a high-yielding ricecrop and so can be cycled in a similar way.

Water is the primary environmental con-straint on azolla cultivation. As a freefloating,aquatic fern, azolla can only grow in areas withabundant, stable water supplies. Although itcan last for months under refrigeration, the

plant cannot survive for more than a few hourson a dry soil surface under direct summer sun.The azolla varieties available are not very stresstolerant; azolla cannot live in water outside a0° to 400 range, and for adequate growth thedaytime temperature should stay within 150 to3 5 00 C. Humidity and pH also affect azollagrowth.

Because the technology to grow azolla fromseeds (spores) does not exist, some plants (1 to10 percent of those needed for startup) mustbe maintained throughout the year. Because ofazolla’s sensitivity to temperature stress, theoverwintering and oversummering periods arecritical. The plant is also susceptible to a num-ber of insect and disease pests. The pests areespecially destructive during the summer andmust be carefully controlled. In fact, the pri-mary reason why azolla is not cultivated dur-ing the summer is because of the destructioncaused by rampant insects.

There are also cultural and economic con-straints on azolla cultivation. As with any in-novation, it can be difficult for people to ac-cept an idea that is foreign to their traditions.The idea of growing an aquatic legume is fun-damentally different from most farming soci-eties’ norms; and in many hungry countries,the idea of growing a crop just to plow it underseems utterly impractical. Azolla cultivationmay be slow in gaining acceptance, too, be-cause it demands a year-round commitmentnot usually required of rice farmers, And be-cause azolla cultivation is not applicable inareas where rice is broadcast-sown, it is not aviable technology for those regions that do notplant rice in rows,

Finally, social and political factors can workboth for and against azolla’s use, In some re-gions, especially where there are unfavorableland ownership patterns, low prices or otherstrong disincentives, farmers are not willingto shift from their immediate-subsistence,“plant and harvest” approach, because they donot see the long-term benefits. Political sys-tems, too, can have an effect. The successfulazolla programs in China and Vietnam dependheavily on specially trained “azolla teams”

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made possible by the structure of their farm-ing communes and cooperatives. Societies lesscentrally organized could have difficulty adopt-ing and transferring azolla cultivation tech-niques.

One of the major constraints on the devel-opment of azolla technologies is simply lackof information. Although it is an ancient agri-cultural system, its use has always been limitedand it has not received much scientific atten-tion. Research efforts are disorganized, scat-tered, and often repetitious. There has neverbeen an international discussion of azolla re-search priorities. And once again, traditionalsegmented research approaches have proveninadequate because many of the problems thatremain require a multidisciplinary approach.

As of 1980, azolla was cultivated as a greenmanure on about 2 percent of the harvestedrice area of China and about 5 percent of thespring rice crop. In Vietnam, azolla grows asa winter green manure for 8 to 12 percent ofthe total harvested area, and about 40 to 60 per-cent of the irrigated spring rice in the Red Riverdelta. But these two countries are only two ofmany that might tap azolla’s potential. With re-search, strains could be found that are less sen-sitive to summer insects and temperature andcultivation could increase substantially. Inessence, using azolla in rice production ex-changes labor for nitrogen fertilizer. In coun-tries with a shortage of cash but plentiful la-bor, azolla technology could be a step towardsustainable agriculture productivity.

Underexploited Animal Species

People interested in helping developingcountries better their standards of living tendto promote resources and technologies withwhich they already have experience. One hearsmuch, for example, of how genetic engineer-ing can be expected to make possible self-fertilizing varieties of conventional crops suchas wheat and corn. While understandable, thispreoccupation with increasing the productivityof “mainstream” species overlooks a vast po-tential. Indigenous species often have the

advantage of being relevant to the customs andvalues of local people.

Just as there are unfamiliar plants ripe fordevelopment as sources of food, feed, fiber, andfuel, so are there also unfamiliar animal spe-cies at least as promising. People traditionallyhave relied on a small number of animals thathave been domesticated since prehistorictimes. But domestication of some different spe-cies could pay tremendous dividends. In somecountries, in fact, this is already beginning.

For instance, small animals are particularlysuited to domestication in many developingcountries because they require little space, theyfit well into village or urban life, and they re-quire no refrigeration since they can be eatenin one meal. Moreover, many of these speciestolerate the climates of developing countriesbetter than do sheep, cattle, and pigs, and theythrive on readily available diets. Thus, snailfarming in Nigeria, giant toad farming in Chile,and guinea pig farming in Peru are all beingdeveloped to provide native people with much-needed high-quality protein at affordable costs.

In addition, at least some of these venturescan become the basis of new industries. Thanksto the efforts of researchers at the La Serenacampus of the University of Chile, for exam-ple, intensive methods have been developedthat furnish grocery stores, restaurants, andcanneries with 10 to 15 tons of giant toad legsa year. Because the meat is an attractive whiteand tastes like a blend of chicken and lobster,it could prove to be a lucrative export as well.Giant toads are reportedly easy and inexpen-sive to rear. Kept in isolated ponds (so that theywill not cannabilize other aquatic life) and sup-plied with insects attracted by flowers, shrubs,and rotten fruit, they require little attention andreach their market weight of about half a poundin 2 years.

The domestication of exotic species is, infact, already producing foreign exchange forat least one poor country—Papua New Guinea.There, people who used to hunt crocodiles inthe wild are now more profitably rearing hatch-lings in captivity for the world skin market.

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And in remote jungle villages butterflies are be-ing raised on “farms without walls” to meetthe rising international demand from mu-seums, entomologists, private collectors, or-dinary citizens, and the decorator trade.

Both the crocodile and butterfly projectsdemonstrate that development and the conser-vation of natural resources can go hand inhand. They also demonstrate something else:that to succeed, such projects need not only aconcern for development but also a sensitivityto local environmental conditions and knowl-edgeable inputs of science and sociology.

In Papua New Guinea, for instance, the in-troduction of western-style cattle ranchingcould threaten the fragile tropical forest eco-system. And such imported technologies wouldbe completely unfamiliar to local people. Bycontrast, crocodile and butterfly farming thatcan be based on sound biological principles,would make it worthwhile for local people touse indigenous renewable resources wisely.

Zeolites

Zeolites are natural, three-dimensional, fine-grained silicate minerals composed of alkaliand earth metals crystals that have an abilityto separate gas molecules on the basis of sizeand shape. Over 100 forms have been synthe-sized and are now the mainstay of multimil-lion-dollar molecular sieve businesses that areimportant for industrial purposes in chemicaland petrochemical firms in the United Statesand abroad.

Zeolites, however, also occur abundantly innature, Almost 50 species have been identifiedfrom volcanic sedimentary deposits on everycontinent. Their widespread dispersion andspecial properties make them of interest tocountries wishing to rely less on costly im-ported inputs to produce food because they ap-pear promising as a means to improve animalhusbandry, fish production, and crop yields.Zeolites have such promise primarily becausethey act as traps for nitrogen.

Zeolites get their name from the classicalGreek words “boiling stones” because they

froth when exposed to intense heat. Althoughtheir existence has been known to scientistssince 1756 and they have been used since an-tiquity as building materials, their potentialagricultural and aquacultural applicationswere virtually ignored until about 20 years ago.Even now this technology must be said to besuffering from neglect.

When added to animal feed, for example,zeolites have both inhibited the developmentof mold during storage and increased thegrowth rates of swine, rabbits, poultry, beef,and dairy cattle. Moreover animals raised onzeolite-enriched rations tend not to be subjectto diarrhea or other ills. These minerals arethus a possible alternative to the controversialuse of antibiotics in livestock feed.

Besides thriving on zeolite-supplementeddiets, animals fed these minerals produce ex-crement that is at once almost odorless and ex-ceptionally good fertilizer. This is becausezeolites capture the ammonia ion from the fe-ces and thus retain the biological availabilityof the nitrogen in animal wastes. Direct zeolitetreatment of manure to reduce odor and im-prove its efficacy as fertilizer is also feasible,as is using the adsorption properties of natu-ral zeolites to obtain pure methane for energypurposes from animal or other organic wastes.

In summary, the application of zeolites toanimal husbandry holds some promise fromthe perspectives of livestock production, pol-lution control, crop yields, and energy alter-natives.

Zeolite technology also has potential for thecommercial fish breeding and farming. For onething, the rations now fed to fish in such enter-prises are quite expensive. As the nutritionalrequirements of fish are similar to those ofpoultry, the indications are that zeolite supple-ments could be expected to reduce feedingcosts. For another, many fish species are raisedin closed or recirculating water systems wherethe accumulations of nitrogen from their wasteand the decay of uneaten food commonlycauses sterility, stunted growth, and high mor-tality. Although various means already are usedto deal with these problems, zeolite regulation

of the nitrogen content of fish ponds has beenreported to be cheaper and, under low temper-ature conditions, more reliable.

Similarly, the affinity of zeolites for nitrogenmay be important in ponds and small lakeswhere eutrophication results in an oxygen-poorenvironment detrimental to fish life. Evidencesuggests that the ability of these minerals to in-troduce free oxygen into stagnant water mightincrease the number of fish that can be raisedor transported in a given volume of water.

The properties of zeolites also improve theperformances of chemical fertilizers and pes-ticides, fungicides, and herbicides. For exam-ple, zeolite-treated soils retain the nutrientssupplied by chemical fertilizers longer thansoils treated with the fertilizers alone. The pres-ence of zeolites as soil conditioners (alsoknown as soil amendments) also has beenfound to regulate the release of critical nutri-ents from fertilizers. Improved yields of wheat,apples, eggplant, carrots, sorghum, radishes,chrysanthemums, and sugar beets have beenreported.

Controlled release of micronutrients from thesoil itself—e.g., iron, zinc, copper, manganese,and cobalt—has also been found when zeolitesare used in conjunction with chemical fer-tilizers; this also prevents them from cakingand hardening during storage.

Zeolites added to pesticides, herbicides, andfungicides seem to enhance their effectiveness.They can also be exploited to remove toxicheavy metals from the soil, thus preventing thetoxic wastes from moving up the food chainfrom plants to animals and, ultimately, topeople.

Nonetheless, the commercial use of zeolitesin agriculture has generally been on only a rela-tively small scale and then predominately inJapan and other parts of the Far East. Eventhough a number of domestic companies haveundertaken preliminary zeolite studies, little in-formation is available on the long-term bene-fits or adverse impacts of these minerals onfood production or the environment. Further-more, even such information as has been

developed is often proprietary. Though the de-sire of the private sector to keep its data con-fidential is understandable, this cannot help butlead to duplication of effort and slow progress.

Developing countries of course would beeager to reduce their costly dependence on im-ported fertilizers, fuels, and livestock feed. Co-operative ventures between the United Statesand these countries could improve knowledgeof zeolite technology and, importantly, under-take long-term or large-scale testing projectsunder field conditions.

Biological Nitrogen Fixation

One very promising multiple cropping strat-egy is the use of leguminous plants. Legumescan provide food, livestock fodder, and woodwhile concurrently improving soil fertility. Le-guminous plants—e.g., temperate species suchas alfalfa, soybeans, and clover—have the ca-pacity to provide their own nitrogenous fer-tilizer through bacteria (Rhizobia) that live innodules on their roots. The bacteria chemicallyconvert atmospheric nitrogen into a form thatthe plant can absorb and use. The nitrogen alsois available in the root zone for nonleguminouscompanion or follow-on crops to use.

The use of legumes is not new; generationsof farmers relied on rotations of legume plantsto restore nitrogen in the soil long before theadvent of cheap commercial fertilizers. Now,as energy costs skyrocket and fertilizer costsbecome prohibitive in many developing coun-tries, legume use—green manure—may be thebest remaining option for maintaining soil fer-tility and agriculture productivity.

Leguminous species could not only help pro-tect LDCS from burgeoning energy costs butcould also improve local nutrition. Nutri-tionally, legume seeds (beans or pulses) are twoto three times richer in protein than cerealgrains. Many have protein contents between20 to 40 percent. A few even range up to 60percent. This is particularly important becausethere is chronic protein deficiency in virtuallyevery developing country.

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Inoculant Technologies: Nitrogen can beconverted into forms usable by plants throughindustrial processes, but only at great cost,especially as energy prices escalate, But bio-logical nitrogen fixation (BNF) by symbioticassociations of plants with micro-organismsmay be an economically and environmentallysound approach to sustainable agriculture.

Farmers can capitalize in two ways on cer-tain plants’ innate ability to fix nitrogen bio-logically. First, of course, like countless pastgenerations of farmers they can use legumesin their cropping systems and benefit from thenitrogen produced, But recent innovations alsocan help farmers maximize nitrogen fixation.Using inoculant technology, selected legumescan be inoculated with specific strains ofRhizobium, the soil bacterium that associateswith legume roots and fixes nitrogen. This wayfarmers can more fully exploit the plant’s fer-tilizing capabilities.

Most soils harbor various native rhizobialpopulations and these strains will associatewith sprouting legumes. But because thesestrains differ greatly in their effectiveness, itcan be to the farmer’s advantage to plant leg-ume seeds that have been inoculated withproven strains of Rhizobium. The objective ofinoculation technologies is to introduce suffi-ciently high numbers of preselected strains ofrhizobia into the vicinity of the emerging rootso that they have a competitive advantage overany indigenous soil strains of lesser nitrogen-fixing ability.

Commercial-scale inoculant use is commonin the United States and Australia, Brazil,Uruguay, Argentina, India, and Egypt also pro-duce inoculants. But while demand for in-oculants is growing in many countries, it is notenough to simply import U.S. or other in-oculants because they may not be suitablyadapted to the LDCs climate, soils, and farm-ing systems. BNF can be improved by select-ing effective Rhizobium strains from the localenvironment and culturing these.

The major scientific constraint on develop-ing BNF technologies is inadequate under-standing of the interactions among specific

host legumes, rhizobial strains, and variousenvironments. This results in an inability topredict whether a given legume will respondto inoculation in a particular region. A lack oftrained personnel in tropical regions also actsto limit research and development efforts, Andbecause inoculant development and use re-quires some technical training, it may not bean easy technology for LDCs to adopt widely.But while legume use holds potential in allsegments of agriculture, inoculant technologyat present should only be advocated when thereis a known need to inoculate.

Most legumes in the Tropics fix about 100kg/ha/yr of nitrogen, although the forage treeleucaena can fix as much as 35o kg/ha/yr andsome other species can fix as much as 800kg/ha/yr. However, the benefit to nonlegumesis small when compared to the effects of nitrog-enous fertilizer as applied in the intensivecereal production systems of the developedworld. It is unrealistic to think that biologicallyfixed nitrogen will replace commercial fer-tilization of cereal and root crops. These cropsare known to respond to levels of nitrogen farin excess of those that could currently be sup-plied through legume BNF. Thus, it would beprofitable to determine ways to increase thecontribution of legume BNF as a complementto nitrogen fertilizers rather than as an alter-native.

Although legumes seem unlikely to replacecommercial fertilizers, fertilizer savings throughthe use of legumes could represent a signifi-cant savings in foreign exchange, reduce de-pendence on energy-rich nations, and lendmore stability and diversity to LDC agriculture.

Leguminous Plants: A great variety of legu-minous plants—both food crops and speciesuseful for fuelwood, fodder, and other needs—exist that could be cultivated in moist andarid/semiarid tropical climates, Winged beanis one extraordinarily valuable leguminous spe-cies. Tarwi, tepary bean, and yam beans arealso nitrogen-fixing species with potential inmoist tropical environments.

But not all leguminous species have highwater requirements. Adapted plant species

could be used in arid and semiarid regions aswell, serving not only to enhance land produc-tivity but also to stimulate depressed econ-omies. For example, leguminous trees such asAcacia, Leucaena, and Prosopis could be im-portant, fast-growing fuelwood sources. Be-cause 80 percent of the wood consumed in theThird World is used as fuel, and wood short-ages are of crisis proportions in some areas,the potential of agroforestry should not be un-derestimated,

In arid/semiarid regions, of course, wateravailability is a key factor in agricultural pro-ductivity. But problems are compounded insome dry environments because soils also havelow fertility. In these areas, drought-adapted,deep-rooted, nitrogen-fixing tree species (e.g.,Acacia albida and Prosopis cineraria), peren-nial arid-adapted herbaceous legumes (e. g.,Zornia and Tephrosia), and shrubby legumes(e.g., Palea species) could increase soil fertilityand triple water use efficiencies. By bolsteringsoil fertility with tree species, it is possible tocreate a system where production of foodstaples is water-limited rather than fertility-limited. And intercropping traditional, annualfood staples such as millet, sorghum, ground-nuts, and cowpeas with leguminous trees canactually stimulate crop yields.

Livestock fodder and cash crops, too, can beobtained from arid species. Arid-adapted, salt-tolerant shrubs (e.g., saltbush—Atriplex spe-cies), the pods of leguminous trees (e. g., Acaciatortilis, Acacia albida, and Prosopis species),and even cactus (Opuntia and Cereus) can ex-pand the amount of forage available for locallivestock while improving soil quality and en-hancing the stability of the grazed ecosystems.

LDC farmers also could benefit from grow-ing perennial, arid-adapted plants as cashcrops, The species Jojoba is under developmentin southern California, Arizona, Mexico, andvarious semiarid LDCs. It produces seed thatcontains a rancidity-resistant, nonallergenic,liquid wax with lubricating properties equiva-lent to oil from the endangered sperm whale.Another desert plant, guayule, contains natu-ral rubber and could become a major semiarid

crop. Other potential lies with various speciesof drought-adapted leguminous trees that mightbe useful for the gums they exude, cacti thatproduce table-quality fruits, and a number ofother innovative plant resources.

Surprisingly, relatively little work is beingdone to further current knowledge about someof these highly promising plant resources. Butas energy, fertilizer, irrigation, and other costsescalate, it seems inevitable that farmers in aridand semiarid regions will look more to adaptedcrops.

Optimal water-use efficiency in an arid/semiarid agroecosystem demands a mix ofnitrogen-fixers and water-to-dry matter conver-sion specialist plants. For instance, cacti area better supplier of the energy portion of live-stock feed than legumes because they have afivefold greater efficiency converting water todry matter, However, legume leaf litter is im-portant to create good soil fertility so the cactuscan achieve its maximum water-use efficiency.Thus, a mix of plants is needed. And becauselivestock need both energy and protein, bothenergy- and protein-producing plants are re-quired.

Similarly, appropriate use of arid-adaptedlegumes can increase fertilizer-use efficiency.Adapted legumes do not require nitrogen them-selves and when properly incorporated into adiversified agroecosystem they will reduce ni-trogen needs for nonlegumes as well. Manyarid-adapted plants, both legumes and non-legumes, have very deep root systems—anadvantage because they are thus capable of ex-tracting nutrients and minerals from deep sub-surface soil layers, Also, the deeper rooted spe-cies should capture a higher portion of anyfertilizers applied because the nutrients are notas likely to leach beyond their deep root zone.As an added benefit, wind and perhaps watererosion might be reduced, as many of theseplants are perennials and thus keep the soilmore adequately protected,

There are no major scientific constraints tousing arid-adapted plant resources in LDC agri-culture, but there is great need for expandedresearch and development efforts. The poten-

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tial paybacks could be great. Environmentalimpacts, too, are overwhelmingly positive, in-cluding the potential to slow desertification.

Political and social constraints, however, ex-ist that might limit the use of innovative plants.Cultural traditions, for instance, are not easilychanged and innovation must blend into ex-isting values systems and local behavior. If, asin Sahelian Africa, free-roaming goats devouryoung tree seedlings because tradition allowsthat goats can forage unrestrained, then refor-estation attempts must consider this and devisegoat-proof protection for the young trees.

Other social influences also can make theacceptance and use of innovation all the moredifficult. This is especially clear in researchcenters run by scientists either from or trainedin developed countries; consciously or not,they often strive to promote their own culturalvalues and ignore the methods and effective-ness of native farming systems, As was the casewith Acacia albida, the scientists may not bebroadly trained—the agronomists failing to seethe tree’s food potential and the foresters un-derestimating its potential because it does notgrow in forests and hence is not part of stand-ard sylviculture concepts. It is not lack of con-cern that causes this problem. Rather, someagricultural scientists tend to be overspecial-ized and limited in their experience. Also,administrative structures often thwart attemptsto develop integrated, innovative programs.

In practical terms, such innovative biologi-cal technologies offer real hope for LDC farm-ers. And the scale need not be big. A farmer,for instance, could plant 1 hectare with 200Prosopis trees at 15 cents each for a total costof $30. Land, a shovel, and buckets for water-ing the seedlings are the only prerequisites.With protein and nitrogen contents of 12,5 and2,0 percent, respectively, pods from the treescould in 2 or 3 years produce 60 kg of nitro-gen and return the $30 initial investment.

Many of the innovative systems now receiv-ing attention from the scientific community areactually widely used by subsistence farmers inthe developing countries, However, the plants

under cultivation now are of unselected geneticstock. It is comparable, in fact, to the use ofunselected races of maize and wheat that werein use in the late 1800s in the United States andEurope. Subjecting the innovative species toa rigorous research and development effortcould be expected to produce yield increases—perhaps twofold and threefold in 15 years—and other beneficial refinements of immensevalue to the people of the Third World. Andyield increases in tree legume production,fuelwood production, cash crop production,soil fertility, and ensuing staple food produc-tion would have repercussions throughout theeconomy—more income; greater demands forgoods; a larger tax base to support roads,schools, and health services; and increased em-ployment. By working within the bounds of theecosystems, innovative plant resources canhelp agrarian societies ensure sustainable andstable agriculture.

Mycorrhizal Fungi

Nitrogen is only one of the nutrients essen-tial to plant growth. So another approach toenhancing LDC agriculture without inputs ofcommercial fertilizers is to find ways to in-crease the effectiveness of the plant’s use of theother nutrients available in the soil.

Selective plant breeding, of course, still holdsgreat potential for developing varieties of inno-vative and traditional crops that are moreresistant to environmental stress. Geneticistshave made extraordinary strides in breedingvarieties that respond to commercial fertilizerinputs; similar efforts could help locate and de-velop plants that would grow and prosperunder less than ideal conditions—marginallands, variable climates, or deficient soils. Thispotential amplifies the importance of preserv-ing native plant resources, both in seed stor-age facilities and in their natural habitats, be-cause geneticists necessarily turn to hardy,native stocks as sources of genetic material toimprove cropped varieties.

There is another “biotic fertilizer” that mightaid LDCs in their quest for sustainable agro-

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ecosystems. Mycorrhizal fungi are beneficialsoil fungi that live symbiotically with a vastrange of plants. Mycorrhizae are the structuresformed—part plant, part fungus—by the sym-biosis. These structures can extend up to 8 cmfrom the root into the surrounding soil, pro-viding a bridge to transport nutrients back tothe roots, The host obtains nutrients via themycorrhizal fungi, while the fungus obtainssugars or other foods from the plant. The asso-ciation results in a marked increase in the hostplant’s growth.

There are many species of mycorrhizal fungithat form mycorrhizae and can enhance plantgrowth, These fungi are so common, in fact,that literally any field soil sample from the Arc-tic to the Tropics will contain some, The mostcommon type, vesicular-arbusula (VA) mycor-rhizae, occur on liverworts, ferns, some con-ifers, and most broad-leaved plants includingagronomically important species such as wheat,potatoes, beans, corn, alfalfa, grapes, datepalms, sugar cane, cassava, and dryland rice.Only 14 plant families are considered primar-ily nonmycorrhizal.

The fungi essentially increase the surfacearea of the plant’s roots for absorbing nutrients.They actually can increase the plant’s absorp-tive area by as much as 10 times. The fungi alsoextend the host plant’s range of uptake; nutri-ent ions that do not readily diffuse through thesoil—e.g., phosphorus, zinc, and copper—canbe tapped from beyond the normal root zoneby the fungi. Absorption of immobile elementscan be increased by as much as 60 times by theplant-fungi symbiosis. perhaps the most impor-tant benefit provided by mycorrhizal fungi isincreased phosphorus uptake. They also stim-ulate plant absorption of zinc, calcium, cooper,magnesium, and manganese. Plant uptake ofmobile soil nutrients such as nitrogen andpotassium is rarely improved because normalsoil diffusion typically supplies adequate amountsof these regardless of root size.

Mycorrhizal fungi also can enhance watertransport, prevent water stress under someconditions, enhance salt tolerance, and in-

crease symbiotic nitrogen-fixing bacteria suchas Rhizobium.

The potential offered by mycorrhizal fungias biotic fertilizers, however, is not as vast asit might seem. Mycorrhizal fungi already occurin most soils and thus already grow in asso-ciation with most agronomic crop plants. Be-cause these fungi are so widespread, immedi-ate needs for inoculation are limited. Theinoculants currently available are for use ondisturbed sites (strip-mined areas where in-digenous mycorrhizal populations have beendestroyed), on fumigated soils (any forest orcrop nursery or plot that has been treated toremove soil-borne pests), and in greenhouses(because sterile soils lack native mycorrhizalfungi). In these situations, inoculation withmycorrhizal fungi has proven beneficial—e.g.,in fumigated sand or soil, VA mycorrhizalfungi will increase the growth of citrus, soy-beans pine, and peaches. Growth improve-ments also show in cotton, tomatoes, corn,wheat, clover, barley, potatoes, and many othercrops.

But even though large-scale field inoculationswith mycorrhizal fungi are rare because of ade-quate indigenous populations and becausethere is limited inoculum available, it seemslikely that such applications might be muchmore valuable if, for instance, scientists de-velop mycorrhizal fungi inoculants that aresuperior to native populations. Because manyindigenous mycorrhizae are relatively ineffi-cient symbionts, improved strains of fungicould enhance plant growth, even in nonsterilesoils. And because huge expanses of tropicalsoils (e.g., the Brazilian Cerrado) are either defi-cient in phosphorus or immobilize added phos-phorus fertilizers, mycorrhizal fungi could im-prove the productivity of the marginal lands,if fungi having the ability to extract small quan-tities of fertilizer were developed and addedto the soil.

Even though mycorrhizal fungi inoculantsare used commercially in some circumstances,their importance is limited and many questionsabout their effectiveness remain unanswered.

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For instance, fumigating fields with methylbromide, a biocide that is extremely toxic tomycorrhizal fungi, often is followed by stuntedgrowth in following crops. Yet little work hasbeen done to determine the feasibility of field-scale application of inoculants. And even innursery crops grown on sterile, nonmycor-rhizal soils, inoculations receive limited use inpart because detailed information regardingtheir value is lacking. For tree crops, however,some of the answers may be coming; the U.S.Forest Service is conducting a testing programusing commercial inoculum on tree nurserysites throughout the country. When the testsare complete they should indicate the commer-cial feasibility of producing and using mycor-rhizal inoculum in fumigated tree nurseries.

Three major obstacles hinder further devel-opment of this biotic fertilizer, First, no large-scale field experiments using mycorrhizalfungi under normal agricultural conditions

have been conducted, yet such work is a nec-essary forerunner to actual use of the fungi,Second, cost-benefit analysis is warranted todetermine the economics of mycorrhizal ap-plications. And finally, agriculture itself mustshake loose of some conventionality; it seemslocked to practices for increasing soil fertilitythat only involve use of commercial chemicalfertilizers.

Because mycorrhizal fungi increase the effi-ciency of fertilizer use, they can be thought ofas biotic fertilizers and might be substituted forsome fertilizer components. Considering esti-mates that 75 percent of all the phosphorus ap-plied to crops is not used within the first yearand thus reverts to forms unavailable to plants,especially in tropical soils, it appears that fur-ther work on improving mycorrhizal fungi ef-fectiveness could aid LDCs in developing sus-tainable agricultural systems.

Chapter II

The Role of the Agencyfor International Development

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Page

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Budget and Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Current Innovative Biological Activities at AID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Two Approaches to Apply Innovative Biological Technology to

LDC Agricultural Problems . . . . . . . . . . . . . . . . . . . + +, . . . . . . . . . . . . . . . . . . . . . . . . . 25The Need for Cooperative Ventures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26The Need for Field Demonstrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., .,,,.. 26The Need for Innovative Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . 26The Need for Flexibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,., 27The Need for Trained AID Staff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., 28

Perceived Constraints ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Mission Agricultural Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , , . . . . . . . . . . 28CGIAR ......,.. . . . . . . . . . . . . . . . . . . +, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Agricultural Staff. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Summary of workshop Suggestions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30AID Organizational Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

List of Attendees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Chapter

The Role of the Agencyfor International Development

INTRODUCTION

During the second day of the workshop, AID discussions were candid and are summarizedstaff reviewed their agency’s agricultural de- in the following text. An organizational chartvelopment activities and the various con- in effect for AID in November 1980 appearsstraints under which AID operates when car- at the end of this chapter.rying out its agricultural mandates. Their

BUDGET AND G0ALS

In 1980, AID carried out about $600 millionin agricultural projects and research related tosolving agricultural problems and developingagricultural opportunities in LDCs. Further,AID spent an additional $43 million to trans-fer fertilizer, much of it going to Sri Lanka,Zambia, and Bangladesh.’ During the firstquarter of FY ’81, fertilizer transfers to India,Kenya, Zambia, and Bangladesh were $105 mil-lion. AID’s main thrust in agriculture is to helpLDCs increase agricultural productivity, espe-cially of the locally accepted basic food crops.By doing so, AID’s goal is to help LDCs im-prove their economy, nutrition, and the gen-eral well-being of their people,

But for AID to step beyond traditional ap-proaches and promote innovative technologiesto solve LDC food and agricultural problemsis risky. AID is not a research agency; its goalis development. Therefore, AID commonlysupports research that holds promise of highimmediate payoff and tends to avoid research

IA I D’s flna ncerf fert i]izer purchases for F}r ’80 were at the lowest levelsince 1965,

that may have long-run payoffs. Similarly, AIDfeels that its development projects should focuson the short term, have high visibility, andshow positive results quickly. It is not surpris-ing that some AID agriculturalists believe that“when you only have $2 to bet you don’t gofor long shots. ” To compound the problem,AID’s small budget for innovative activities isoften one of the first targets during budget cuts.

The United States, on the basis of its grossnational product (GNP), in 1980 ranked 14thof those countries that provide developmentassistance to LDCs. For example, Sweden con-tributes 1.0 percent of its GNP whereas the U.S.contributes 0.19 percent.

AID’s budget dilemma is complicated furtherby a growing list of competing developmentneeds such as forestry, women-in-development,and environmental concerns. AID has beenmany things to many people, but it has not beenperceived by Congress as a technical transferagency. AID stressed that there remains a lackof understanding among the public and Con-gress about how science and technology relateto economic development.

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CURRENT INNOVATIVE BIOLOGlCAL ACTIVITIES AT AID

During the workshop, AID participants pre-sented a brief overview of some of their cur-rent activities involving various innovativebiological technologies. Examples includedbiological nitrogen fixation, tissue culture, andapplied soybean research. In addition, througha collaborative effort, AID, the Joint ResearchCommittee (JRC), the Board on InternationalFood and Agricultural Development (BIFAD),and 30 land-grant colleges and universitieshave developed three Collaborative ResearchSupport Programs (CRSP) to study smallruminants, sorghum and millet, and bean/cowpea production systems. The activities involve30 U.S. universities, six international agricul-tural research centers, and one foundation.Work is carried out at 28 LDC sites with col-laboration of the local LDC institution. Twonew CRSPs are being developed in nutritionand soils. These activities will expand the num-ber of participating U.S. universities by eightand LDC sites by ten.

CRSPs are viewed as long-term researchendeavors, at least five years in duration. AIDfunds up to 75 percent of the CRSP and thecollaborating U.S. colleges and universitiescontribute from 25 to 50 percent. At least 50percent of AID’s CRSP budget is spent in par-ticipating countries. AID’s minimum budgetfor FY ’82 CRSP activities is $11 million. AIDplans to invest a minimum of $88.3 million inCRSP activities from FY ’82 through FY ’87.

Biological nitrogen fixation (BNF) is not anew technology; it was recognized in Biblicaltimes that when certain legumes were grownin alternate years, the yield of the followingyear’s crop was improved. After five years ofresearch, AID recognizes that BNF technologystill could be improved. Because it can providenitrogen to plants in a usable form without theexpense of commercial nitrogen fertilizers, ithas important potentials for LDCs and devel-oped countries alike.

Rhizobia, nitrogen-fixing bacteria that live innodules associated with the roots of certainplants, can be used in some instances to in-

oculate the roots of plants to enhance nitrogenproduction. No infallible technique to inoculateseeds is known, but this is an area of researchAID is addressing. (The information of BNFsummarized elsewhere in this report is basedon research at the University of Hawaii spon-sored in part by AID). BNF in tropical grassesalso is being studied. AID is working on in-country testing of BNF technology, building in-oculation production and distribution systems,developing profitable BNF cropping systems,and providing continued help in improvingBNF technology for LDC use.

AID believes that commercial fertilizers playan important role in LDC agriculture but alsobelieves that BNF technology can help thesecountries reduce their need for commercial ni-trogen fertilizers. Considering that commercialnitrogen fertilizer may cost as much as $1 apound by the year 2000, BNF, which ultimatelymay reduce the need for commercial nitrogenfertilizers in LDCs by 25 percent, could helptremendously.

AID is supporting some research on tissueculture to supplement its traditional researchon standard crop-breeding practices. AIDbelieves tissue culture to be an inexpensivetechnology and one that has good potential foruse in LDC agriculture.

In the past, agriculturalists selected superiorplants for reproduction by handpicking thosefew individual plants having certain desirablecharacteristics out of many thousands of theless desirable specimens. Space and timeseverely limit the number of plants screenedthis way. With tissue culture, desirable plantscan be selected and propagated quickly andeasily. For example, an agriculturally desirableplant can be used as a cell source for a desiredspecial characteristic such as salt toleranceneeded for growth in irrigated areas. A tinyslice of the plant can be used to grow largeclusters of cells that can be separated in thelaboratory and screened to find the cells hav-ing the required characteristics. These cells inturn can be grown to full plants that themselves

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can be used for seed sources. Research hasdemonstrated that the new plants will survivethe particular soil stresses for which they werescreened. This technique enhances our abilityto design plants for the especially harsh envi-ronments in LDCs and holds real promise forimproving LDC agriculture.

AID provides support for the InternationalSoybean Program (INTSOY) as part of its ef-fort to support innovative biological technol-

ogies. INTSOY works to improve and adaptsoybeans for tropical developing countriesthrough germplasm selection. Some of their ap-plied research deals with finding improvedways to store seed for extended times in LDCsand improving soybean processing using sim-ple technologies. INTSOY also is studying therole of soybeans in the LDC farming economiesand in the national economy as well.

TWO APPROACHES TO APPLY INNOVATIVE BIOLOGICALTECHNOLOGIES TO LDC AGRICULTURAL PROBLEMS

Two sharply different approaches to apply-ing innovative biological technologies to LDCagricultural problems, particularly the problemof rising fertilizer costs, surfaced during theworkshop’s discussions. The first might becalled an “agroecosystem approach” and wasstressed by most non-AID participants. Thesecond reflected a “conventional productionapproach” and was mainly an AID viewpoint.

The “agroecosystem approach” focuses onapplying biological technologies that are tai-lored to fit the biological, physical, and sociallimitations of the local environment so thatsustainable agriculture can exist within theconstraints of the natural resource base. Thisapproach includes a concern for energy con-servation and a desire for interdisciplinary re-search and development.

The “agroecosystem approach” to LDC re-quirements for food, fodder, and fuel alsofocuses on developing new agricultural sys-tems and on accepting rediscovered, and per-haps improved, agricultural systems. A widespectrum of agricultural crops is consideredincluding a number that might be viewed asnontraditional. This approach emphasizes re-storing, maintaining, and improving the natu-ral resource base while offering the farmers areasonable chance for economic betterment.

In comparison, the “conventional productionapproach” stresses production and increasedyields. It tends to focus on a more limited num-

ber of crops for which a market already exists.The ecosystem is adjusted to provide high pro-duction of these crops by using intensive in-puts of commercial fertilizers, pesticides,pumped water, and petroleum-powered farmequipment. Some such systems commonly arecategorized as “green revolution” technologies.Major efforts have been devoted to mainstaycrops such as rice, corn, sorghum, and soy-beans, and production increases generally havebeen outstanding.

The variety of crops dealt with in this ap-proach is more limited than in the “agroeco-system approach” and monoculture often areeconomically advantageous. Production effortstypically attempt to foster crop growth by over-coming local environmental constraints suchas infertile soils or water scarcity. In manycases the technologies promoted are adapta-tions of technologies that have been used suc-cessfully in developed countries and temperateclimates.

There are, of course, instances where the twoapproaches overlap, but these are exceptions.Proponents of both approaches are trying tohelp LDCs improve the well-being of the popu-lace—their methods, however, include quitedifferent agricultural styles and practices. Theworkshop focused on the opportunities shownby each of the approaches for helping LDCs re-duce their need for expensive commercial fer-tilizers while enhancing soil productivity.

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The Need for Cooperative Ventures

Participants agreed that agricultural researchand its appropriate implementation in lesserdeveloped countries is an AID/LDC coopera-tive venture and that good communication isessential for success. They discussed the in-herent difficulties involved in using U.S. ex-pertise in LDC projects because many U.S.experts lack the special training that is appro-priate to the physical and biological environ-ment. Many U.S. technical experts used by AIDare drawn from U.S. land-grant universitiesand consulting firms where there is littlefamiliarity and experience with LDCs. And be-cause the United States historically has littleexperience in LDC—i.e., tropical—agriculture,AID has difficulty finding contractors who areable to grasp LDC agricultural problemsquickly and recognize the appropriateness orinappropriateness of temperate region agricul-tural solutions.

AID has provided grants and other supportto numerous U.S. universities to help them de-velop their teaching/research expertise so thatit can be tapped to help solve LDC agriculturalproblems. Many of these universities have setaside land for use in agricultural research andteaching, but again agricultural research re-sults commonly are not readily transferablefrom region to region. Further, because pilotstudies often are cumbersome to conduct, takeconsiderable time, and lack significant recog-nition, few university scientists are eager todevote effort to projects relevant to LDC agri-culture, even though certain aspects may alsohold indirect promise for improving U.S. agri-culture.

The Need for Field Demons-rations

Pilot projects, demonstrations, and field ex-periments carried out in LDCs by U.S. andhost-country interdisciplinary teams on inno-vative biological technologies are essential firststeps before new technologies can be usedwidely. Section 103A of the Foreign AssistanceAct directs AID to carry out pilot studies. Fur-ther, workshop participants agreed that the pri-vate sector, whether U.S. or LDC, should be

encouraged to participate in biological technol-ogy development and its transfer to potentialusers. Only where new technologies can beshown to be economically profitable is therethe likelihood of their being pursued andadopted by the private sector. For example,Thailand established several innovative pro-grams in alcohol production from cassavathrough direct links between the private sec-tor and Thai research institutions. It was alsopointed out that in many places, farmers learnnew agricultural techniques from salesmen.

AID believes that during the 1980s it will em-phasize technology transfer but hopes to spon-sor increased adaptive field research and docooperative research with LDC scientists. TheAgency sees the need for multitiered develop-ment efforts but recognized the difficulty in co-ordinating them. There is an acute need forLDCs to establish their own national researchpriorities rather than having the donor com-munity do so.

pilot-scale activities that receive partial sup-port from AID do exist at the international agri-cultural centers. But whether or not all suchinstitutions strongly emphasize the “agroeco-system approach,” especially agricultural tech-niques that are aimed at enhancing soil fertilityand reducing reliance on expensive commer-cial fertilizers, was debated. AID believes thatmuch of the work carried out at the interna-tional centers is innovative, but many of thenon-AID participants felt that these centers paylittle attention to low fertilizer, low-energy agri-cultural systems,

The Need for Innovative Research

Further, AID was criticized for spending $43million of its $650 million agricultural effortson the transfer of expensive commercial fer-tilizers to LDCs without providing incentivesto try new agricultural methods that minimizefertilizer use. LDCs must develop the resourcesto continue appropriate fertilizer use, but alongwith this should go development of efficientnew agriculture systems that rely on biologi-cal processes to complement soil nutrient avail-ability. The use of mycorrhizal technologies,

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for instance, seems to hold great promise forreducing fertilizer needs, but AID is not work-ing with this technology, Although AID agri-cultural professionals in the Development Sup-port Bureau have tried to initiate mycorrhizalresearch, it has failed to place high enough ontheir priority list to warrant funding in eachof the last two years. AID interest in biologi-cal technologies has expanded, but the Agencystaff feels funds remain the limiting factor.They feel their involvement in biotechnologyresearch might help speed transfer and imple-mentation of its results.

Workshop participants encouraged AID toplace agricultural scientists from nonconven-tional fields of study on AID peer review panels,of field projects and research activities. Be-cause AID seemed committed to conventionalagriculture, some workshop part icipantsbelieved that AID needs fresh ideas to helptheir agricultural professionals move awayfrom conventional paths and into new areashaving potential for high payoff for LDCs.AID’s peer review was likened to “an old boysystem, ” one in which acceptance of new ideaswas slow, Non-AID members also viewed theU.S. Department of Agriculture (USDA) dimlyin the field of innovative biological researchbecause they felt that USDA, too, primarily iscommitted to conventionality. Some partici-pants thought USDA was not helping AID withthe question of how to maintain productivesoils in LDCs while reducing the input of ex-pensive commercial fertilizers.

In the view of “agroecosystem” proponents,AID and some international agriculturalcenters place the greater part of their effortson a few traditional food crops but do little todevelop underexploited, nutritionally impor-tant new food crops, AID was viewed as hav-ing no interest in these “odd-ball” crops eventhough such foods contribute significantly toLDC diets. Proponents of the “agroecosystemapproach” proposed looking into any foodcrops that fit into the local ecological system,Therefore, the resulting mix of crops might beradically different from the crop mix recom-mended by the “production approach, ” but one

that could be sustained with lower fertilizerinputs,

An agroforestry system might be institutedthat would integrate, for example, tree cropsfor food, fodder, firewood, and erosion control;native food crops; microbiological systemssuch as mycorrhiza and rhizobium; and localmineral resources such as zeolites into a low-energy consuming system. Participants en-couraged AID to set aside a certain percent-age of its appropriations each year to look fornew, low-energy agricultural systems. TheAgency could continue to back its efforts in“bread and butter” crops—corn, rice, etc.– butshould be willing to commit some of its re-sources to nonconventional approaches. Allparticipants agreed that AID should be en-couraged to take some risks and not merely toback “winner” crops,

The Need for Flexibility

Most non-AID participants, as well as someAID staff, believed that the Agency needs amore flexible mechanism to provide fundingfor small-scale innovative activities. Currently,AID seems unable to transfer small amountsof money quickly or easily for such projects orexperimental activities. The Agency claims thatprocessing a small amount of money is as time-consuming as processing large grants or proj-ects. Pressure within AID to obligate programdollars rapidly makes dealing with small proj-ects bothersome. AID’s agricultural profes-sionals in the Development Support Bureau,for example, may wish to support certain in-expensive innovative activities, but they arediscouraged by internal AID procedures andthe program office’s strong control, Conse-quently, scientists outside of AID who havespecial useful knowledge and who wish to par-ticipate in solving LDC agricultural problemsfeel that AID is neither open nor interested inoutside assistance, Yet most participants feltthat many aspects of both the “conventionalproduction approach” and “agroecosystem ap-proach” could be integrated with positiveresults.

38-846 0 - 85 - z

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The non-AID scientists elaborated on how itis generally difficult for them to obtain neededsupport for innovative approaches to low-energy agricultural systems. The picture wassimilar for the varied researchers. First, thereseems to be little support for funding the broadrange of innovative biological technologies thatmay help improve LDC agricultural systems,This is particularly true at most U.S. univer-sities because the universities find it difficultto support international activities that seemremote. Then, too, researchers who rely on theuniversity for their salary commonly do notwant to jeopardize their security by conduct-ing nonmainline research.

Some of the non-AID researchers admittedthat to carry out their chosen areas of LDC-related research they sometimes resort to usingsmall amounts of money from other projectsthat are not LDC-related (“bootlegging”). Othercommon small funding sources for LDC-re-lated research include a variety of Federalagencies other than AID, although AID doesprovide significant support for the biologicalnitrogen fixation work at the University of Ha-waii. An AID grant provides partial support forazolla/algae research. Because Federal supportfor LDC-related research has the habit of

vanishing suddenly, non-AID researchers faceconstant doubt about the continuity of theirfunding. The National Science Foundation,some United Nations institutions, small univer-sity grants, and private industry and institu-tions sometimes are funding sources as well.Private industry support seemed lacking for ap-plied research in these fields.

Underlying all of the above problems was thestrong need for a significant increase in thenumber of technically trained professionals inagriculture and natural resource areas in AIDand its Missions overseas. Existing technicalprofessionals need to spend increased time onthe substance of their projects and less deal-ing with bureaucratic constraints. Withoutsuch an environment, AID may find it increas-ingly difficult to maintain or expand technicalcompetence within its Washington offices orMissions in LDCs. A need for improved com-munication between scientists and the Con-gress was restated several times during theworkshop, and activities similar to this work-shop were cited as a step in the right direction.

PERCElVED CONSTRAINTS

AID’s major efforts in innovative agriculturalresearch are directed primarily to the 13 inter-national agricultural research centers to whichAID contributes financial support. Much of theAID activity, however, depends on the workof the AID Missions and the ability of the pro-fessional staff to relate to the scientific com-munity at large and to the Missions and re-gional or geographic bureaus. A number ofproblems in these areas were identified by theworkshop participants.

Mission Agricultural Activities

AID Missions largely are removed from cur-rent science and technology developments inthe academic and private sectors. Conse-

quently, AID faces a difficult task in channel-ing new science and technology to field activ-ities in most LDCs. In addition, AID staff at theworkshop explained that many Missions feelthat adequate technology already exists andthat new science and technology are notneeded. The Missions want AID technical peo-ple to solve the problems that the Missionsidentify using established technologies. Thisapproach frustrates AID professional staff, in-cluding staff in the Agriculture Office.

AID considers its contribution to the Con-sultative Group on International AgriculturalResearch (CGIAR) valuable and feels that the

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nonbureaucratic institution functions very wellin addressing agricultural development prob-lems and in implementing research results.AID sees Korea as a model of successful de-velopment where effective technology transferhas occurred, and feels that the Korea exam-ple should be used as a model for developmentactivities by other LDCs.

Agrcultural Staff

AID agricultural professionals attempt tomaintain close contact with agricultural ex-perts in the scientific community both withinand outside of USDA. But the number of agri-cultural scientists in AID is so small that main-taining regular contact with their scientific col-leagues can be difficult. AID employs about4,000 people yet its Development Support Bu-reau (DSB), the bureau that provides technicalsupport to all of AID’s regional or geographicbureaus, has only 25 agricultural professionals.These 25 people managed about $70 million inagricultural projects in FY ’80. Further, onlyabout 10 percent of AID Mission personnelworldwide are agricultural officers eventhough some 50 percent of AID’s developmentprograms are agriculturally oriented. BecauseAID commonly reassigns its agricultural pro-fessionals to new Missions or back to the U.S.about every three to four years, many agricul-tural programs suffer from the lack of conti-nuity. AID’s workshop participants felt person-nel rotations occur too frequently.

AID workshop participants felt that theAgency’s emphasis on natural resource man-agement should be increased but that this areais not receiving much Agency attention. Nat-ural resource management requires an inter-disciplinary approach, but because AID issegmented into numerous administrative com-partments it is extremely difficult to conductinterdisciplinary activities. For example, agro-forestry activities were to be transferred re-cently to DSB’s Office of Forestry, Environ-ment, and Natural Resources, the successor tothe Office of Science and Technology (OST).Agroforestry, by definition, combines aspectsboth of agriculture and forestry, yet in the new

arrangement, agroforestry is separated fromagriculture.

The mandate to identify and test innovativeand/or emerging science and technology andto transfer promising ideas to AID’s Missionsand Regional Bureaus belonged to the dis-banded Office of Science and Technology. Thisoffice served as AID’s “window” to the scienceand technology community and gave AID theopportunity to tap a broad array of innovativescience and technology to help solve LDCproblems. 2

A problem that AID workshop participantshighlighted repeatedly was that of the ex-panded role of AID program officers in deci-sionmaking and priority-setting for agricultureprojects and research. Program officers com-monly are generalists having little or no tech-nical agricultural training. Organizationally,they sit between top bureau administrators andagriculturalists and other professionals and ex-ert a strong influence on AID’s agricultural ef-forts. AID agricultural professionals feel thatthey are continually second-guessed by pro-gram office generalists and that the technicalcontent of proposed agricultural projects andresearch many times is adversely affected bythe actions of the program office.

Program officers commonly evaluate projector research activities. But AID’s evaluationprocess seems to foster a strong desire to haveevaluations that show positive results. Withoutpositive evaluations, the difficulty of movingsubsequent projects through the AID systemand, therefore, through the program office mayincrease. This perception, whether true or not,discourages some technical professionals frompursuing innovative opportunities because theelement of risk in innovative activities gener-ally is higher than in traditional approaches.The overall effect of having an inordinatelystrong program office is that agricultural pro-fessionals introduce fewer innovative technol-ogies into AID agricultural programs.

‘As of May 1981, a new Bureau for Science and Technology was formed.(See section on AID organization changes.)

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Fall 1984

Demand for the original House Foreign Af-fairs Committee publication on innovativebiological technologies was high in the UnitedStates as well as many other countries and by1984 copies were no longer available. Con-tinuing requests for the publication have pro-mpted OTA to reprint the document in itsworkshop series. Described below are somerelevant policy changes that have occurred atAID since the 1980 workshop.

The atmosphere at AID today is more fa-vorable toward new biological technologies.The current administration has expandedwork on tissue culture and sees potential inother related areas. The attitude toward inno-vative crops, however, remains essentially un-changed and few resources are directedtoward new crop development.

In its overseas Missions and within AID-Washington, there is still a scarcity of profes-sional agriculturalists. Those that are on staffhave many, diverse responsibilities so thatinnovative biological technologies do not re-ceive much attention. Nevertheless, the Na-tional Academy of Sciences Board on Science

Addendum

and Technology for International Develop-ment (BOSTID) receives AID funds to seeknew biological opportunities for developingcountries. Since the 1980 workshop, researchreceived increased attention in AID, however,the substantial budget cuts recently proposedin 1985 may adversely affect this trend.

One problem identified at the 1980 work-shop concerned AID’s inability to supportsmall scale activities. AID appears to have im-proved some in this area. A new small grantsprogram—the Program in Science and Tech-nology Cooperation (PSTC)—has been estab-lished in the Office of the Science Advisor.The program is designed to stimulate new out-side research on problems that confront de-veloping nations. Priority funding is directedto five areas: Biotechnology/Immunology,Plant Biotechnology, Chemistry for WorldFood Needs, Biomass Resources and Conver-sion Technology, and Biological Control ofDisease. This type of competitive, small grantsprogram is an important step toward provid-ing a more flexible mechanism to supportinnovative and small-scale research and tech-nology development.

SUMMARY OF WORKSHOP SUGGESTIONS

Summarized below are a variety of sugges-tions generated by the 40 participants duringthe course of the workshop discussions. Someof these topics received considerable attentionand others much less. The participants wereencouraged to express their points of viewfreely on any issues they felt were relevant. Bydoing so, the participants touched upon a va-riety of topics, many of which deserved moredetailed examination than could be accom-plished in two days. The issues that surfaced,however, should help the House Committee onForeign Affairs in their oversight responsi-bilities of the Agency for International Devel-opment and in determining the role that inno-vative biological technologies could play inenhancing soil fertility, improving food pro-

duction, and reducing the need for expensivecommercial fertilizers throughout the world.

*

*

*

AID should greatly increase the number ofin-house agricultural professionals in Wash-ington and in the missions, especially indecisionmaking positions.AID should increase the number of Missiondirectors who are agricultural professionals.Similarly, effort should be made to encour-age the selection of an increased number ofpeople with professional agricultural train-ing as ambassadors for LDCs.AID should encourage the U.S. and LDC pri-vate sector to participate in pilot-scale proj-ects testing and developing innovative bio-logical technologies.

—

*

*

*

*

*

AID should appoint some outside experts innonconventional agricultural technologies toits advisory committees and to its peer re-view panels.AID should broaden its inventory of scien-tists who might help AID expand its effortsinto nonconventional agricultural practices.AID should streamline its procedures to en-courage increased outside participation byU.S. scientists and technologies in small-scale innovative agricultural activities.AID should set aside a certain percentage ofeach agricultural project to integrate somenew, innovative biological technology intothe project.AID should fund some small-scale, pilot-typeprojects on the kinds of innovative biologi-cal technologies presented at this workshopand encourage the participation of outsidescientists to work on the project as membersof interdisciplinary teams. The need for pilottesting of a wide variety of innovative bio-logical technologies by AID was stressedheavily and the need for risk-taking was en-couraged.

*

*

*

*

AID should increase its activities in agro-forestry systems. These activities should beexpanded to include both humid tropical re-gions and arid/semiarid regions. Pilot testingof the arid/semiarid systems could be carriedout in the Southwest United States andLDCs,An expanded inventory of innovative bio-logical technologies that could help LDCs re-duce their need for expensive commercialfertilizers should be prepared, and institu-tions and individuals who have the skills forthese technologies could be identified.OTA could conduct a full assessment of abroad range of innovative biological technol-ogies that could help LDCs reduce the needfor their use of expensive commercial fer-tilizers.AID should emphasize the transfer of tech-nical information to LDCs and to AID mis-sion agriculturalists, particularly on innova-tive biological technologies that might helpLDCs reduce their need for expensive com-mercial fertilizers.

AID ORGANIZATION CHANGES

The Administrator for the Agency for Inter-national Development (AID) on May 21, 1981,announced a reorganization for the structureof AID (see following chart). One major changewas the formation of a new Bureau for Tech-nology and Science to replace the old Bureaufor Development Support. Structurally, thischange gives greater prominence to the role of

science and technology in AID than has existedpreviously. Unlike the other AID bureaus forScience and Technology. Unlike the other AIDbureaus which are headed by Assistant Ad-ministrators, the Bureau for Science and Tech-nology is headed by a Senior Assistant Admin-istrator, thus giving added strength to scienceand technology in AID.

32

AGENCY FOR INTERNATIONAL DEVELOPMENT

Authors

Dr. James DukeUSDA/ARSGermplasm Resources LaboratoryBuilding 001, Room 131BARC-WestBeltsville, MD 20705

Dr. Peter FelkerCeasar Kleberg Wildlife Research InstituteCollege of AgricultureTexas A & I UniversityKingsville, TX 78363

Dr. Jake HallidayBattelle KetteringResearch Laboratory150 East South College StreetYellow Springs, OH 45387

Dr. William LiebhardtRodale Research CenterRD1 BOX 323Kutstown, PA 19530

Dr. Cy McKellDirector of ResearchNative Plants, Inc.417 Wakara WayUniversity Research ParkSalt Lake City, UT 84108

Dr. John MengeFull ProfessorDepartment of Plant PathologyUniversity of CaliforniaRiverside, CA 92521

Dr. Fred MumptonDepartment of Earth SciencesState University CollegeBrockport, NY 14420

33

Dr. Donald PlucknettScientific AdvisorWorld Bank/CGIARRoom K10451818 H Street, N.W.Washington, DC 20433

Dr. Noel VietmeyerNational Academy of SciencesNational Research CouncilJH213 BOSTID2101 Constitution Avenue, N.W.Washington, DC 20418

Dr. Stephen R. GliessmanAgroecology ProgramBoard of Environmental StudiesUniversity of CaliforniaSanta Cruz, CA 95064

Dr. Thomas A. LumpkinDepartment of Agronomy and SoilWashington State UniversityPullman, WA 99164-6420

Other Participants

Mr. Tony BabbDAAIDAU.S. Agency for International Development

Dr. Hugh BollingerNative Plants, Inc.University Research Park

Mr. Douglas W. ButchartAFR/DRU.S. Agency for International Development

Dr. Mary ClutterNational Science Foundation

Mr. Stan DundonOffice of Rep. George BrownU.S. House of Representatives

Dr. Lloyd FrederickU.S. Agency for International Development

Ms. Margaret GoodmanForeign Affairs CommitteeU.S. House of Representatives

Mr. George IngramForeign Affairs CommitteeU.S. House of Representatives

Dr. Howard MinnersU.S. Agency for International Development

Mr. Donald MitchellOffice of Personnel Management

Mr. Stephen D. NelsonForeign Affairs CommitteeU.S. House of Representative

Ms. Julia NicklesLegislative AssistantState of California

Dr. Palmer RogersOffice of Basic Energy SciencesU.S. Department of Energy

Dr. Charles SimkinsU.S. Agency for International Development

Mr. Skip StilesLegislative AssistantOffice of Rep. George Brown

Dr. James WalkerU.S. Agency for International Development

Mr. Henry WilliamsCongressional FellowOffice of Sen. Mathias

OTA Staff

Dr. John H. GibbonsDirector

Dr. Joyce LashofAssistant Director

Dr. Walter E. ParhamProgram Manger

Mr. Bruce RossProject Director

Ms. Barbara LauscheNatural Resources Lawyer

Dr. Betty WilliamsNutrition Project Director

34

Ms. Chris Elfring Dr. Omer KellyCongressional Fellow Consultant

Ms. Judith Randal Dr. Michael PhillipsCongressional Fellow Project Director

Chapter III

Underexploited Plantand Animal Resources for

Developing Country Agriculture

Noel VietmeyerNational Academy of Sciences

Washington, DC 20418

Contents

Page

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ... ..$. .sO.., .O...m

Poor People’s Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Winged Bean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Amaranths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Conclusion . . . . . . . . . . . . ....0.... . . . . . . . . . . . . . . . . . . . . . . 0 $ . . . . . . . . . . . . . .

Tree Legumes: Shock Troops for the War on Deforestation . . . . . . . . . . . . . . . . . . . . .Leucaena . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., . . . . .Calliandra Calothyruas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Conclusion . . . . . . . . . . . . . . . . . . . . . ..+...... . . . . . . . . . . . . . . . . . . . . .......+.

Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Toads, Snails, and Guinea Pigs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Crocodiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Butterflies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Fuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .The Gasoline Plants. ......., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Diesel Fuel You Grow on the Farm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Conclusion. . . .. .. .. .. ... ... ... .$... . 4 . . . . . . . . . . . . . . . . . . 4 . . . . . . . . . . . . . . . . .

373737383939394041414242434445454647

and

Chapter III

Underexploited PlantAnimal Resources for

Developing Country Agriculture

INTRODUCTION

The 1940s was the decade of wonder chem-icals. The miraculous properties of DDT, sulfadrugs, herbicides, nylon, and plastics blindedus to the potentials of nature. Laboratorieswere limitless, nature seemed limited. Man-made was modern, nature seemed passe. Sub-sequent decades seemed to confirm the eu-phoric view; we gave up seeking our new prod-uct needs in the kingdom of nature, theprevious wellspring for civilization’s advances.

As a result, as we move toward the 21st cen-tury, we rely on fewer and fewer plants andanimals. We ignore, or have forgotten, thou-sands of useful species that could broaden andbalance our fount of resources. All this, in faceof the recognition that within a few short dec-ades the petrochemical explosion that beganin the 1940s will be snuffed out.

However, a big change is now occurring inthe scientific community. Researchers arereturning to nature’s storehouse to take stockof its genetic possibilities; to scrutinize speciesthat could make useful new crops and domes-

tic animals. Some of them are species that arewild and untested, some even poorly identified.Though they work largely out of the public eye,these dedicated researchers are quietly ger-minating ideas and laying roots that will growwith and shape our future. Some natural prod-ucts now virtually unknown are likely to be-come mainstays of world agriculture.

Decisionmakers, entrepreneurs, and the gen-eral public should pay more attention to theseresearchers’ results. A groundswell of supportfor the development of new species could leadto a cornucopia of new foods, fuels, and indus-trial feedstocks. It may help extend productiveagriculture to vast regions that today are notarable. It may help raise from despair the everincreasing numbers of humans in developingcountries who waste their lives away in mal-nourished poverty. It may show how to cul-tivate crops that produce raw materials thatnow come from petroleum. It’s a challenge. Butsome of the future’s best resources are out therewaiting in nature.

PLANTS

Botanists and ethnobotanists can reel off long Poor People's Plantslists of obscure plants that seem to warrant rec-ognition. Respondents to recent questionnaires A friend recently told me that he had dis-sent out by the National Academy of Sciences cussed the winged bean with an influentialnamed over 2,000 plant species that deserve Filipino family. “They were incredulous thatmuch greater recognition. Almost none have such a miraculous plant could exist, ” he said.been given agronomic attention. A few strik- “SO, on a hunch, I took them out back to theing examples are given below. servant’s quarters. There, climbing along a

37

38

fence, was a winged bean plant laden withpods.”

“ ‘But that’s just sequidillas,’ they said, dis-appointment echoing in their voices. ‘It’s onlya poor man’s crop!’ “

It is a universal phenomenon that certainplants are stigmatized by their humble associa-tions. Scores of highly promising crop plantsaround the world receive no research funding,no recognition from the agricultural commu-nity; they are ostracized as “poor man’s crops. ”

For information on a poor people’s crop onehas to turn, more often than not, to botanistsand anthropologists; only they will have takenan interest in the plant. Often there has beenno agricultural research on it at all—no vari-eties collected or compared, no germination orspacing trials, no yield determinations or evennutritional analyses. And yet the crop actuallymay be crucial to the lifestyle—even the sur-vival—of millions of people.

Just 50 years ago, the soybean itself was apoor people’s crop. In the United States, it wasspurned by researchers for more than a cen-tury after Benjamin Franklin first introducedseeds from the Jardin des Plantes in Paris. Tobe a soybean advocate then was to risk beingconsidered a crackpot. Early in this century,Americans still considered the soybean a sec-ond-rate crop fit only for export to “poor peo-ple” in the Far East. But then, in the 1920s,University of Illinois researchers establisheda comprehensive soybean research programthat helped sweep aside this discrimination.The soybean acquired new status as a “legiti-mate” research target, and its developmentgained so much momentum that it is now theworld’s premier protein crop.

Nowhere is the neglect of poor people’s cropsgreater than in the Tropics—the very areawhere food is most desperately needed. Thewealth and variety of tropical plant species isstaggering. Some of the Third World’s bestcrops are waiting in the poor people’s gardens,virtually ignored by science. Merely to havesurvived as useful crops, suggests that theplants are inherently superior. Moreover, they

are already suited to the poor person’s smallplots and mixed farming, as well as to poorsoils, and the diet and way of life of the familyor village. Examples are the winged bean andamaranths.

Winged Bean

Perhaps no other crop offers such a varietyof foods as the winged bean. Yet it, remainsa little-known, poor person’s crop, used exten-sively only in New Guinea and Southeast Asia.

A bushy pillar of greenery with viny shoots,blue or purple flowers, and heart-shapedleaves, the winged bean resembles a runner-bean plant. It forms succulent green pods, aslong as a man’s forearm in some varieties. Thepods, oblong in cross-section, are green, pur-ple, or red and have four flanges or “wings”along the edges. When picked young, the greenpods are a chewy and slightly sweet vegetable.Raw or boiled briefly, they make a crisp andsnappy delicacy. Pods are produced over sev-eral months and a crop can be collected everytwo days, providing a continuous supply offresh green vegetables.

If left on the vine the pods harden, but thepea-like seeds inside swell and ripen. Whenmature, the seeds are brown, black, or mottled.In composition they are essentially identicalto soybeans, containing 34 to 42 percent pro-tein and 17 to 20 percent of a polyunsaturatedoil. The protein is high in the nutritionally crit-ical amino acid lysine.

In addition to the pods and seeds, the wingedbean’s leaves and shoots make good spinach-like potherbs. Its flowers, when cooked, are adelicacy with a texture and taste reminiscentof mushrooms.

But perhaps the most startling feature of theplant is that, below ground, it produces fleshy,edible tuberous roots. These are firm, fiberless,ivory-white inside and have a delicious anddelicate nutty flavor. The winged bean is there-fore something like a combination of soybeanand potato plants. And winged bean tubers areuniquely rich in protein—some contain morethan four times the protein of potato.

39

When heated, amaranth grains burst and

Amaranths—major grain crops in the tropi-cal highlands of the Americas at the time ofthe Spanish Conquest, They were staples ofboth Aztec and Inca. But the conquistadorsbanned the cultivation of amaranths becausethe grain was a vital part of native religion andculture. With this political move the Spanishstruck a blow for their church but they alsocrushed the crop. For 500 years little has beendone to study or promote it,

Amaranths belong to a small group of plants,termed C4, whose photosynthesis is exception-ally efficient, The sunlight they capture is usedmore effectively than in most plants and ama-ranths grow fast. Vigorous and tough, ama-ranths have been termed self-reliant plants thatrequire very little of a gardener. They germi-nate and adapt well to the rural farmer’s smallplots and mixed cropping, Furthermore, theyare relatively easy to harvest by hand and tocook.

Amaranths are annuals that reach six feet inheight and have large leaves tinged withmagenta. They are cereal-like plants produc-ing full, fat, seed heads, reminiscent of sor-ghum. The seeds are small but occur in prodi-gious quantities. Their carbohydrate contentis comparable to that of the true cereals, butin protein and fat amaranths are superior tothe cereals.

taste like popcorn. In many regions, however,the grains are more often parched and milled.Amaranth flour is high in gluten and has ex-cellent baking qualities; bread made from itrises and has a delicate nutty flavor,

Recently, W. J. S. Downton, an Australianresearcher, has found that the grain of at leastone amaranth (Amaranths caudatus var.edulis) is rich in protein and exceptionally richin lysine, one of the critical amino acids usu-ally deficient in plant protein. Indeed, theamount of lysine exceeds that found in milkor in the high-lysine corn now under devel-opment.

Conclusion

It is very hard to get grants for research onpoor person’s plants. Funding agencies resist;the plants are unknown to most of them, andthe literature to support any claims may besparse.

Nonetheless, it is now time for agriculturalresearch facilities throughout the world to in-corporate poor person’s crops into their re-search efforts. Third World agricultural devel-opment needs this balance, for only when hisown crops are improved will the poor man beable to feed his family adequately. In futuredecades it may be–as in the case of the soy-bean—that today’s poor person’s plants will befeeding the world,

TREE LEGUMES: SHOCK TROOPS FOR THE WAR ON DEFORESTATION

Man has deforested one-third of SouthAmerica’s native forests, one-half of Africa’s,and two-thirds of Southeast Asia’s, It is criti-cally urgent that the remaining forest cover beprotected from indiscriminate harvest and thatmany now-deforested regions be reforested. A“thin green line” of fast-growing leguminoustrees may be either our last line of defense orour first line of attack.

To most people legumes are limited to thedining table, but to plant scientists legumes in-clude not only vegetables but shrubs, vines, and

thousands of tree species, most of them in-digenous to the Tropics. Actually, the familyLeguminosae is the third largest in the plantkingdom. But out of the 18,000 different spe-cies of legumes, farmers extensively cultivateonly about 20 species including peas, beans,soybeans, peanuts, clover, alfalfa, and even lic-orice. Foresters cultivate almost none.

The potential of tree legumes as useful plan-tation species remains largely unrecognized,yet they offer a particularly promising area forexploration in these days of devastating defor-

40

estation. Indeed, they seem to have special at-tributes that could put them in the front linesof the battle to reclothe the scarred hillsidesthroughout the Tropics.

Legumes, for example, are nature’s pioneersin plant succession. They are among the firstplants to colonize bare land. It therefore seemsecologically wise for man to deliberately ex-ploit them for the same purpose: to quicklyrevegetate eroding or weed-smothered terrain,to halt erosion, and to provide protectiveground cover under which slow-growing,climax-forest species can regenerate. Further-more, many wood requirements might be metby these quick-growing small trees and theycould help spare the last remnants of the nat-ural forests.

Many woody legumes have a hardy, irre-pressible character, suited to a wide range ofsoils, climates, altitudes, and environments.Like other pioneer species, they have a preco-cious nature and grow quickly in an attemptto overtop and preempt the space of their plantcompetitors.

Because of this innate competitiveness, manytree legumes are easy to establish and cultivate.Some can be direct-seeded (avoiding the ex-pense of nurseries and transplanting fragileseedlings), and in some tests even sprayingtheir seed out of aircraft has proven a suitableway to establish plantations. Many occur nat-urally in dense, pure stands, suggesting thatthey probably can be grown in monoculturewithout being decimated by pests.

A most important feature of many legumespecies is that nodules on their roots containbacteria, which chemically convert nitrogengas from the air into soluble compounds thatthe plant can absorb and use. Thus, for aver-age growth these species require little or no ad-ditional nitrogenous fertilizer. Some producesuch a surfeit of nitrogen—largely in the formof protein in their foliage—that they make ex-cellent forage crops and the soil around thembecomes nitrogen rich through the decay offallen foliage.

To give an idea of the potential of this classof trees, three species of fast-growing legumesare mentioned below. Not one of these treesis widely exploited so far.

Loucaena

In the 1960s, University of Hawaii professorJames Brewbaker found in the hinterland ofMexico certain varieties of Leucaena leuco-cephala that grow into tall trees. This was un-expected because the plant was previouslyknown only as a weedy bush. In tropical cli-mates, Brewbaker’s varieties have grown so talland fast that they can be twice the height ofa man in just six months; as high as a three-story building in two years; and as tall as a six-story building with a trunk cross-section aslarge as a frying pan in only six or eight years.

In the Philippines, one hectare of these tallleucaenas has annually produced over 10 timesthe amount of wood per acre that a well-man-aged pine plantation produces in the UnitedStates. Even among the world’s champion fast-growing trees, this is exceptional.

Leucaena wood is thin barked and light col-ored. For such a fast-growing species, it isremarkably dense (comparable to oak, ash, orbirch), strong, and attractive. Its fiber is accept-able for paper-making and the wood can bepulped satisfactorily and in high yield.

But leucaena, a multipurpose plant par ex-cellence, also has other uses. It can supply for-age, for example, and researchers in Hawaiiand tropical Australia have found that cattlefeeding on leucaena foliage may show weightgains comparable to those of cattle feeding onthe best pastures. Leucaena wood also makesexcellent firewood and charcoal. Further, theplant is a living fertilizer factory for if itsnitrogen-rich foliage is harvested and placedaround nearby crops they can respond withyield increased approaching those effected bycommercial fertilizer.

Although arboreal leucaena varieties havebeen cultivated for only a decade or so, they

41

are already being planted over tens of thou-sands of hectares in the Philippines. The WorIdBank has funded one large program, BatangasProvince has a nursery producing 10,000 leu-caena seedlings daily. The province’s dynamicgovernor, Antonio E. Leviste, has decreed thatother nurseries be set up throughout his prov-ince: in churchyards, cemeteries, school-grounds, roadsides—any idle ground. No gov-ernment employee gets a paycheck until he hasset up a leucaena plantation with at least 20trees to produce seed, The consequent green-ing of Batangas has made citizens keenly ap-preciative of deforestation’s ugliness and prob-lems, as well as reforestation’s rewards. Treeplanting now interests the Batangas publicintensely—not entirely for the sake of revegetat-ing eroding watersheds, but for the income andbenefits from exploiting leucaena forage, fuel-wood, and “green manure. ” That the programhas been adopted with gusto by the citizenrydemonstrates the relevance of tree legumes totropical problems as a sort of “appropriateforestry. ”

In more remote southern islands of thePhilippines, Ieucaena (Filipinos call it ipil-ipil)is being planted over huge areas of formergreen-deserts, wastelands lost to coarse, sharp-edged “cutting-grasses,” With its vigor and per-sistence, leucaena—if given a little care—canovertop the grasses, shading them out of ex-istence, and converting waste ground to pro-ductive forest. It is essentially a permanentforest because after felling, the stump of a leu-caena tree regrows with such vigor that theplant is said to literally “defy the woodcutter. ”

Calliandra Calothyruas

In 1936, horticulturists transported seed ofthis small Central American tree to Indonesia.They were interested in it as an ornamental,for like other Calliandra species, it has flowersthat are gorgeous crimson powder-puffs, glow-ing in the sunlight like red fireballs. But Indo-nesians instead took up Calliandra calothyrusas a firewood crop. Indeed, for 15 years stead-ily expanding fuelwood plantations of it havebeen established until they now cover over75,000 acres in Java.

This small tree—barely taller than a bush—grows with almost incredible speed. After justone year it can be harvested. The cut stumpresprouts readily giving new stems that can be10 feet tall within six months. Some trees inIndonesia that are 15 years old have been har-vested 15 times!

Calliandra wood is too small for lumber, butit is dense, burns well, and is ideally sized fordomestic cooking. It is also useful for kilnsmaking bricks, tiles, or lime and for fuelingcopra and tobacco dryers.

Indonesian villagers now cultivate Callian-dra calothyrus widely on their own land, oftenintercropping it with food crops. The plant’svalue is dramatically exemplified by the villageof Toyomarto in East Java. There, land that wasonce grossly denuded and erosion-pocked isnow covered with calliandra forest and is fer-tile once more. Today the villagers actuallyearn more from selling calliandra firewoodthan from their food crops.

Conclusion

These are brief descriptions ofcies of small leguminous trees

only two spe-that have re-

cently proven useful in combating deforesta-tion in Southeast Asia. There are many otherexciting species. In South Korea, foresters in-tercrop bushy Lespedeza species to providefirewood during the early years of the estab-lishment of pine and other forests. In CentralAmerica, there are Enterolobiurn cyclocarpurnand Schizolobium parahyba, in South Amer-ica, Mimosa scabrella (M. bracatinga),Schizolobium amazonicum, Tipuana tipu, andClitoria racemosa; and in the Pacific Islands,Albizia minahassae and Arch idendronoblongum. In Africa, several fast-growingAlbizia (A. adianthifolia, and A. zygia, for ex-ample) are indigenous, and two legume treesintroduced from India, Acrocarpus frax-inifolius and Dalbergia sissoo, have shown ex-ceptional growth rates on appropriate sites. InAsia, there are also Acacia auriculiformis andSesbonia grandiflora.

In foresters’ terms many of these specieshave “poor form,” Their trunks may be too nar-

42

row or too crooked for construction timber or ●

veneer. But, these are species for “peoples’ for-estry.” Their role is for:

●

●

●

farms, backyards, pasture lands, roadsides,canal banks and fencelines;village woodlots and energy plantations tofuel kilns, electricity generators, cooking

●

stoves, and crop dryers;agrisilviculture (agroforestry), because

●

they provide a wealth of products includ- -

ing forage, green manure, and food;

use in shifting cultivation, because the nat-ural drop of protein-rich leaves, pods, andtwigs contributes nitrogen organic matterand minerals to upper soil layers and canmarkedly speed up the rebuilding of wornout soils;quick-rotation cash crops, both for the pri-vate landowner and the government for-est department; andutility purposes such as beautification,shade, and - shelter belts.

A N I M A L S

When early farmers discovered that animalscould be tamed and managed, they eagerly ex-perimented with many of the species surround-ing them. In Asia and the Americas, the silk-worm, yak, camel, water buffalo, llama, alpaca,and guinea pig were selected. Egyptian tombpaintings at Saqqara painted in 2500 B.C. showaddax, ibex, oryx, and gazelle wearing collarsand obviously domesticated. Ancient Egyp-tians apparently domesticated hyenas and ba-boons, as well.

But then the process essentially stopped.Today’s farmers raise the same animals theirNeolithic forebears were familiar with morethan 10,000 years ago. (One exception is therabbit, which French monks tamed betweenthe 6th and 10th centuries because the Churchconsidered newborn rabbits to be fish and theycould be eaten when the Church calendardemanded abstinence from meat.) Althoughthe world’s menagerie contains some 4,000 spe-cies of mammals alone, only a mere six domes-tic animals produce virtually all of the world’smeat and milk.

As agricultural man spread himself about theglobe, he dragged with him this handful of spe-cies. He carried them beyond their naturalboundaries, forced them upon strange andoften fragile environments—usually driving outthe native species that previously predom-inated there, and often drastically changed theenvironments to accommodate them.

Very little meat is eaten in developing coun-tries and because most of them are in the Trop-ics, it is not possible to change that much withcattle, sheep, and pigs. These animals have anevolutionary adaptation to the temperate envi-ronments from which they originated and arelimited in their ability to adapt to new ones.But the world’s fauna is a rich genetic bank thatmay be tapped to increase world food produc-tion. Some of the potential species are unex-pected ones, as highlighted below.

Toads, Snails, and Guinea Pigs

In rural areas of developing countries, it isimportant to produce small animals. They fitbetter into village life and they can be eatenat one meal, so the lack of refrigeration is nohindrance. In Chile, there’s a shiny, olive greentoad (Calyptocephalella caudiverbera). It is agiant toad that can weigh three pounds ormore. Its meat tastes like a cross between lob-ster and chicken. It grows to be a foot long ormore and lacks the toxic skin glands and wartyappearance of other toads. Because of its su-perb and enigmatic taste, the wild toad has longbeen a delicacy of Chilean gourmets. But now,researchers at the La Serena campus of theUniversity of Chile are learning how to farmthem.

In 1975, the University’s Institute of FoodTechnology started farms large enough to pro-

43

duce 100,000 of the choice toadsyears. The intensive methods theyhave made it feasible to supply 10of scallop-sized toad legs each yearstores, restaurants, and canneries.

every twodevelopedto 15 tonsto grocery

The Institute also has dug production pondsout of otherwise useless swampland. The eggs,larvae, tadpoles and adults are all kept apartbecause the voracious toads have no hesita-tions about cannibalism. Normally, however,they feed on small fish, crabs, crawfish, andaquatic plants. The ponds are surrounded withflowers and shrubs to attract insects and boxesof rotten fruit are placed nearby to draw fruitflies to the area. With their long sticky tongues,the toads eagerly capture the insects, Otherthan this, the toads reportedly are given littleattention and in two years they reach marketsize: about 7 inches long and weighing one-halfpound.

Researchers are ecstatic over the ease andcheapness of toad farming, and they are look-ing toward the lucrative international frog meatmarket to export the tender, white drumsticksof these unique Chilean toads.

In Nigeria, the Institute of Oil Palm Researchis developing another potentially valuable newresource : the g ian t Af r i can Land sna i l(Achatina species). This snail grows rapidlyand may weigh up to half a pound. It is eatenwidely in West Africa and is immensely popu-lar in parts of Nigeria and Ghana. The meathas as much protein as beef, but it has consider-ably more of the important amino acids, lysine,and arginine, than even eggs contain. The In-stitute has found the snails suitable for “farm-ing” in shaded enclosures under the trees inrubber, cocoa, or oil-palm plantations. Withproper proportions of males and females, it hasproduced as much as 150 pounds of snail meatin the small enclosures each year,

In Peru, scientists are looking to their in-digenous fauna too. One of Peru’s serious andpermanent problems is a lack of beef. Two-thirds of the steaks of which Peruvians are sofond are imported despite the nation’s chronicdollar shortage. The situation became so seri-ous that five years ago the military junta put

a ban on beef consumption 15 days in everymonth. Chicken production was once believedto be the answer to the problem, but althoughit has grown fast, so has the population. Bighopes were placed on fish, too, but the coun-try lacks the financial resources to install thefacilities needed for national marketing. Theguinea pig is now believed to be the bestanswer so far to the problem posed by the shortsupply of animal proteins.

Guinea pig is a traditional staple. Althoughdomesticated in the time of the Inca, it has notpreviously attracted much research attention.Yet guinea pig is widely consumed in Peru. Thenutritional value of its meat compares favor-ably with that of other meats. The animals canbe raised in urban areas and in villages, wherelarger animals are scarce or impossible to keep.The fast growth and rapid reproduction makesthe guinea pig a sensible resource in the Peru-vian environment, Added to this is the fact thatguinea pigs can live off vegetation that is ofinadequate nutritive value for feeding otherlivestock.

These resources are strange—even repug-nant—to the majority of specialists working toincrease food production and improve humannutrition in developing countries. But to thelocal inhabitants they are traditional foods thatare much sought and enjoyed.

Crocodiles

In Africa, South and Southeast Asia, Aus-tralia, and South America, the populations ofcrocodiles, alligators, and caimans are fastheaded for extinction. In Papua New Guinea(P. N. G.) in the 1960s, the two native crocodilespecies were headed the same way. But nottoday. In the last five years, a remarkably inno-vative project in this, one of the newest andmost underdeveloped nations, has caused adramatic turnaround in the crocodile’s dras-tic decline there. Though the P.N.G. story hasnot been told widely, it is one with immenseimplications for the survival of crocodilianselsewhere. It is also a demonstration of howresources can be managed to conserve a spe-cies, to minimize impact on a fragile environ-

44

ment, and to provide wealth in remote villagesin a developing country.

The P,N.G. program is based on an appreci-ation for crocodile biology. Each year, a femalemay lay between 30 and 70 eggs. Althoughmost of them hatch, predators so relish the ten-der and remarkably vulnerable young hatch-lings that almost none survived the 15 yearsneeded to reach breeding size. In nature, then,there can at any time be found a plethora oftiny crocodiles, but a paucity of breeders. Com-mercial hunting worsens the imbalance be-cause hunters always seek the biggest speci-mens, regardless of the resulting damage to thebreeding populations.

Recognizing that a ban on hunting would belargely unenforceable in remote areas (andgrossly unpopular where man-eaters some-times occur), the P.N.G. Government decidedin 1970 to restructure the trade so that shoot-ing breeders would lose its attraction and theprofit would come from exploiting the hordesof tiny hatchlings that would result. This wasdone through a law banning the sale of largeskins, supplemented by a stiff tariff on smallskins.

Today, villagers in the steamy swamps ofP.N.G. have tens of thousands of tiny croco-diles in their care. They raise them for a yearor two and can sell them for up to $100 each.Crocodile farming has already become themain cash earner for the people there. I per-sonally met a village leader in Wewak who hadcome to oversee shipment of $14,000 worth ofskins headed to New York by airfreight.

The P.N.G. crocodile project is characterizedby:

● Good Science: Despite popular “man-eater” impression, crocodiles live mainlyon fish, though the researchers in P.N.G.have found that young ones also grow wellon frogs, snails, and beetles. The feedingefficiency is astounding: One and one-halfpounds of food gives one pound of weightgain, and foot-long animals can grow to befive and six feet long in less than two years.(Conventional domestic livestock require

●

●

●

●

five to eight pounds of food to produce onepound of weight gain.) Crocodile farmingis also space efficient: dozens of animalsare raised in an area the size of a house-hold living room; in a swamp or jungle,that’s important.Good Conservation: Because the programis based on harvesting young hatchlingsfrom the wild, the economic value of thewild populations and their habitats be-comes forcefully apparent. The program’sfuture depends on them. It gives economicvalue to wildlife protection. Out of pureself-interest, the people become guardiansand conserves of habitats and wildlife. Ina sense, the farming project is just a toolfor conserving the species in its own wildhabitat.Good Sociology: The villagers have a so-phisticated knowledge of the crocodile; theanimal is part of their culture and heritage.They don’t have to be taught how or whereto catch crocodiles, and they take quicklyto the program. Introducing cattle or West-ern-style crop-raising would require mas-sive and tedious education and training.Good Environmental Management: Theprogram is based on living with the exist-ing landscape and resources. It requiresnone of the bush-clearing fencing, forage-grass planting, or pesticide spraying thatrearing other domestic animals would de-mand. That’s important in a fragile tropi-cal rainforest ecosystem.Good Economic Development: What otheragricultural product could give a $14,000income in a remote jungle village?

Butterflies

In remote jungle towns in the north of PapuaNew Guinea are operating butterfly farms—some of the most unusual farms in the world.Around the edge of a field, flowering shrubsare planted to attract the adult butterflieswhose mouthparts are adapted for drinkingnectar from flowers. These butterfly “forages”include hibiscus, flame-of-the-forest, and thestrange, pipe-like aristolochia. Within half-acrecirclets of these flowers are planted leafy plants

45

that the caterpillars feed on. The combinationprovides a complete habitat where butterfliesfind everything they need for their life cycle.Thus few leave, and the farmer retains his live-stock without fencing or walls.

Butterflies may seem exotic livestock to us,but even in the remotest P.N.G. jungle, a vil-lager knows and understands their habits, loca-tion, and lifestyle. And butterflies don’t requirebank loans, veterinary services, artificial in-semination, or the other impediments of con-ventional livestock. Also, when farming in-sects, the villager can work when and if hewants to: there are no deadlines, No hard la-bor and no danger, either. To a Papua Guin-ean, the strange thing is that people are will-ing to pay for a butterfly.

And pay well they do. Ounce for ounce, ex-otic butterflies are far more valuable than cat-tle. And worldwide demand for butterflies isrising. Millions are caught each year and soldto museums, entomologists, private collectors,and perhaps most of all, to ordinary citizens.The fragile, iridescent creatures, mounted in

plastic, decorate purses, trays, tabletops,screens, and other ornamental objects.

With their butterfly farms many rural PapuaNew Guineans are for the first time participat-ing in a cash economy and butterflies are be-ginning to improve the welfare of many villages.At Bulolo, the government has established aninsect-buying agency to help the butterflyfarmers of Papua New Guinea. It purchases in-sects from farmers and fills specific orders re-quested by overseas buyers. Profits go to thevillager.

Perhaps the most striking feature of the pro-gram is that it is actually conserving, and evenincreasing, the numbers of butterflies. Basi-cally, it is an exciting, pioneering conservationproject because it develops a tremendous eco-nomic incentive to preserve populations andhabitats–the program relies on healthy wildpopulations to keep the farms stocked.

Because of this, conservation organizationsare becoming excited by the program, seeingin it a model that could be duplicated to helpsave endangered exotic butterflies everywhere.

The fuels paradise of recent decades hasblinded us to the possibilities of alternativeenergies, especially those for powering ve-hicles. The internal combustion engine, how-ever, remains the most immediately practicalprime mover for motor transport. Finding alter-native energy sources for it poses one of themost severe problems facing the world. Theworld is not so much running out of energy asit is running out of liquid and gaseous fuels.Living plants that produce liquid fuels wouldindeed be boons for the future. Farmers wouldbecome energy producers. Today this is al-ready a distantly glimpsed possibility. Two ex-amples are given below.

The Gasoline Plants

Near Irvine in southern California can befound a field of what is perhaps the most

revolutionary and little-explored developmentin modern agriculture. The crop is Euphorbialathyris and this field is the first attempt at cul-tivating this wild cactus-like shrub. It is thebrainchild of Melvin Calvin, professor ofchemistry at the University of California atBerkeley. Euphorbia lathyris and related spe-cies produce a milky latex, one-third of whichis composed of hydrocarbons—compoundssimilar to those found in crude petroleum oil.Although there are as yet few hard facts onwhich to base firm projections, Calvin esti-mates that the plants might be capable of eachyear producing 10 to 50 barrels of oil per acre.

The hydrocarbon in Euphorbia lathyris andsimilar species is principally polyisoprene, thesame molecule that makes up rubber in the rub-ber tree. But in Euphorbia, it is liquid ratherthan solid. This is because it is a smaller mol-

46

ecule, but Calvin points out that its hydrocar-bon molecules are similar in size to those foundin crude oil. He thinks that Euphorbia typehydrocarbons might even be processed intofuels and petrochemicals in exist ing oilrefineries.

A distinguished scientist, Calvin received the1961 Nobel Prize for Chemistry in recognitionof his achievements in unraveling the chemi-cal processes of photosynthesis. Growing pe-troleum plants is a new venture for him, butalready he projects that this country’s vast pe-troleum demands could be met by plantationscovering an area the size of the State ofArizona. He calculates the costs of harvestingpetroleum from trees to be competitive withcurrent oil prices: a total of between $5 and $15per barrel for growing and processing theplants.

A plantation of such plants should be eco-nomic in dry lands unsuitable for growingfood, Though little is known of their require-ments or yields, Euphorbia species are hardyand need little or no irrigation and care. Calvinforesees that the plants will be mowed near theground and the harvested plants crushed to re-lease latex in much the same fashion as is donewith sugar cane. The stumps quickly resproutnew stems so that replanting would be unnec-essary.

This is truly a pioneering concept, and thefield near Irvine is the first small step in evalu-ating its practicality. Already, larger planta-tions are planned. The University of Arizonahas a million-dollar grant from the DiamondShamrock Corporation to develop Euphorbialathyris into a crop; the Government of Kenyais investing (perhaps unwisely) $10 million inplantations. If such projects are successful, thisobscure wild plant will enable the world’s des-ert countries to have oil fields on top of theground.

Diesel Fuel You Grow on the Farm

Ohio State University (OSU) in Columbus,Ohio, transports students around its spread-outcampus using a fleet of buses. Nothing unusual

in that. But, this year (1980) OSU is using soy-bean oil as fuel.

Over the past decade, various student proj-ects at the OSU engineering school have shownthat vegetable oils can be used as fuel for dieselengines. For a full year the university has runa large, 60-passenger bus partly on soybean oil.The experiment proved so successful that inSeptember the whole university fleet wasswitched to the new fuel.

The soybean oil is collected from deep-fatfryers in cafeterias and kitchens across theUniversity, filtered through muslin cloth by theengineering students to remove gunk andsolids, and blended into diesel fuel. A ratio ofone part soybean oil to four parts diesel wassettled on as it gave a stable mixture, lowestfuel consumption, and actually smoked lessthan diesel fuel alone.

The first bus maintained its normal 40 houra week schedule. After 4,5oo miles on the soy-diesel blend the engine was taken apart and in-spected. Little or no abnormal wear had oc-curred. The engine was actually in such fineshape that it was merely reassembled andreturned to service without further attention.

Although it is little-known to the general pop-ulace that diesel engines can be run on vege-table oils, this knowledge is not new. In the1890s, Rudolf Diesel concluded that any ma-terial that was injectable and would ignite atthe temperatures generated by compressing aircould serve as fuel for his engine.

During World War II this knowledge was putto use. When Japan was cut off from petroleumsupplies, the 65,000 ton Yamoto, the largest andmost powerful battleship of its time, used edi-ble, refined soybean oil as bunker fuel. Japa-nese forces occupying the Philippines andAllied troops trapped in northern Burma usedcoconut oil for fueling diesel trucks andgenerators.

Since then, that experience has been largelyforgotten. But in the U. S., South Africa, Aus-tralia, Brazil, Canada, Thailand, Japan, andperhaps elsewhere, individual researchers arerediscovering that diesel tractors, buses, and

47

stationary engines can operate when fueledwith sunflower, soybean, peanut, rapeseed,and other vegetable oils.

The experiences are usually solitary andmost involve only very short running times.The practical potential of vegetable oils as com-mercial diesel fuel substitutes is therefore un-certain. But, at least in the short run, they work.

Of all the research laboratories testing dieselengines fueled by vegetable oils, the South Afri-can government’s Division of Agricultural En-gineering has the most experience. At its lab-oratory near Johannesburg it is running 10tractors on sunflower oil. Fiat, InternationalHarvester, John Deere, Landini, Massey Fer-guson, and Ford tractors are being used, Withtwo exceptions the tractors started satis-factorily on undiluted sunflower oil, All oper-ated normally, delivered almost full power, andhad virtually the same fuel consumption as ondiesel fuel. A Ford 7000 tractor has run trouble-free for almost 1,400 hours of operation on afarm using a blend of 20 percent sunflower oiland 80 percent diesel fuel. At the end of thistime it was found that deposits in the combus-tion chamber, cylinders, and piston ringgrooves were no worse than those formedburning normal operation on diesel fuel. Onthe other hand, carbon deposits on the injec-tor nozzles were worse and contributed to aneventual 4 percent power loss and serious gum-ming of the crankcase oil.

The rapid compression of fuel and air in thecylinder of diesel engines generates enoughheat to ignite the mixture and power the en-gine. Unlike a gasoline engine, no spark is

needed. Injecting the fuel into the combustionchamber is the most crucial step in a diesel en-gine. The fuel must be forced in against thepressure of the compressed air and to make thisdoubly difficult, the fuel has to be in the formof mist. If not atomized, the fuel burns slowlyand unevenly, reducing engine efficiency, rais-ing unburned pollutants in the exhaust and thelubricating system, and even forming depos-its of solid carbon in the engine itself.

Vegetable oils are more viscous and less eas-ily atomized than diesel fuel and are thereforemore difficult to inject successfully. This isprobably why the injector tips suffered build-ups of carbon. Coking and the resulting incom-plete combustion diluted the lubricating oil andgummed it up because vegetable oils will poly-merize when they are hot and next to metal.

The South African engineers, however, havefound a way that seems to avoid these difficul-ties, They slightly modify the sunflower oil inchemical reactions using small amounts ofethanol or methanol. The resulting ethyl ormethyl esters derived from sunflower oilcaused much less coking than diesel fuel itself.Furthermore, they produced much less exhaustsmoke, and the engine ran quieter so that thecharacteristic diesel knock was less audible,And, against all expectations, the engine gavemore power with the new fuel than with dieselfuel. Thus tractors were running on a renew-able fuel grown by farmers and achieving bet-ter results than on diesel fuel, Much yet re-mains to be done to test the widespreadapplicability of these results, but it is a line ofresearch that is bright with promise,

CONCLUSION

Development specialists usually promote re- snails, guinea pigs, and butterflies. Instead theysources and technologies that are familiar to recommend and sponsor the introduction oftheir own lives. Most agronomists, foresters, species that are foreign and unconnected to theanimal scientists, and nutritionists know little lives of those they want to help.about the wealth of plants and animals to befound in the developing world. They all but ig- This paper identifies just a few exciting un-nore the significance poor people’s crops, le- derexploited resources for developing countryguminous trees, and animal resources such as agriculture. Detailed information on them and

48

many others can be found in the following Na-tional Academy of Sciences reports (all ofwhich are available without charge from the ●

Commission on International Relations, JH215, National Academy of Sciences, 2101 Con- ●

stitution Avenue, N. W., Washington, D.C.20418): ●

● The Winged Bean: A High Protein Cropfor the Tropics

●

● Leucaena: Promising Forage and TreeCrop for the Tropics Underexploited Trop-

ical Plants With Promising EconomicValueTropical Legumes: Resources for theFutureGuayule: An Alternative Source of Natu-ral RubberMaking Aquatic Weeds Useful: Some Per-spectives for Developing CountriesFirewood Crops: Bush and Tree Speciesfor Energy Production

-.

Chapter IV

Native Plants: An InnovativeBiological Technology

Cyrus M. McKell, Ph.D.Director of Research

Plant Resources InstituteSalt Lake City, Utah 84108

Contents

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .The Role of Native Plants in Sustaining Food and Forage Production . . . . . . . . . . . . . . . .Where Native Plants Are Being Used Today . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Research Efforts on Native Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .How Do/Could Native Plants Increase or Decrease the Need for Fertilizer,

Pesticides, Irrigation, and Machinery? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Fertilizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Pesticides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Machinery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

What Is the Potential Role of Native Plants to Restore, Improve, or SustainFood Production on Tropical and Subtropical Soils? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

What Research, Development, and Implementation Scenarios Could Help NativePlants Realize Their Potential of Enhancing Tropical Soil Productivity? . . . . . . . . . . . . .

Scenario A.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Scenario B . . . . . .Scenario C . . . . . .

What Changes in AttitCultivators . . . . . .Legislators . . . . . .Financiers . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ude Are Needed? . . . . . . . . . . . . . . . . . . . . . . . . . , , . . . . . , . . . . . . . , ,. . . . . .,0.., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4...

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...!

. . . . . . 4....., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .!

International . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .What Biophysical, Cultural, and Socioeconomic Conditions Would Be

Conducive to Project Implementation?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Biophysical Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Cultural Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Socioeconomic Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

What Are the Major Constraints on Development and Implementation ofNative Plant Use?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Scientific Constraints. . . . . . . . . . . . . . . . ....4...0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Environmental Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Culture Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Economic Constraints ..., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Political Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

How Would Implementation of a Native Plant Technology Affect theNeed for Capital? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

What Would Be the Impact of Wide-Scale Implementation ofNative Plant Use on Socioeconomic Structure? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table

5151525356

5858

.595960

60

616161616262626262

62636363

636364646464

65

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Table No. Page

1. Little Used But Potentially Useful Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Chapter IV

Native Plants: An InnovativeBiological Technology

ABSTRACT

The concept of native plants reflects a newdirection in botanical development. The termimplies the idea that rather than adapting theenvironment to the plant, an indigenous plantexpresses the best adaptation to an environ-ment and improving on this expression willyield various benefits. Bringing marginal landsinto widespread agricultural use often employstechnologies and plant species inappropriateto these situations. This occurs with a total dis-regard for the climatic limitations of the envi-ronments. A new approach is required.

Development of native or indigenous plants,particularly those adapted to tropical and sub-tropical soils, could be beneficial at differenteconomies of scale, In some instances, their de-velopment will be small and amenable to useby individual farmers or farming groups, Onthe other hand, there will be instances wheredevelopment will be large scale and have in-ternational implications.

Native plants can be particularly useful insustaining fertility on depleted or marginalsoils and improving general productivity. Theyuse an “agroecosystem approach” to obtainnecessary production. Polycultural (mixed)cropping systems are especially applicable intropical locations; they rely heavily on the po-tential of adapted or indigenous plants. Nativeplants represent an underused resource andconstitute an opportunity for positive botani-cal developments,

The coordinated, integrated development ofindigenous plants could allow for multiple andadditional benefits greater than the initial goalsof soil fertility, food production, or raw mate-rials, There is an immediate need for inventoriesof existing native crops for their developmentpotential. The world’s tropical and subtropicalgermplasm is poorly known, Throughout theworld, knowledge of plants and their uses byindigenous peoples is disappearing becausefarming systems are being converted to mono-cultural uses. Germplasm storage of potentiallyvaluable varieties and strains requires imme-diate attention. Demonstration of practicalworking models with specific native plantsmust be performed.

One factor limiting the development of nativeor other unconventional plants is an institu-tional bias against them. The major emphasisof plant research during the last 100 years hasbeen directed at the dozen or so primary foodcrops—to the exclusion of almost everythingelse.

To overcome this institutional bias will re-quire innovation in policy, research and devel-opment, and program implementation. Devel-opment of native or adapted plants shouldallow for an integration of these concerns. Thecapabilities of various governmental and non-governmental institutions should be directedtoward the goal of sustaining soil productivityin both the short- and long-term context,

INTRODUCTION

The purpose of this paper is to present a non- nology to improve productivity on soils in trop-technical description and evaluation on the ical/subtropical areas. The paper addresses sev-utility of “native” plants as an innovative tech- eral major questions that appear as subsections,

51

52

The term native plant needs clarification. Allplants may be considered native or indigenousto some location on the earth, but when a plantis taken to an area where it is not naturallyfound, it becomes an introduced species. Thisdistinction is too constraining and can over-look the importance of adaptation—judged ei-ther from actual observation or from scientificevidence of ecological similarity. In this report,native species are those plant species growingin an area that have not been exploited for com-mercial development and export. Some nativespecies may have desirable attributes and a po-tential for intensive use while others maymerely serve to “fill in the spaces” of the plantcommunity and have only minor developmentpotential. This paper is limited to indigenousspecies that have not been extensively de-veloped.

Native plants hold great promise for meetingthe expanding needs of society for food, fiber,fuel, and enhanced land productivity. In thesearch for a plant or plant product to serve amarket or domestic need, plants native to agiven region may already express the range ofadaptation necessary for sustained use. Butthey are often overlooked in favor of an im-ported species. A good example of indigenousplants being overlooked is in rangeland im-

provement programs in the Western UnitedStates where native shrubs were removed inorder to plant introduced grasses (11). Al-though plant exploration and introduction hasbeen emphasized by the economically devel-oped nations, the search for new plantmaterials has been directed along conventionallines and the potential of native species hasbeen overlooked.

In the past, the common procedure has beento examine existing files or materials found inplant introduction stations to find new plantsand plant products rather than to explore lo-cally for possible new products. Because of theincrease in energy costs and the energy com-ponent in existing production activities, a newlook for alternatives is justified. A particularlyattractive opportunity to develop native plantsexist in tropical and subtropical areas. Theseareas generally have not been of interest as asource of plant materials because the devel-oped nations are, to a large extent, located intemperate climates. This has limited germ-plasm collection, research testing, and intro-duction of new crop species. Additionally,most American primary crop species are in-troductions from the Old World, and thesehave been genetically developed over long peri-ods of time for intensive agricultural use.

THE ROLE Of NATIVE PLANTS ON SUSTAININ0FOOD AND FORAGE PRODUCTION

Native plants serve a traditional role in manytropical and subtropical countries. Various in-digenous species have been used for food, fuel,livestock feed, construction, fiber, medicines,and other purposes on a sustained yield basis.The species are either gathered from naturalplant communities (forests, rangelands, marshes,etc.) or harvested from small farmed plotsunder various degrees of cultivation. Culturesas diverse as Mexico, Sri Lanka, and Indone-sia have well-documented histories of wide useof indigenous plants for medicines, foods, andother uses. Most of these native plants have notreached a level of development sufficient to

make them commercially useful. Notable ex-ceptions include rubber, corn, pineapple, andpotatoes. Most species, however, are unspec-tacular in their attributes and find beneficialuse only in the day-to-day existence of the localpeople.

Overuse of native species brought about bypopulation increases and energy shortages iscreating adverse impacts on many species andtheir systems of production. Where previouslya conservative level of plant use generally as-sured their natural replacement and did not re-duce their genetic diversity, exploitation of

53

land resources by overgrazing, intensive agri-cultural development, forest clearing, indus-trial development, and widespread soil degra-dation threatens to eliminate many usefulspecies.

For example, a recent National Academy ofScience assessment of environmental degrada-tion of the groundnut basin of Senegal (12) in-dicates that overuse due to population increaseand cyclic drought has resulted in the disap-pearance of many native species used for fruitand livestock fodder. Theoretically, some ofthese species are still present in the noncul-tivated bush areas. An example is Ziziphusmaritiana, a desirable fodder shrub, that hadessentially been eliminated from areas adjacentto intensively cultivated farmlands by overuse.At a conference in Australia on Genetic Re-sources of the World, concern was expressedthat valuable genotypes and gene combinationswere being lost due to the impacts of humanpopulation expansion. Associated with the di-

rect loss of genetic resources is a substantialreduction in soil fertility and an increase in lessdesirable plants.

Native plants also play an especially impor-tant role in improving crop performance anddiversity. Indigenous or locally cultivatedrelatives of many common crop plants offersignificant potentials for crop improvementprograms within the temperate and tropicallatitudes. Recent discoveries of wild perennialrelatives of corn (Zia mays) could prove ex-tremely important to the future developmentof this crop. Similarly, the expression of ex-panded environmental adaption often inherentin many native plants could allow for muchwider cultivation of the species while reduc-ing artificial inputs. Recent work with salt tol-erance in major grain crops and tomatoes re-lies heavily on the adaptive qualities of variousnative and overlooked indigenous relatives ofthese important crops (13).

WHERE NATIVE PLANTS ARE BEING USED TODAY

Native plants are being used all over theworld, Many species find extensive use in de-veloped agriculture and some native species al-ready enjoy limited commercial use in areasof optimum adaptation (table 1). Opuntia cactusfruits in central Mexico are collected and soldlocally. Fibers are removed from the Leghugeacactus for use in making Mexican mats, shoes,and baskets. Numerous species of native treessuch as Mangosteen (Garcinia mangostana) insoutheast Asia, Naranjilla (Solarium quitoense)in Colombia and Ecuador, pejibaye peach palm(Gudiema gasipaes) in Central America, andsoursop (Annona muricata) of the West Indiesproduce exotic fruits for local markets.

The important point is that the usefulness ofsome species is known only to local people oris generally not appreciated by a wide au-dience. A number of examples of fruit, vege-table, fiber, oil, and forage species are de-scribed by the National Academy of Sciencesin their studies on underexploited plants (18).

Such underdeveloped species may possessunique features that could be useful in new ap-plications or supplement existing crop plantsif they were screened for optimum size, shape,product quality, and adaptability to variousmanagement practices.

The genus A triplex is an example of a groupof semiarid, subtropical plants currently usedbut possessing significant potential for increas-ing rangeland productivity. Various shrubbyA triplex species are valuable as livestock for-age during seasonal dry periods when mostgrasses are below required levels of crude pro-tein for animal nutrition. The protein contentin A triplex is high and balanced. The exploitivesubsistence level grazing practices and exten-sive gathering of A triplex on the rangelands ofSyria, Iraq, and other Middle Eastern nationshas nearly caused the disappearance of thesepalatable shrubs (23). An integrated develop-ment program of collection and revegetationwith this native species and other adapted

54

Table 1 .—Little Used But Potentially Useful Plants

Present Yield

Common useful Potential Present Growing State of Per Hectare Time to First

Name Scientific Name Portion use Areas Cultivation Per rear. Harvest

A. Humid Tropics

Cocoyam carbohydrate,protein

carbohydrate,

oil, protein.“heart of palm”

carbohydrate

Tropical Americas,West Africa

CentraI and Northern

South America

domesticated 30-60 tons

wet weight

domesticated 3 tons

3-10 months

6-8 yearsfruit and

stemPeach

palm orpejibaye

Taro and

tiecssBuriti

Egypt, Philippines,

Hawaii,CaribbeanAmazon Basin.

Veneuela,Guianas

domesticated 22-30 tonswet weight

mostly wild ?

6-18 months

9

tuber

fruitkernel.

Shoots

trunk andleaves

fruit andkernel

fruit andkernel

oil, starch,vitamins A and

C, timber, cork.

fiber, heart of

palm”oil* protein,

fuel

oil. fuel

Babasaat

palmPequi

tree

Orbigrrya martinia

Caryocar bresilienss

Amazon Basin mostly wild 1.5 tons

mostly wild ?

10-15 years

9 yearsAmazon Basin,Central Brazil,Guianas

Amazon BasinSejepalm

winged

Jczzenie polycarpa

~P~ tetwnolobus

Durio Zibcthinus

fruit oil resemblingolive oil

protein, oil.carbohydrate.

livestock feed

carbohydrate,

fat; vitamins,

flavor

highly prized

flavor

large citrusfruit

wild 22 kg/ tree

per yeardomesticated 2.5 tons of

dry beans

?

10 weekspods, beans,tubers,foliage

fruit

Papua New Guinea.southeast Asia.

Sri LankaSoutheast Asia haphazardly ?

cultivated

7 years

Mangosteen

treePummelo

tree

Scuncntree

ckrcinit nsan@stana

Citrus grandis

fruit

fruit

fruit

Southeast Asia

Southeast Asia

domesticated 50 kg/treeper year

domesticated ?

15 years

several years

*Anrrona muricara fruit andjuice

Southern China,Australia, Africa.tropical Africa.

West IndiesWestern Amazon

domesticated 6-10 tons

[ !villa

tree(%aya

bush

Ramscherb

Cauassu

herbLcucacna

Ptmrrmma crrrnpiarfoiw

Cnidwcvlus CIIa,l,anlansa

I%whmcti mwa

Calafhca lutea

Ieucaena Icucocephala

fruit grapelikefruit

vitamin-rich

leafy vegetable

fiber and live-stock feed

commercialwax

livestock feed,timber. fuel.paper, soil

fertilizer, dyestuffs, humanfood. erosionand watershed

control, nurse

tree, fire andwind breaks

wild 7

domesticated ?

3 years

2-3 monthsMexico and

Central AmericaEast and Southeast

Asia. BrazilAmazon Basin.

Central AmericaCentral America.

Mexico. Southeast

Asia. NorthernSouth America.Australia. Hawaii.

East and West Africa,Papua New Guinea,Caribbean. India

stems and

foliageleaves

domesticated 1.4 tons fiber, 2 months

20 tons feedwild 0.8 tons 9 months

of waxdomesticated 12-20 tons less than 1 year

and wild of forage, to more than20-50 tons 3 years,

of wood depends onvarietyplanted

Ieaves,

w o o d , pek.

seeds. bark

8. Scmwld and Arid Tropics and Subtropics

seed. leaveS.

and stems

seed. root

seed. leaves.

and stem

Channel .L”chinochkm [uncmnamdlc!

Buffalo <“ucwhiro focridlssimacourd

Guar C)”amopns tctrapxroloba(clusterbcln I

carbohydrate.

protein. live-

stock feedoil. protein.

starch

Central Australia wild v several monthsafter heavy

rain

most ly 2.5 tons of 2 years

wild seed, 22 tons

starchdomesticated 18-24 tons 3-5 months

green fodder.0.9-2 tons

seed

Mexico. Southwestern

United States

gum, protein,

oil. livestockfeed

United States.

Pakistan, India.Australia. Brazil. ,

South Africa

Table 1 .—Little Used But Potentially Useful Plants—Continued

pfescnt yieldCommon U“)cful PotcntmJ Present Growing Slate of ?CI Hectqr. T i m e 10 k’ust

N a m e Scicntirsc Name Portion Usc Areas C’ultlwation Pet r e a r }14rt CSi

Appk-ting AwCiO albida..—

acacia treeRamon Brosimum alicaurum

tree

Icavei, shoots,pods, Sceda

leaves, twigs.nuts

leave>

leaves and

shoots

stems andleaves

pods and Icave}

seeds

whole p~t

livestock feed,

human protesnlivestock feed,

atbohydrate,protein

Iivcstock feed

Tropicaf and Wikf

Southern AfricaCentraJ America, mo>tly WSIJ

Southern Mexico,

Caribbean islandsAustralia. Isrucl .411d ~n.f

usttivaluiworldwldc in w lid and

warm arid ztinc~ WI IwawdUnited States and Wdd

Mexican dcstrt.s

Atacoma desert 01 cultlv Alcbl

~ik, Canq island>

United States and mostl) wddMexican deserts.Israel

United Scsws. Mcxuxn mostl) udddeserts. Spain. Turkc}

2(MJ kg several years

Scverd years

protein●

cawiJ Ca:sb sfurtilshrub

SaJtbush Atriplcx spp.

i ,’2 um df )Wesght

1-1.5 tonsIivcstock tcul

Gnddiua k“uphorbsa anrrsyphilitsca

shrub

Tumxrugo bosopu tansarugu

treeJOjOtM &nwsondsu chutcnsu

shrub

hard wax .

high protcm.

Jives[ock Iced

Iiquld wax

idcnticd toSperm oiJ

naturaf rubber

I tJ-2tJ SJlccp

2 tons

Guayuk Parthentum argentatum

shruh

It. j j Ion

C Afountaltt kmvronmctm oj”low Lrttrude$

Grws A mamrtthus COUd&ltSiS,

amarJssth etc

high IyUtW.htgh proteus,

starch, VIUUISIJU

Andeao re~wr UI

!bulh Amcrw

seed prolcin.

arbohydratccarbohydrate.

livestock feed

fruit and Iuicc

Andcan rcgicm nfSou[h Amer ica

A n d e a n re:irm O(

S o u t h Americ~

Centraf andNorthern SOIIIIIAmerica

Papua New Gvsinca.

Sosrthcast .4sia.Sri Lanka

donwticztcd *

tlomr~ticxtcd ‘

dwrwttcatcd I-2 tonsof fmil

d~mcsticatcd 2_S tons ofdry bean<

Iubcrs. stcms.

IC8VCS

ftuil

pnds. beans.tuhcrs.foliacc

protein. oil.cxrbohydratc.livestock fcesf

seed carhohydratm.prolcin

tidaf flats andestuaries inaU latitudes.

brackish marshyareas in Thailand

world w-idc. includln~

salty soih and salineirrigation watcm

Atacama desert of

Chifc, Canaty Isfandssescoasts from

AustralL :: 2~A-

Argentina to Baia

Cafifomia

1

domesticated ‘

rnasflv wild I -1.5 tnrl<

frrmt citrus fmit

I?avcs andShonts

hiph profcin,

livestock feed

pods and leaves high protein.

IJvestock feedIlvcstock feed.

sand stabiliza-

tion

cultivated 1 ~20 sheep

mostly wifd ?leaves wrdstems

Spirulina. Spirsdirsa platcnsis

hfuc-green S@irulina maawna*ac

—

mstitc alga poultry feed. Lake Chad, Vafky cultivated 3 tons vvcrd days

of Mcx ico ~rolcin

tein human food

very high pr~

Atriplex species from similar climates couldsubstantially restore rangeland productivity tothis region.

Another example of a native plant that is re-ceiving considerable attention on a pilot-scalelevel is jojoba (Simmondsia chinensis), an ever-green shrub indigenous to the Sonoran desertsof the United States and Mexico. The plant isvalued for the liquid wax contained in its seeds.

RESEARCH EFFORTS

Research on native plants is being conductedby many different groups ranging from privateindividuals and companies to State, national,and international agencies. However, no co-ordinated research effort can be expected be-cause of the diversity of potentially useful na-tive species, the various countries where theyare growing and could be grown, and the risksinvolved in developing new crops for ill-defined markets.

As has probably been the case throughouthistory, plant resources have been developedto meet existing and short-term needs. The dif-ference today is the high cost of bringing newproducts into a highly competitive market. Op-portunities for new products or uses from na-tive plants can occur as a result of changes (orpotential for changes) in consumer preferencesor as existing products come into short supplyand can be replaced by a native plant product.

It is difficult to identify organizations per-forming research on native plants, but they fallinto the following categories:

1 Broad spectrum agencies sponsoring ex-ploration collection and evaluation. Ex-amples:

● USDA: plant introduction, plantmaterials centers (nationwide).

● FAO (Food and Agriculture Organiza-tion of the United States) seed ex-change, international development.

● SIDA (Swedish International Develop-ment Agency): sponsoring projects topreserve genetic resources.

The wax is similar to sperm whale oil and hasa potential for use in many industrial proc-esses. Field test plantings have been made inArizona, California, Israel, Mexico, and Aus-tralia. Because the plant is adapted to areas ofextremely low rainfall (less than 10 inches), itcould become an important cash crop for theappropriate arid areas (10).

ON NATIVE PLANTS

2. Agricultural experiment stations doingwork on individual plant species with lo-cal concern. Examples:

● University of California AgriculturalExperiment station, Riverside: jojobawax.

● University of Hawaii Agricultural Ex-periment Station: Leucaena trees.

3. Private organizations, agricultural enter-prises working to develop products fromvarious species. Examples:

●

●

●

Firestone Rubber Company: guayulefor rubber development.Native Plants, Inc.: developing newtechnology for tissue culture propaga-tion of various plants.Jojoba International, Inc.: encourag-ing commercial plantings of jojoba.

Funding of native plant research is very depen-dent on the species in question. Obviously thepotential for some species is greater than othersdepending on the scarcity and quality of theexpected product, the abundance of the plants,and the needs of society. Currently, there is ahigh interest in native plants with potential assources for biomass energy. Unfortunately,there is little, if any, coordination in researchfunding for native plant development or in theestablishment of priorities. As of 1979, the to-tal U.S. funding for research and developmentof underexploited plants was limited to lessthan $10 million, half devoted to jojoba.

The uncertain path of development for a nat-ural rubber product from the native shrub

57

guayule (Parthenium argentatum) illustratesthe problems of developing a native plant. TheNational Academy of Sciences (13) pointed outthat in 1904 a company was formed to extractrubber from the guayule bush, By 1910 thiscompany was the sixth largest in Mexico butthe wild stands of plants quickly becamedepleted. Expelled from Mexico by PanchoVilla, the company continued limited opera-tions in Salinas, California. Cut off from natu-ral rubber supplies from Southwest Asia in1942, the United States took over the companyand planted over 12,000 hectares of productionand experimental plots of guayule. These fieldswere just coming into production after the warin 1945, but because natural rubber was againplentiful and a fledgling synthetic rubber in-dustry gained the Federal price supports, theguayule fields were destroyed. Recognizing theneed for dependable supply of natural rubber,Congress passed the Native Latex Commercial-ization Act of 1978 which makes $30 millionin Federal funds available for research. Sub-sequently, Firestone Tire and Rubber Companyand Goodyear Tire and Rubber Company haveinitiated field trials of guayule in the South-west. In Mexico, plans are underway for a nat-ural rubber industry using guayule from nativestands and later from established plantations,

Obviously, a more integrated and organizedeffort will be needed to bring the benefits ofother native plants into reality. The researchcommunity and society simply cannot be sub-jected to the vagaries of 70 years when a plantof national value takes so long to be developed.Coordination is needed to stimulate innovationin policy planning, research and developmentfunding, and commercial implementation.

Substantial, integrated programs are neces-sary to bring native plants into commercialproduction. We know that genetic quality ofconventional crops and appropriate culturalpractices have been improved over a longperiod of time. With this history of develop-ment, we can expect that new crops/productsfrom native plants can be developed with evengreater efficiency. Significant breakthroughsmay take place (such as the application of va-rious biotechnologies) but for the most part, re-

search funds, time, and vision will be neededto unlock these new resources.

One of the first research steps must be toidentify promising native plants and describesome of their characteristics. A survey spon-sored by the National Science Foundation (22)described six new crops with a potential fordevelopment in the United States. A thoroughcoverage was given to ten new agriculturalcrops (20) that already have received some at-tention. Goodin and Worthington (8) helpedstimulate interest in native plants with theirconference on Arid Land Plant Resources.

Probably the greatest stimulus to the devel-opment and use of native plants in recent yearshas been the series of bulletins published bythe National Academy of Sciences. Underex-ploited Tropical Plants With Promising Eco-nomic Value. NAS (18) describes 36 tropicaland subtropical plants that have a high poten-tial for use as cereal, root, vegetable, fruit, oil-weed, forage, and fuel. The Winged Bean—AHigh Protein Crop for the Tropics (17) providesinformation on a tropical legume native toSoutheast Asia and New Guinea with a poten-tial for improving human nutrition. Guayule:An Alternate Source of Natural Rubber (14) isa report on the development potential of a sub-tropical desert shrub of Mexico and Southwest-ern United States that produces a latex prod-uct similar to natural rubber from SoutheastAsia. Leucaena: Promising Forage and TreeCrop for the Tropics (15) provides informationon a vigorously growing tree and bushy plantthat produces nutritious forage as well as re-storing soil fertility. Other benefits include tim-ber, fuel, and pulpwood as well as soil conser-vation and stabilization. Tropical Legumes,Resources for the Future (13) reports the find-ings of a group of legume specialists on 200species that warrant research and developmentto achieve their optimum potential. ProductsFrom Jojoba (16) gives a review of the chemis-try of the liquid wax obtained from this shrubnative to Southwestern U.S. deserts.

These publications all highlight the immensepotential existing within the botanical worldto benefit agriculture, forestry, and horticul-

58

ture, particularly in the developing countries. conservation of existing habitats. The rapid dis-These and other surveys consistently document appearance of extensive semiarid, subtropical,the immediate need to inventory indigenous or tropical plant community compounds theknowledge concerning native plants and their problem of collecting, researching, and devel-uses, germplasm collection and storage, and oping these under-exploited plant resources.

How DO/COULD NATIVE PLANTS INCREASE OR DECREASE THE NEEDFOR FERTILIZER, PESTICIDES, IRRIGATION, AND Machinery?

Any change in the present use pattern of fer-tilizer, pesticides, irrigation, and machinerywould depend completely on the nature of thenative plant being developed—whether the par-ticular plant could be developed on an inten-sive or extensive basis, or the degree to whichthe plant is susceptible to insects and diseases.However, any move to increase productivitywould generally require an increase in the levelof inputs. The adaptation of some indigenousplants to multicropping systems or polycul-tures could significantly reduce the need forartificial inputs. The development of such pro-duction systems is just in its infancy, however,and models appropriate to widespread appli-cation are virtually nonexistent.

Some specific examples of inputs requiredby various native plants will illustrate theirvariable nature.

Fertilizer

Three possibilities for fertilizer use may beseen:

1.

2.

3.

Legume species may have minimal fer-tilizer requirements, needing mainly phos-phorus, sulfur, and micronutrients.Some native species may not require highlevels of fertilizer because of their adap-tation to low nutrient environments.Non-1egume species may require substan-tial amounts of fertilizer to achieve optimalproduction levels.

Leguminous native plants are particularly at-tractive because they can serve to increase soilnitrogen as well as provide useful productssuch as fuel, forage, and wood biomass. Fast

growing Leucaena trees have been shown toprovide foliage containing 1,000 to 1,300 lbs.of nitrogen a year and can restore the fertilityof tropical soils depleted of nitrogen and or-ganic matter (15). Felker (15) suggested thatmature tree legume orchards receiving no ir-rigation or nitrogen after establishment may in-crease soil fertility up to four times greater thannon-leguminous tree species. Numerous leg-ume shrubs and trees such as Acacia, Prosop-sis, Desmodium, Cassia, and Stylosanthesenhance soil fertility while at the same timeserving as live fences, crop interplantings, orrange and pasture fodder. Many examples ofsoil fertility increase are presented in Tropi-cal Legumes: Resources for the Future (13),Tropical Pastures (21), and in papers presentedat the International Symposium on Browse inAfrica.

Some native species may not require largeamounts of fertilizer because they are adaptedto soils of medium to low fertility. Under suchconditions, plant growth and production couldbe expected to be correspondingly low. If highyields for commercial production are desired,the level of fertility must be increased accord-ingly. Intensive cropping has been shown todeplete soil fertility and any continuous pro-duction in a new agricultural location wouldeventually require regular soil fertilization.

Non-legume native plants may require largeincrements of fertilizer to produce at levelssufficient to be commercially attractive and tocover costs of production and development.These species are those requiring optimal soiland water conditions. Possible requirementsfor fertilizer and other inputs for such crops

—

59

are summarized in a report prepared for theNational Science Foundation (22).

Another potential strategy is represented bythe selection and development of native plantsadapted to saline environments. The ability totolerate environmental constraints and stillproduce utilitarian byproducts is one potentialavenue for overcoming high fertilization in-puts. This is an approach to native plant de-velopment that has been virtually ignored inplant research. The existence of salt tolerantwild selections of existing crops could improvethe infertility tolerance of these species andtherefore reduce their needs for fertilization.Such possibilities will require concerted effortsto enhance the range of adaptability for mostcrop species.

Pesticides

Very few, if any, of the native plants havinga high potential for development have beenstudied from the aspect of insect, disease, orweed problems normally associated with inten-sive cultivation, Whereas many insect or dis-ease organisms may be held in check in a di-verse plant community, they may increase toepidemic proportions when their host plant isgrown in a pure stand. An example of such anepidemic occurred when black grass bug pop-ulations nearly devastated pure stands of in-troduced wheatgrasses that had been seededto replace sagebrush and other plants in west-ern rangelands (9). Plantings of native specieswill require research and plant protectionmeasures similar to those already necessary forthe production of conventional crops.

In tropical countries where multicroppingsystems represent the most sustainable methodof farming systems, the pesticide requirementscould be minimized by host/predator interac-tion within the farm plots (7), Testing and de-velopment of such models needs to be greatlyexpanded, however.

Irrigation

Requirements for irrigation will depend onthe kind of native plant selected. As a concept,the use of native plants indicates an adaptabil-ity to the specific environment and its con-straints. Species adapted to tropical soils maynot require irrigation if the pattern of rainfallis adequate and meets the critical stages ofplant development. Areas of subtropical soilstypically have periods of rainfall deficiency andvarious strategies must be employed to obtainproduction under such conditions, These strat-egies include:

1.

2.

3.

Choose native plants with low water re-quirements that can be grown in desert orsemi-desert conditions. Some examplesare: jojoba, atriplex, guayule, buffalogourd, guar, cassia, acadia species (19).Develop technologies to increase the effec-tiveness of natural precipitation or irriga-tion. Alternate fallow, spaced plantings,water harvesting, or drip irrigation can beeffective. Where land is not a limiting fac-tor, these extensive practices can be eco-nomically effective. Evanari, et al. (4), dem-onstrated how an ancient civilizationsurvived in the Negev desert by using pre-cipitation optimizing practices such aswater harvesting and spaced plantings. Re-cent work at the University of Arizona (6)indicates high potential for using waterharvesting to foster plant production un-der desert conditions. Biomass plantings,deep rooted tree crops, and droughtadapted species would be most suitable forthese technologies.Use available irrigation water to supportmaximum production of new crops fromhigh yielding native plants. Where soilswith a high productive potential may beavailable for intensive use, possibly byreplacing a lower value traditional cropwith a high value new crop, irrigation may

38-846 0 - 85 - 3

60

be justified. Close plantings, tillage, pestcontrol, and fertilization may also beneeded to optimize production. Grainamaranth, winged bean, and guar are pos-sible species for intensive development,but many other may be considered.

Machinery

Because of the varied nature of native spe-cies available for development, no definitestatement can be made regarding machineryrequirements. Equipment for land preparation,tillage, and transportation of crops to storageand market would be needed. Harvesting maybe done by machinery in the case of a uniformplant such as guar or guayule where leaves andseeds are easily available. Where fruits, stems,

or roots are not uniformly exposed and are re-tained on the plant, either hand labor or a spe-cialized piece of machinery may be needed.

In regions of the world where hand labor isabundant for planting, cultivating, and har-vesting, the development of new native cropsthat require hand labor rather than machineryis most appropriate. In other nations, labor in-tensifying machinery can be developed, Thishas been the pattern followed in the develop-ment of conventional crops.

It is important to recognize that the devel-opment of native plants for their various usescan be aimed at local needs as well as at widerindustrial and international markets. Machin-ery and labor requirements will depend onwhat level of development is pursued.

WHAT IS THE POTENTIAL ROLE Of NATIVE PLANTS TO RESTORE,IMPROVE, OR SUSTAIN FOOD PRODUCTION ON TROPICAL AND

SUBTROPICAL SOILS?

There is a high potential for some nativeplants to positively affect food production ontropical and subtropical soils. One of the mostpromising strategies is the increased use of le-guminous plants as food, livestock fodder, andwood to concurrently improve soil fertility (21).As fertilizer costs continue to escalate in re-sponse to energy expenses, fertilizers will be-come economically prohibitive in many devel-oping countries. Incorporation in the croppingsystem of a legume rotation, green manure, oranimal manures derived from legume feedsmay be the best remaining option to replacefertilizers (12) and maintain agriculturalproductivity.

Non-legume native species have variouspotentials for positive benefits to food produc-tion. Many species are already known locallybut have not received sufficient notice to be in-troduced or developed for use in other (simi-lar) regions. To achieve such recognition willrequire:

1

2

3

A shortage in food from existing cropplants.Development of new lands that are bettersuited for new crops.Adaptation of new crops to compete eco-nomically with conventional crops,

Some form of research and development in-tervention will be needed to raise the perspec-tive and incentives of local peoples. The like-lihood of general use depends on the individualspecies. For example, the general qualities ofseeds from the jojoba plant have been knownfor many years (10) but only recently has anydevelopment effort appeared substantialenough to bring the plant into widespread use,

The shortage and cost of sperm whale oil isa big factor motivating jojoba development inmore than five countries. Some applicationswill be less spectacular, but no less needed.P1antings of the legume tree Acacia albida inMali (24) hold considerable promise for im-

61

proving subsistence agricultural productionthere, but the effort is but a “drop in thebucket” compared with the needs in that areaof West Africa.

In view of the diversity of native plants avail-able for development and the number of coun-tries with suitable environments, judicious sup-port of native plant development programs

seem justified. The likelihood of spontaneousdevelopment or widespread use of native plantresources seems unlikely without external en-couragement. Otherwise, many useful nativeplant species and ecotypes stand in jeopardyof being lost as deforestation, land depletion,industrial development, or other activities elim-inates the natural plant communities.

WHAT RESEARCH, DEVELOPMENT, AND IMPLEMENTATIONSCENARIOS COULD HELP NATIVE PLANTS REALIZE THEIR POTENTIAL

OF ENHANCING TROPICAL SOIL PRODUCTIVITY?

Scenario A

The program of planting seedlings of Acaciaalbida legume trees in Mali (24) serves as amodel for the development of the potential ofa native plant. In this program, CARE set upproduction nurseries to produce tree seedlingsin soil-filled plastic tubes. Acacia albida is anindigenous legume tree native to sub-SaharanAfrica. The tree has the unique feature of be-ing leafless during the rainy season. This al-lows for cultivation of other crops directly un-der the tree. The leaves and pods providefodder and green manure and the roots fix ni-trogen. It is an ideal candidate for selection,improvement, and application to various semi-arid agroforestry systems.

Teams of local farmers were employed toplant the seedlings in preselected agricultural/pasture areas of good soils. Planters were paidon a per tree basis for planting and protection.Subsequently, these local people were encour-aged (in their work training orientation) to takea special interest in the seedlings to see thatthey received appropriate management andprotection to ensure their survival from graz-ing animals. Benefits expected are increasesin soil productivity and livestock feed.

Scenario B

A scenario for planting a living fence of a leg-ume shrub to enhance soil fertility by N-fixation and livestock manure might be as fol-

lows. Seedlings could be propagated at a gov-ernment research station after selection fromdepleted stands of palatable shrubs. Theseplants would then be distributed to villageelders for allocation to heads of families forplanting around the fields and houses in theimmediate vicinity of the village. This wouldenhance kitchen garden production and feedsmall livestock through the dry season, Excessfodder could be used on the farm plots as greenmanure.

Scenario C

A scenario to develop a high value, nativetree, fruit crop would logically start with a pro-gram of selecting the most desirable biotypesfor their fruit quality, tree size and form, andmaturity pattern. Because of the long-term re-quirements for genetic improvements thatwould combine the best qualities in variousselections, a dual development program wouldbe undertaken. The first would be to vege-tatively propagate (by rooted cuttings of a fewplants or by tissue culture for thousands) thebest selection(s). Propagules would normallybe grown in containers until ready for fieldtransplanting. Sufficient acreage would beplanted to provide experience in intensivemanagement and production for a local, re-gional (city), or international cash market. Asexperience is gained with product acceptance,the criteria for the genetic breeding program

62

would be modified, By the time suitable genetic Levels of capital and manpower neededmaterials would be available, the market re- could be determined or extrapolated on thequirements would be sufficiently known to “ basis of experience with a pilot program. Pi-guide large-scale development plantings and lot demonstration programs are a plausibleimproved cultural practices, possibly involv- way to approach development of the mosting machinery. promising native plants,

One of the most critical attitudinal problemsin developing new crops from native plants isone of institutional interest in sustainableand diversified plant development. Traditionalcrops, mostly of temperate origin, have re-ceived the majority of institutional attentionfrom government, research, and commercialorganizations. A new and more innovative ap-proach to plant development is required whenreferring to native or adapted plant develop-ment. The various groups that directly affectthese development efforts include the fol-lowing:

Cultivators

All efforts should include the local farmers.The objective would be to seek sufficient in-volvement on planning, planting, and manage-ment to bring local people to thinking that theproject is theirs—not something imposed fromoutside by government. The active efforts ofan individual farmer in the Dakotas to bringsunflower into widespread cultivation is an ex-ample of the importance of this element in theintroduction of “new” crops.

LegisIators

Politicians should be encouraged to providea favorable and stable policy for product de-velopment, to be optimistic but not raiseunrealistic expectations, and finally to be will-

ing to support financial needs of the pilot proj-ect. The efforts of the Guayule Commission isan example of this coordinated effort at pol-icy and implementation.

Financiers

Banks and bankers need to be educated aboutthe realities and potentials for development ofa new crop. Available capital for second phasedevelopment would be needed if the privatesector is to follow the pilot development. Orien-tation and involvement would be needed toassure support when it is needed. Tax incen-tives and loan guarantees may be useful waysfor financial institutions to foster more rapiddevelopment and diversification of new crops.

International

Policymakers within the international donorcommunity need to understand the risks aswell as the opportunities for a successful pro-gram. Stepwise project implementation is adesirable approach where needed research anddevelopment experience is gained as the pro-gram develops. This approach could be imple-mented directly by requiring agricultural, for-estry, and horticultural development projectsto direct a certain percentage of the programto native species or varieties. Means for involv-ing host country politicians, research people,and local farmers are crucial.

WHAT BIOPHYSICAL, CULTURAL, AND SOCIOECONOMIC CONDITIONSWOULD BE CONDUCIVE TO PROJECT IMPLEMENTATION?

Obviously, the best place for a native plant needed most. However, there are qualificationsdevelopment project would be where it is to this simplistic statement.

63

Blophysical Conditions

To be successful, a native species needs ahigh degree of adaptation to the climate, soils,topography, and animal uses, including resis-tance to parasites. From an ecological stand-point, the approach should be to seek areas thatare ecologically equivalent to the original hab-itat of the native plant species. This is usuallydone by testing plantings in various locationsof similar climate. However, the time periodduring which the plantings are under obser-vation may not be sufficient to experience therange of environmental extremes that is com-mon to the area. Detailed experiments undergreenhouse and controlled environment cham-bers may help to document the full range ofadaptation possessed by the species.

For a new crop or agricultural product to besuccessfully produced, it must not be contraryto the cultural traditions of the people to grow,consume, or use. For example, an improvedhigh protein maize (corn) variety was consid-ered in India, where there were food shortages.However, the yellow color of the seed coat wasobjectional because it resembled a grain prod-uct fed to animals (l). A social custom studywould be advisable to determine if any taboos,customs, or adverse values exist regarding thepotential crop and its required productionpractices,

Socioeconomic Conditions

Critical to the development of any new cropfrom a native plant is whether the product issocially acceptable and whether local peoplecan handle the costs of development. There isless chance of gaining social acceptance of aproject if the payoff period is far into the fu-ture. An early return on the investment maybe needed to maintain interest and commit-ment to a project. Further, the amount of cap-ital required may exceed the capacity of in-dividuals or banks to handle. Thus, smallerincrements of development and interim returnsto investment may be necessary. An examplewith animals should illustrate this point. Afarmer could finance the purchase of severalanimals of an improved breed of goat or a penof rabbits, but he may not be able to financea cow or bull. There is also greater risk in hav-ing a high amount of capital tied up in one in-dividual.

The above conditions are most likely to ex-ist in the less developed tropical countries, inthe more rural and remote regions of such acountry, and with people of tribal or nomadicsocial organization. The less educated peoplewould likely be more difficult to reach and lesswilling to accept a development program,

Communication tools such as radio, news-papers, and films could be used to help bothin the search for useful plants as well as dis-seminate information on new uses and oppor-tunities for economic diversification.

WHAT ARE THE MAJOR CONSTRAINTS ON DEVELOPMENT ANDIMPLEMENTATION OF NATIVE PLANT USE?

Development of a native plant species to Scientific Constraintscommercial or economically significant levelswould not be easily accomplished based on A major scientific problem in plant develop-current observations of jojoba and guayule. ment is lack of technical information. A suffi-Many constraints must be overcome to satis- cient amount of general information is neededfactorily develop the potential of a native plant. to identify plants of high potential. Additional

64

species information can help determine feasi-bility for development and the suitability ofproducts or uses to meet identified needs. Prog-ress toward development may well depend ontechnical data regarding planting, manage-ment, harvest, processing, and conservation.Pilot demonstration programs designed to an-swer technical problems are essential.

Particularly needed are scientific studies onways to establish plants and obtain optimumproductivity under arid, semiarid, and tropi-cal conditions. Problems dealing with micro-organisms and plant growth, drought resis-tance, physiology of stress, and application ofengineering to improve adaptation presentchallenges for scientific research on indige-nous plants.

Environmental Constraints

Existing land uses may pose one of thelargest constraints to native plant development.But such commitments of land must be seenin relation to the long-term values. Where de-creasing soil fertility and vegetation degrada-tion are occurring, a shift to a leguminous na-tive plant could bring multiple benefits. Fornative plants with industrial potential (i.e.,guayule), processing may influence air andwater quality. Whether costs can be internal-ized in the value of the product of plant usemust be determined. In most instances, theenvironmental benefits of developing native oradapted plants will most likely outweigh thenegative impacts. The potential to reduce ex-isting environmental degradation and moresustained land use must be considered positiveconsequences.

Culture Constraints

Native plant development may cause socialchange, community growth, and increasedneed for services. Such changes need to be ad-dressed, but at this time little information isavailable. In general, the cultural impacts fromdeveloping new crops or practices from nativeplants should be positive or neutral. In the con-text of tropical countries, the perceptions of re-

gional, community, tribal, or family groupsmust be considered. Resistance to change maybe manifested by refusal to cooperate or allowproject development. Involvement of localleaders and decisionmakers is a necessity.

Economic Constraints

The major economic constraint to develop-ment is probably the lack of seed money, ven-ture capital, or government support to conductpilot-scale programs. From the pilot program,cost data can be extrapolated for planting, pro-duction, transportation, and marketing. Fromthese preliminary data, decisions can be madetoward major financing and long- or short-termcommitment of funds, either by the private sec-tor or through government grants and loans.Because of the generally speculative nature ofdeveloping high potential native plants to meetneeds that are not clear, private sector fund-ing may have to be government subsidized.

Political Constraints

A major political constraint is the instabil-ity and short longevity of many political leadersin less developed countries. Although a newcrop development program may be highly fa-vored by one political leadership, the prospectof change must be considered. Because agri-cultural development is highly important andnot as politically sensitive as other sectors ofa country, it should be possible to work withinpolitical constraints as long as the project doesnot appear to run counter to current politicaland social philosophy.

For example, pilot plantings of palatable fod-der shrubs in Syrian rangelands by FAO andthe Syrian Ministry of Agriculture were de-scribed as an extension of cooperative market-ing and fattening units to increase meat pro-duction and increase the stability of thelivestock industry (2). In reality, the system hadmany free enterprise profitmaking opportuni-ties to increase the incentive of individuals toparticipate in the scheme. Yet political leaderstouted the success of this cooperative projectand declared it to be in harmony with the so-

cialistic philosophy mandated by the govern- provide benefits equitably. Additionally,ment. New crops must not appear to compete adapted crops that could represent a higherwith existing production systems, but should cash return than traditional crops should re-complement them. Constituents must be con- ceive special attention from the internationalvinced that the proposed developments will donor community.

HOW WOULD IMPLEMENTATION OF A NATIVE PLANT TECHNOLOGYAFFECT THE NEED

Because of the varied types of native plants,no specific capital requirements can be deter-mined for all native plants. There is no doubtthat a native plant development program wouldrequire significant inputs of technology andcapital. However, those plants that produce acrop would require greater inputs than thoseused for reforestation, improving soil fertility,or increasing rangeland forage production.

Careful analysis of the infrastructure of a re-gion or county may give an indication of avail-able processing capacity. For example, vege-

FOR CAPITAL?

table oil extraction facilities are available in thegroundnut basin of Senegal and might be avail-able in the off-season to extract hydrocarbonlatex from giant milkweed plants that grow inwaste places and margins of fields. A smallpilot program with these native plants couldprovide some of the data necessary to deter-mine the feasibility of proceeding to largerphases of development. In a like manner, anyproposed new crop should be analyzed for cap-ital inputs and available facilities for produc-tion processing and transport.

WHAT WOULD BE THE IMPACT OF WIDE-SCALE IMPLEMENTATION OFNATIVE PLANT USE ON SOCIOECONOMIC STRUCTURE?

It would be false to assume that only a largecommercial-type farm or a family-sized farmwould be suitable for native plant development.Much depends on the nature of the plant spe-cies and the magnitude of development nec-essary. From table 1, it can be seen that somecrops such as cocoyam and buffalo gourdcould easily be grown on small plots and col-lected for commercial markets. In contrast, in-dustrial feedstocks, biomass, and high volumecrops such as guayule, ramie, leucaena, andguar would better be grown in large fields andbe harvested and treated mechanically.

Small field operations would cause littlechange on socioeconomic structure except toprovide an additional income stream to com-munities, Large operations may disrupt com-munities by increasing their population or re-quiring the establishment of new communities.An excellent example in the United States isthe 110,000 acre Navajo Irrigation project near

Farmington, New Mexico. This large commer-cial farm operation has left little opportunityfor community development of a traditional na-tive culture, nor has it provided an opportu-nity for family farm or cooperative group farmdevelopment. The project has addressed onlythe large-scale production-economic aspects ofdevelopment. Socioeconomic problems remainunsolved as illustrated by the attempts beingmade to resettle Navajo workers in a modernsubdivision quite foreign to existing patternsof community settlement.

In summary, the various options available innative plants of high potential for developmentcould enhance existing social and economicpatterns or could disrupt them with large de-velopments depending on the suitability of theland, the adaptability of native plants to givenlocations, and the institutional insensitivity thatmight prevail in their development.

66

References

1. Cummings, Ralph, personal communicationfrom the Rockefeller Foundation Project Direc-tor in India, 1972.

2, Draz, Omar, personal communication while ona field trip to Waddi A1-Azib Experiment Sta-tion in Syria, 1978.

3, Epstein, E. et al., “Saline Caltese of Crops: AGenetic Approach, ” Science 210:399-404, 1980.

4, Evanari, Michael; Shanan, Leslie; and Todmor,

5

Naphtali, The Negev, the Challenge of a Desert(Cambridge, MA: Harvard University Press,1971), 345 p.Felker, Peter, “Mesquite, An All-Purpose Legu-minous Arid Land Tree, ” pp. 89-132. In:Ritchie, Gary A. (cd.) New Agricultural Crops,AAAS Selected Symposium 38 (Boulder, CO:Westview Press, 1979)0

6. Frasier, G. W., “Proceedings of the Water Har-vesting Symposium, ” U.S. Department of Agri-culture, Agricultural Research Service, WesternRegion (ARS) W-22, 1975, 329 pp.

7. Gliessman, S., “The Ecological Basis for the Ap-plication of Traditional Agricultural Technol-ogy in the Management o f Trop ica l

8.

9.

10.

110

12.

Agroecosystems,” Agroecosystem (in press),1980.Goodin, Joe R., and David Worthington (eds.),“Arid Land Plant Resources,” Proc. of the In-ternational Arid Lands Conference on Plant Re-sources, Texas Tech. University, Lubbock, TX,19790

Haws, B. Austin (cd.), “Economic Impacts ofLabops hesparius on the Production of HighQuality Range Grasses,” final report of UtahAgric. Exp. Stn. to Four Corners Regional Com-mission, Utah State University, Logan, UT,1978, 269 pp.Hogan, Le Moyne, “Jojoba, A New Crop forArid Regions,” pp. 177-205. In: Ritchie, GaryA. (cd.), New Agricultural Crops, AAASSelected Symposium Series 38 (Boulder, CO:Westview Press, 1979).McKell, C. M., “Shrubs-A Neglected Resourceof Arid Lands, ” Science 187:803-809, 1974.National Academy of Sciences, “PreliminaryReport Assessment of Environmental Degrada-tion and Agricultural Productivity in the

13.

14,

15.

16.

17s

18,

19,

20,

21,

22,

23

24

Senegalese Groundnut Basin, ” NAS report toAID, Senegal, 1980.National Academy of Sciences, Tropical Le-gumes: Resource for the Future, report of adhoc panel of the advisory committee on tech-nology innovation, 1979.National Academy of Sciences, Guayule: AnAlternate Source of Natural Rubber, report ofad hoc panel of the advisory committee on tech-nology innovation, 1977.National Academy of Sciences, Leucaena,Promising Forage and Tree Crop for the Trop-ics, report of ad hoc panel of the advisory com-mittee on technology innovation, 1977.National Academy of Sciences, Products FromJojoba: A Promising New Crop for Arid Lands,report of ad hoc panel of the advisory commit-tee on technology innovation, 1975.National Academy of Sciences, The WingedBean: A High Protein Crop for the Tropics, re-port of ad hoc panel of the advisory committeefor technology innovation, 197.5.National Academy of Sciences, UnderexpZoitedTropical Plants With Promising Economic Val-ue, report of ad hoc panel of the advisory com-mittee on technology innovation, 1975.Revelle, Roger, “Flying Beans, Botanicalwhales, Jack’s Beanstalk and Other Marvels, ”National Academy of Sciences, Board onScience and Technology for International De-velopment, 1978.Ritchie, Gary A,, New Agricultural Crops,AAAS selected symposium series 38 (Boulder,CO: Westview Press, 1979), 259 p.Sherman, P. M., “Tropical Forage Legumes, ”Food and Agricultural Organization of theUnited Nations, Rome, Italy, 1977.Soil and Land Use Technology Inc., “Feasibil-ity of Introducing Food Crops Better Adaptedto Environmental Stress, ” National ScienceFoundation Report NSF/RA 780289, 1978.Thalen, D. C. P., EcoZogy and Utilization of Des-ert Shrub Rangelands in Iraq (Dr. W. Junk Pub-lishers, The Hague Netherlands, 1979), 448 p.Weber, Fred, and Dulansey, M,, “MidpointEvaluation, Chad Reforestation Project, ” Pre-pared for CARE by Consultants in Develop-ment, New York, NY 10014, 1978.

Chapter V

Multiple Cropping Systems:A Basis for Developing an

Alternative Agriculture

Dr. Stephen R. GliessmanEnvironmental Studies

University of California

Contents

Page

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69Concepts and Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70The Basis of Multiple Cropping. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Yield Advantages of Crop Mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71General Resource Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73Specific Resource Use, Conservation, and Management . . . . . . . . . . . . . . . . . . . . . 75Agroforestry: A Multiple Cropping System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79Socioeconomic Implications of Multiple Cropping Systems:

Perspectives for the Future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

List of Tables

Table No. Page

l. Definitions of the Principle Multiple Cropping Patterns . . . . . . . . . . . . . . . . . . . . . . 712. Related Terminology Used in Multiple Cropping Systems . . . . . . . . . . . . . . . . . . . . 713. Biological and Physical Factors: The Advantages and Disadvantages of Multiple

Cropping Systems Compared to Sole-Cropping or Monoculture Systems. . . . . . . . 724. Social and Economic Factors: The Advantages and Disadvantages of Multiple

Cropping Systems Compared to Sole-Cropping or Monoculture Systems . . . . . . . . 73S. Yields of Corn, Beans, and Squash Planted in Polyculture as Compared to Low

and High Densities of Each Crop in Monoculture . . . . . . . . . . . . . . . . . . . . . . . . . . 746. Effects of Mixed and Row Intercropping on Yields and Nutrient Uptake of

Corn and Pigeon Peas in St. Augustine, Trinidad, Expressed as Relative YieldTotals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

7. Biomass Distribution of Dry Matter in a Corn/Bean Polyculture as Compared toa Corn Monoculture, in Tacotalpa, Tabasco, Mexico . . . . . . . . . . . . . . . . . . . . . . . . . 76

8. Classification and Examples of Agroforestry Technologies. . . . . . . . . . . . . . . . . . . . 80

Figure

Figure No. Page

l. Distribution of the Relative Yield Totals of Mixtures Based on 572 PublishedExperiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Chapter V

Multiple Cropping Systems:A Basis for Developing an

Alternative Agriculture

This paper presents a general discussion ofthe concept of multiple cropping, including adescription of the different types of systems,and the advantages and disadvantages of theirwidespread use, both biological and socio-economical. These systems are designed to in-tensify agricultural production both in termsof yields per unit area and through the moreefficient use of space and time.

Examples of yield increases with multiplecropping systems are expressed in terms ofRelative Yield Totals (RYT) or Land EquivalentUse (LER) where the production per unit areawith the multiple crops is greater than the sumof equivalent areas planted to monoculture.This increase in production is explained byhigher overall efficiency of resource use.

Specific examples of the effects of multiplecropping systems on resource use, conserva-tion, and management are discussed, Variablesconsidered include microclimate, light, soil,water, pests, diseases, weeds, crop interac-tions, space, and time. The special case ofagroforestry, which combines trees with cropsand grasses, is discussed.

In conclusion, the socioeconomic implica-tions, both advantageous and disadvantageous,are discussed. Also, the great potential formultiple cropping systems in agriculture in theUnited States is presented. Research needs tobe directed to test these alternatives.

Multiple cropping is not a new form of agri-cultural technology, but instead is an ancientmeans of intensive farming. Multiple croppinghas been practiced in many parts of the worldas a way to maximize land productivity in aspecific area in a growing season. Generally,the practice of planting two or more crops onthe same field is more common in tropical re-gions where more rainfall, higher tempera-tures, and longer growing seasons are morefavorable for continual crop production. Aspopulation has increased, increasing the needfor agricultural production, the use of multi-

cropping systems is more prevalent. Thoughthe history of multiple cropping is old, the con-cept has received very little attention from agri-cultural scientists, and what limited interest ex-ists has come about very recently.

Why was this interest increased so dramat-ically in such a short time? Food shortages inmany parts of the world, as well as the threatof insufficient supplies in the near future, con-tinues to stimulate more intensive agriculturalinvestigation in a search for more productivealternatives. As a consequence, it appears that

69

70

we are about to embark on a new phase of agri-cultural research. Exactly what form it will takeis still not known, but the reasons for this newapproach are rapidly becoming apparent.

First, we have begun to observe a leveling offin yield increases brought about by the typesof genetic manipulation that gave us such rapidand impressive yield increases during the“Green Revolution.” It is as if we have reacheda “yield plateau” with the current lines of re-search and crop selections. Large-scale use ofsingle varieties (e.g., some of the InternationalRice Research Institute (IRRI) varieties of rice),with broad adaptability, produced major break-throughs in yields. But it appears that these va-rieties have almost reached their maximumyield potentials. In many areas with specificsoil and climatic conditions, they have not per-formed as well as hoped, especially on landmore difficult to mechanize or irrigate. Thuswe must begin to look for varieties with morespecific adaptability and selected for specificenvironments, or else consider alternativecropping systems.

best agricultural lands–areas with good soiland easy water control. Future increases inproduction, therefore, will demand a new andinnovative way of managing these highly pro-ductive lands, as well as looking for methodsto make marginal lands increasingly produc-tive. Only 20 percent of Asia rice land, for ex-ample, is irrigated, and the new high yieldingrice varieties (which also require high levels offertilizers, water use, and pest control) have notpenetrated much beyond this boundary (16).

The third factor is the oil crisis. Oil pricescontinue to soar, and with them, the cost offer-tilizers, pesticides, and fuel needed to build andrun farm equipment and move irrigation water.Costs continue to mount for those inputs mostresponsible for achieving the dramatic yield in-creases of the “Green Revolution. ” We arefaced with the necessity of having to considerother alternatives that might allow us to sub-stitute innovative biological or agronomic prac-tices and varieties for these high cost inputs.Multiple cropping offers one of the most im-portant and promising of these alternatives.

Second, most of the dramatic yield increasesduring the past few decades have been on the

CONCEPTS AND DEFINITIONS

Multiple cropping systems use managementpractices where the total crop production froma single piece of land is achieved by growingsingle crops in close sequence, growing sev-eral crops simultaneously, or combining singleand mixed crops in some sequence. The mostimportant aspect of multiple cropping is theintensification of crop production into addi-tional dimensions. Multiple cropping includesthe dimensions of time and space; for exam-ple, when two crops share the same space atthe same time.

A classification of types of multiple croppingsystems is presented in table 1. Note thatspecial emphasis is placed on the distinctionbetween intercropping, where two or morecrops are grown at the same time, and sequen-

tial cropping, where two or more crops aregrown on the same piece of land, but one fol-lowing the other.

Some additional terms used in multiple crop-ping are presented in table 2. Agroforestry, asa particular type of intercropping system, willbe discussed in some detail. Also, “mixed crop-ping, “ “polyculture,” and “multiple cropping”will be used interchangeably in this review. Bycombining different aspects of simultaneousand sequential cropping systems, it is possibleto visualize a truly complex pattern of differentmultiple cropping systems. This classificationwill be used throughout the following discus-sion, based on a symposium sponsored by theAmerican Society of Agronomy, in support ofthe need to standardize terminology (34).

—

71

Table 1 .—Definitions of the Principal MultipleCropping Patterns

● Multiple Cropping: The intensification of cropping in timeand space dimensions. Growing two or more crops on thesame field in a year.

c Intercropping: Growing two or more crops simultaneouslyon the same field per year. Crop intensification is in bothtime and space dimensions. There is intercrop competi-tion during all or part of crop growth. Farmers manage morethan one crop at a time in the same field.—Mixed intercropping: Growing two or more crops simul-

taneously with no distinct row arrangement.— R o w intercropping: growing two or more crops

simultaneously with one or more crops planted in rows.—Strip intercropping: Growing two or more crops simul-

taneously in different strips wide enough to permit in-dependent cultivation but narrow enough for the cropsto interact agronomically.

—Relay intercropping: Growing two or more crops simul-taneously during part of each one’s life cycle. A secondcrop is planted after the first crop has reached itsreproductive stage of growth, but before it is ready forharvest.

● Sequential Cropping: Growing two or more crops i n se-quence on the same field per year. The succeeding cropis planted after the preceding one has been harvested. Cropintensification is only in the time dimension. There is nointercrop competition. Farmers manage only one crop ata time.—Double cropping: Growing two crops a year in sequence.— Triple cropping: Growing three crops a year in sequence.—Quadruple cropping: Growing four crops a year in se-

quence.—Ratoon cropping: Cultivating crop regrowth after harvest,

although not necessarily for grain.SOURCE Andrews and Kassam, 1976 (5)

Table 2.— Related Terminology Used in MultipleCropping Systems

Single Stands: The growing of one crop variety alone in purestands at normal density. Synonymous with “solid plant-ing, “ “sole cropping. ” Opposite of ‘(multiple cropping. ”

Monoculture: The repetitive growing of the same crop on thesame land.

Rotation: The repetitive growing of two or more sole cropsor multiple cropping combinations on the same field.

Cropping Pattern: The yearly sequence and spatial arrange-ment of crops, or of crops and fallow on a given area.

Cropping System: The cropping patterns used on a farm andtheir interactions with farm resources, other farm enter-prises, and available technology that determine theirmakeup.

Mixed Farming: Cropping systems that involve the raisingof crops and animals.

Cropping Index: The number of crops grown per annum ona given area of land multiplied by 100.

Relative Yield Total (RYT): The sum of the intercropped yieldsdivided by yields of sole crops. The same concept as landequivalent ratios. “Yield” can be measured as dry matterproduction, grain yield, nutrient uptake, energy, or proteinproduction, as well as by market value of the crops.

Land Equivalent Ratios (LER): The ratio of the area neededunder sole cropping to the one under intercropping to giveequal amounts of yield at the same management level.The LER is the sum of the fractions of the yields of theintercrops relative to their sole-crop yields. It is equivalentto RYT, expressed in commercial yields.

Income Equivalent Ratio (IER): The ratio of the area neededunder sole cropping to produce the same gross incomeas is obtained from 1 ha of intercropping at the samemanagement level. The IER is the conversion of the LERinto economic terms.

SOURCE Sanchez, 1976 (39)

THE BASIS OF MULTIPLE CROPPING

Yield Advantages of Crop Mixtures

In areas of the world where multiple crop-ping is a common aspect of agroecosystemmanagement, productivity generally is morestable and constant in the long term (24,45).Farmers often are able to achieve a combinedproduction per unit area greater with a cropmixture than with an equal area divided amongseparate crop units. In such cases the RelativeYield Total (RYT) is greater than 1.0. It maybe that each crop in the mixture yields slightlyless than the monoculture, but the combined

yield of the mixture on less total land area isthe important aspect.

In one study (43), the results of 572 c o m -parisons of crop mixtures demonstrated thatthe majority (66 percent) had RYTs close to 1.0,indicating no distinct advantage to the mixture(fig. 1). On the other hand, 20 percent of themixtures had RYTs greater than 1.0, rangingup to 1.7, indicating advantages to the mix-tures. Only 14 percent had less than 1.0, in-dicating distinct disadvantages. It must beremembered that most of the cases studied

72

Figure 1 .—Distribution of the Relative Yield Totals ofMixtures Based on 572 Published Experiments

0.5 0.7 0.9 1.1 1.3 1.5 1.7

Relative yield totals (RYT)

SOURCE Trenbath, 1974(43)

were experimental planting and not actualmultiple cropping systems. Farmers wouldtend to choose the systems that yield more, aswe have observed in traditional agroecosys-tems in the lowland tropical areas of southeast-ern Mexico (24,25).

The fact that advantageous mixtures do ex-ist demonstrate the need for detailed researchto take proper advantage of such systems. Butfor such systems to be considered as actualalternatives we need to understand thoroughlythe biological and agronomic basis responsi-ble for the observed response, as well as theadvantages and disadvantages to their use.Before beginning a discussion of each aspect,a basic outline of such characteristics is pre-sented, separated broadly into biological andphysical aspects (table 3) and socioeconomicaspects (table 4). In many cases it is understoodthat there may be overlap between the twoclassifications, yet it is hoped that in the courseof the following discussion that such aspectswill be clarified.

Table 3.—Biological and Physical Factors:The Advantages and Disadvantages of Multiple

Cropping Systems Compared to Sole-Cropping orMonoculture Systems (priority is not established)

Advantages -

1. It is possible to obtain a better use of vertical space and

2.

3.

4.

5.

6.

7.8.9.

10.

11.

12.

13.14.

15.

16.

time”, imitating natural ecological patterns in regards tostructure of the system, and permitting efficient captureof solar energy and nutrients.Greater amounts of biomass (organic matter) can bereturned to the system, sometimes even of better quality.There exists a more efficient circulation of nutrients, in-cluding their “pumping” from the deeper soil profileswhen deeper rooted shrubs or trees are included.The damaging effects of wind sometimes can bereduced.Systems can be designed that are appropriate for (butnot restricted to) marginal areas because multiple crop-ping systems can better take advantage of variable soil,topography, and steeper slopes.Multiple cropping systems are less subject to variabili-ty in climatic conditions, especially extremes of rainfall,temperature, or wind.Reduction of water evaporation from the soil surface.Increased microbial activity in the soil.Avoidance or reduction of surface erosion.Fertilizer use can be more efficient because of the morediverse and deeper root structure in the system.Improved soil structure, avoiding the formation of a “hardpan” and promoting better aeration and filtration.Legumes (as well as a few other plant families) are ableto fix and incorporate nitrogen into the system.Heavier mulch cover aids in weed control.Better opportunities for biological control of insects anddiseases.Crop mixtures better permit the functioning of complexmutualisms and beneficial interactions between or-ganisms.Better use of time, with more crops per unit time in thesame area.

Disadvantages1.2.3.4.

5.

6.

7.

8.

9.

10.

11.

12.

Competition between plants for light.Competition between plants for soil nutrients.Competition between plants for water.Possibility for allelopathic influences between differentcrop plants due to plant-produced toxins.Harvesting of one crop component may cause damageto the others.It is very difficult to incorporate a fallow period into multi-ple cropping systems, especially when long lived treespecies are included.It is sometimes impossible, and many times very difficult,to mechanize multiple crop systems.Increased evapotranspiration loss of water from the soil,caused by greater root volume and larger leaf surfacearea.Possible over-extraction of nutrients, followed by theirsubsequent loss from the system with the increased ex-portation of agricultural or forest products.Leaf, branch, fruit, or water-drop fall from taller elementsin a mixed crop system can damage shorter ones.Higher relative humidity in the air can favor disease out-break, especially of fungi.Possible proliferation of harmful animals (especiallyrodents and insects).

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Table 4.—Social and Economic Factors:The Advantages and Disadvantages of Multiple

Cropping Systems Compared to Sole-Cropping orMonoculture Systems (priority is not established)

A d v a n t a g e s

1.

2.

3.

4.5.

6.7.

8.

Dependence on one crop is avoided so that variabiIity I nprices, market, climate, and pests and diseases do nothave such drastic effects on local economics,Less need to import energy, pay for fertilizers, pay for ex-ternally produced materials, or depend on machinery,WiIdlife is favored, and with rational use it can be an im-portant source of protein.Greater flexibility of the distribution of labor over the yearRecovery of investments can occur in much less time,especially where trees are combined with short termagricultural crops,Harvest is spread over a longer period of time,In areas and times of high unemployment, multiple crop-ping systems can use much more labor.Farmers can produce a large variety of useful products,depending on the type and complexity of the multiplecropping systems, such as firewood, construction mate-rials, flowers, honey, crops for home consumption, thuslowering the outflow of funds,

9. Certain multiple cropping systems permit a gradualchange from destructive farming practices to more ap-propriate technologies, without a drop in productivity,

10, Multiple cropping can promote a return to the land, andits maintenance.

11. In systems which include trees and/or animals, such com-ponents can constitute a type of “savings” for the future,while short term crops satisfy immediate needs.

12. Because of their diverse nature, multiple cropping sys-tems promote interdisciplinary activities, stimulate inter-change and group activities, and lead to social cohesionin the long term,

Disadvantages1. The systems are more complex and less understood

agronomicalIy and biologically. Statistical designs for ex-perimental analysis are much more complex.

2. Yields sometimes are lower, providing only subsistencelevel production.

3. In many systems, multiple cropping is not considered tobe economically efficient due to the complexity of ac-tivities necessary.

4. These systems require more hand labor, which can beconsidered a disadvantage in some circumstances.

5. Some mixed crop systems do not offer sufficient rewardto lower income farmers to raise their standard of living.

6. For producers with limited economic resources, it maytake longer to recover the entire initial investment.

7. Farmers initiating multiple cropping systems may en-counter opposition from the prevalent social, economic,and political system.

8. There is a shortage of trained personnel (technical andscientific) capable of installing and managing multiplecropping systems.

9. There is a general lack of knowledge or understandingof multiple cropping by “decision makers, ” affectingespecially funding for research to make such systemsviable alternatives.

General Resource Use

The most commonly accepted reason ex-plaining why it is possible to obtain betteryields with crop mixtures is that the compo-nent crops differ in their growth requirements.Such combinations of components can be saidto be “complementary” (46).

A mixture makes better overall use of avail-able resources. Negative influences (e. g., com-petition for light, water, or nutrients) betweenthe component members of a successful multi-ple cropping system would be reduced con-siderably. To maximize the advantages of sucha system, it is important to maximize the de-gree to which one component complementsanother. With a greater range of requirementsbetween different elements of the mixture,theoretically the greatest advantages would beachieved.

One way to achieve complementarily is byvarying the crop components temporally—using sequential planting to achieve a multi-ple cropping system that ensures that antag-onistic interactions between the componentsare avoided, Following a crop with another thathas different growth requirements wouldenable the maximum use of resources. Thisconcept has been used for a long time and isthe basic rationale behind crop rotations.

The most advantageous use of soil, for ex-ample, would be to follow one crop withanother that requires different soil nutrients.A subsequent crop would thus be able to ab-sorb fertilizer residues left over from the pre-vious crop, thus reducing the need for fertilizerapplications. For the Eastern United States, ithas been concluded (31) that double croppingsystems such as soybeans after wheat or bar-ley, or the production of silage crops after graincorn or sorghum, can function well,

Depending on the length of the growingseason, numerous sequential plantings can takeplace during a single year. Such systems re-quire special management, with timely harvest,use of proper varieties, alteration of the stand-

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ard planting distance, special selection of her-bicides so as to not create antagonisms or re-sidual effects, and also the possibility of usingno-tillage planting with certain of the rowcrops.

Another form of complementing differentcrop components is through an intensificationof the sequential cropping system known asrelay planting. The same avoidance of overlap-ping plant growth requirements is gained, aswell as the avoidance of direct plant inter-ference, by planting a second crop after thefirst one has completed the major part of itsdevelopment, but before harvest. Relatively lit-tle research on relay cropping has been donein the United States, and most has demon-strated little if any yield advantage (31). On theother hand, in Mexico and Latin America in-numerable examples of relay planting with def-inite yield advantages have been reported,especially for corn and beans (35,39).

Again, the important, and as yet little stud-ied, aspect of relay planting success dependson the correct combinations of timing and va-rieties so as to avoid shading, nutrient competi-tion, or inhibition brought about by toxicityproduced by the decomposition of a previouscrop residue.

Finally, maximum complementarily can beachieved by growing two or more crops simul-taneously, either in rows, strips, or mixed, buttaking advantage of the spatial arrangement ofthe different crops and knowledge of their in-dividual growth requirements. Again, most ex-amples of such systems come from outside theUnited States. One particularly well-docu-mented example is a traditional corn, bean, andsquash system in Tabasco, Mexico (4].

Corn is planted at a density of 50,000 plants/ha, climbing beans in the same hole at a den-sity of 40,000 plants/ha, and the squash inter-mixed among the rows of corn and beans ata density of 3,330 plants/ha. All are planted atthe same time in this case. Beans begin tomature first, using the corn stalks for support;the corn matures second; the squash is the lastto mature. Aerial space is divided such that

corn occupies the upper canopy, beans themiddle, and squash covers the ground. Betterweed control is achieved, and insect pests arelargely controlled by natural enemies. Cornyield was significantly higher for the polycul-ture as compared to different densities ofmonoculture, but beans and squash suffereda distinct yield reduction (table 5). Interest-ingly, the LER (Land Equipment Ratio) valueof 1.73 tells us that the sum of the yields in themixture can only be equaled in monocultureby planting 1.73 times the area divided propor-tionally among the three sole crops,

Table 5.–Yields of Corn, Beans, and Squash (kg/ha)Planted in Polyculture as Compared to Low and High

Densities of Each Crop in Monoculture

Total grain or fruit yields

Crop Monoculture Polyculture

Corn:Density ... , 33,300 40,000 66,600 100,000 50,000Yield . . . . . . 990 1,150 1,230 1,170 1,720

Beans:Density . . . . 56,800 64,000 100,000 133,200 40,000Yield . . . . . . 425 740 610 695 110

Squash:Density . . . . 1,200 1,875 7,500 30,000 3,330Yield . . . . . . 15 250 430 225 80

Crop Total biomass dry weight

Corn . . . . . . . . 2,822.9 3,119.

4 4,477,5 4,870.9 5,927.2Beans . . . . . . . 852.9 895.1 842.6 1,390.4 253.1Squash . . . . . . 240.9 940.9 1,254.0 801.9 478.3

Total Polyculture Biomass 6,658.6

LER (Land Equipment Ratio) = Sum of yields of each polyculture

Sum of highest yield eachmonoculture

LER = 1,720 + 110 + 801,230 7 4 0 4 3 0

LER = 1.73SOURCE Amador, 1980 (13)

The advantage of producing a greater yieldaltogether on less land is obvious. The muchhigher total yield of biomass in the mixture isalso important because much of this organicmatter is returned to the soil, bringing impor-tant consequences in soil fertility, humidityconservation, microbial activity, etc., all relatedto the success of the following crops, Currently,

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studies are being conducted to determine if thehigher yields are the result of more efficientresource use, or if in fact some mutually ben-eficial effect between crop components is tak-ing place, for example, the bean producing ni-trogen that the corn can absorb (12). Thisexample demonstrates the enormous potentialthat multiple cropping systems offer for thefuture.

Specific Resource Use, Conservation,and Management

An intensified land-use system of agriculturewill certainly put greater pressures on the avail-able natural resources of our crop and range-lands. Considerable discussion has focused onthe harmful or beneficial aspects of this inten-sification, and a review of some of the moreimportant aspects can aid greatly in under-standing this problem:

1) Microclimate and Light: In any agroeco-system, a very important aspect of productivityis related to the amount of light converteddirectly to carbohydrate, hence to vegetativematerial, through photosynthesis. Each crop-ping system has a photosynthetic potential,based on its capacity of conversion (2). Mono-culture, especially of annuals, generally havea lower potential because either the plant coveris not complete, or the soil is occupied onlyduring one short season, leaving the surfacebare of photosynthetic capacity until the nextcrop is planted. Light is not like other re-sources, where a reservoir exists and the plantstap it as the need arises, Rather, it has to beused when it is available, thus leaf area be-comes a very important factor. A multi-layeredpolyculture would be able to capture muchmore light energy, raising efficiency, and po-tentially, production.

Apart from the quantity of light absorbed, itsquality is also important. Light that has passedthrough a leaf layer is altered as certain lightwaves are absorbed and others penetrate.Plants in the lower layers of the canopy needto be adapted to this alteration—an aspect wellstudied only in natural vegetation (7). For crop-

ping systems, light has been studied in detailonly for monoculture systems (2) from the pointof view of increasing effective photosyntheticleaf area for the single crop, By manipulatingspecies with different light requirements,greater photosynthetic potential can be achieved.This is made easier by using dominant speciesin the polyculture that do not develop a closedcanopy, allowing considerable penetration tothe next levels. The most shade-tolerant plantsshould be in the lowest levels. In such a sys-tem, the soil surface is in essence completelycovered by plants. This manipulation of plantarchitecture has been studied in detail ecologi-cally (28) and has considerable application inmultiple cropping systems.

Other aspects of the crop microclimate arealso affected. Crops in the lower layers wouldbe subject to less water stress, but care mustbe taken that root system competition for waterdoes not become a problem. Water loss by soilsurface evaporation could be reduced, but tran-spiration from leaf surfaces might be increasedin the crop mixture. Soil temperatures wouldbe lowered, an advantage especially in warmerand drier environments, aiding in the conser-vation and buildup of organic matter in the soil.Protection from wind would be provided forthe lower canopy species. Care would need tobe taken that the increased humidity in thelower canopies does not promote higher in-cidence of certain diseases, especially fungi,either of the roots or foilage.

2. Soil-Plant Relations in Multiple CroppingSystems: Any time that we try to combine twoor more crops simultaneously in one area,there exists the possibility for complex interac-tions between the plants and their soil environ-ment (39). When total complementarily isachieved, the roots of the component speciesoccupy different soil horizons, reducing con-siderably the potential competition betweenspecies and increasing the efficiency of totalnutrient uptake. In combinations of deep-rooted with shallow-rooted species, especiallywhen trees are planted with grasses or annualcrops, the trees are capable of absorbing un-captured nutrients as they are leached into the

76

soil. Then, through their transport to foliage,they can be deposited on the soil surface againas the leaves drop (47).

Intercropping systems have been shown toextract more nutrients from the soil than dosingle crop plantings per unit area of land. Ina very complete study with corn and pigeonpeas in Trinidad (19) (table 6), various param-eters of crop response were measured. Thehighest single crop yields of grain were ob-tained in monoculture, but by adding yieldsof two crops planted mixed or in intercroppedrows, Relative Yield Totals (RYT) were higher.Total dry matter production was higher in themixtures as well. The most interesting aspectis the uptake of nutrients (N, P, K, Ca, and Mg).The total uptake is based on the sum of the twocrops together, and in all cases the total nutri-ent content of the dry matter production washigher for the mixtures, demonstrating thegreater extractive capacity of the multiple crop-ping system. Apparently, for corn and pigeon

peas, row intercropping gave the best results,demonstrating that at times two crops togethercan negatively influence each other, but thetotal yield makes up for the reduction. Eachcrop mixture needs to be examined in detail.

The greater uptake of nutrients in crop mix-tures could deplete the soil more rapidly. Butan aspect of multiple cropping that needs tobe considered is what proportion of this nu-trient content is removed from the system withthe harvest, as compared to the part reincor-porated back into the system. In table 7, acorn/bean polyculture is compared to a cornmonoculture. Total biomass production, aswell as yield removed from the system, is con-siderably higher from the mixture (10,24 tons/ha versus 6.68 tons/ha total biomass). The per-centage of this total that leaves the system isslightly lower for the mixture (61 percentversus 66 percent), but the actual amount oforganic matter returned to the soil in the poly-culture (3.98 tons/ha) as compared to the sole

Table 6.—Effects of Mixed and Row Intercropping on Yields and Nutrient Uptake of Corn (C) and Pigeon Peas(PP) in St. Augustine, Trinidad, Expressed as Relative Yield Totals (RYT)

Sole crop Mixed intercrop Row intercrop

Parameter c PP c PP RYT C PP RYT

Grain yields (tons/ha) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 1.9 2.0 1.7 1.54 2.6 1.8 1,78Total Dry Matter (tons/ha) . . . . . . . . . . . . . . . . . . . . . . . . 6.4 5.1 4.2 3.8 1.40 5.0 4.9 1.74N uptake (kg/ha) . . . . . . . . . . . . . . . . . . . . . ...........-66.0 119.0 48.0 100.0 1.56 54.0 127.0 1.88P uptake (kg/ha). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.0 6.0 9.0 5.0 1.52 11.0 7.0 2.01K uptake (kg/ha). . . . . . . . . . . . . . . . . . . . . . ............51.0 37.0 37.0 32.0 1.59 46.0 33.0 1.79Ca uptake (kg/ha). . . . . . . . . . . . . . . . . . . . . . ...........10.0 22.0 10.0 15.0 1.68 9.0 19.0 1.76Mg uptake (kg/ha) . . . . . . . . . . . . . . . . . . . . . ...........12.0 14.0 9.0 8.0 1.32 9.0 12.0 1.61

SOURCE’ Adapted from Data, 1974, (19), cited by Sanchez, 1976, (39)

Table 7.—Biomass Distribution (in tons/ha) of Dry Matter in a Corn/Bean Polycultureas Compared to a Corn Monoculture, in Tacotalpa, Tabasco, Mexico

Leaves (B) (B) (A)-(B)and (A) Removed (A) Total

Crop Roots Crown stem G r a i na T o t a l matter percent reincorporated

Corn 0.49 0.60 2.29 4.76 b

plus 10.24 6.26 61 % 3.98Beans 0.15 0.00 0.45 1.50b

CornAlone 0.34 0.41 1.57 4.36 b 6.68 4.36 65 % 2.32aWeight of grain of corn is unhusked, including cob and husk, in the manner that the harvest iS removed from the field inthis region.

bIndlcates the removed portion of the biomass.SOURCE: Adapted from Gliessman and Amador, 1979 (24)

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crop (2.32 tons/ha) demonstrates that althoughmore material is produced by the intercrop sys-tem, a greater amount returns to this system.This possibly offsets any increase in extractionof soil nutrients and permits the long-termmanagement of the system.

Another way to increase the return of nutri-ents to the system is to plant “nurse plants. ”These plants do not contribute directly to thebiomass harvested and removed from the sys-tem, but their capacity to capture nutrients andcontinually recycle them in the soil would bean advantage. Local farmers in Tabasco, Mex-ico, use this concept in the management ofweeds (14), leaving those that don’t interferewith the crops and removing those that areharmful. This practice also provides a constantcover over the soil and helps maintain bettersoil structure, conserves water, fosters moremicrobial activity, and over the long run, re-quires fewer chemical fertilizers. By includingplants that “trap” nutrients, such as legumes,such benefits can be improved even more. Thewidespread use of legume trees for shade incoffee and cocoa plantations is a classic exam-ple (27).

3. Water Use in Multiple Cropping Systems:Any discussion of water use should considerrooting patterns. In multiple cropping systems,especially with several crops with differentlyarrayed root systems, a greater volume of thesoil typically is occupied and thus water useefficiency is higher. This is useful, on the onehand, in areas where water supplies are lim-ited. It also helps make more complete use ofcostly irrigation water. It has been proposedthat cover crops in orchards stimulate deeperrooting by the trees (10). Different peak peri-ods of water use in the crop mixtures wouldavoid competition and increase overall wateruse efficiency (8). A crop such as corn that usesrelatively little water in its early stages of de-velopment could be interplanted with an earlymaturing crop that could take advantage of theunused moisture (30).

In areas where water is severely limited, caremust be taken not to plant crops with over-lapping water requirements because in dry

years one member of the mixture could be out-competed by the other (36). Combining twocrops with slightly overlapping water needs,on the other hand, could be used to an advan-tage in areas with widely fluctuating rainfallregimes. In a dry year, one component wouldbe favored, and in a wet year the other, guar-anteeing profitable harvests of at least one cropevery year. Studies on water availability in eachregion, coupled with studies of water needs ofeach component crop of multiple cropping sys-tems, are critical for proper management.

The important effects of multiple croppingon the conservation of water and soil are pri-marily achieved through the maintenance ofa more complete vegetative cover over the soil(26,40). It is important to remember that apartfrom improving cover while the crop is grow-ing, multiple cropping systems aim towardmaintaining this cover between harvests. Thisis achieved by reducing the time betweenharvest and replanting in sequential systems,planting a new crop into another in relay crop-ping, and continually interplanting in an inter-cropped system. The use of trees, either aswindbreaks, for soil stabilization on erodedhillsides, or in areas subject to desertification,can be enhanced greatly by combining themwith crops or pasture grasses (see discussionon Agroforestry).

In summary, although it appears that multi-ple cropping systems use more water, theirability to obtain water not available to mono-culture, use the water more efficiently, andcontribute significantly to soil conservation,demonstrate a further potential for their morewidespread use.

4. Pest, Disease, and Weed Relations: As dis-cussed, possibilities exist for multiple croppingsystems to be both advantageous and disadvan-tageous in relation to problems of pests, dis-eases, and weeds (29,32). The problem has todo with the great complexity of environmentalfactors and their dynamic interactions withinthe cropping systems. Where capital is notavailable or technical assistance has not beenaccepted, we observe that the main means ofpest, disease, and weed control is through bio-

78—

logical control, and through the managementof a great diversity of cropping patterns, bothin time and space (23).

It has been suggested that multiple croppingsystems permit such a control because they aremuch less subject to attack (6,29,38). Thiscomes about because the mixed cropping sys-tem: 1) prevents spread of diseases and pestsby separating susceptible plants; 2) one speciessometimes serves as a trap crop, protecting theothers; 3) associated species sometimes serveas a repellant of the pest or disease to whichthe other crops are subject; and 4) a greaterabundance of natural predators or parasites ofpests are present due to a higher diversity ofadequate microsites and alternate prey.

However, there are also reasons why a multi-ple cropping system may be more susceptibleto attack: 1) reduced cultivation and greatershading due to the presence of associated spe-cies, 2) associated crops serve as alternatehosts, and 3) crop residues from one crop mayserve as a source of inoculum for the others.All of these advantages and disadvantages canexist, and further study is necessary to achievethe combinations that give the most positiveresults.

A few examples might serve to demonstratethe potential of multiple cropping for biologi-cal control. In one study (22), it was shown thatthe planting of a locally used medicinal herb(Chenodium ambrosioides) in sequence withcorn or beans reduced the incidence of nema-tode populations in the soil, demonstrating apotential for reducing attack on the roots of thefood crops, The herb added substances toxicto the nematodes into the soil. In another study,yields of cotton untreated with insecticides, butinterplanted with sorghum, were 24 percenthigher than sprayed monoculture. The reasonwas that sorghum served as a microhabitat forcotton bollworm predators (18). In anothercase, fall army worms were less a problem oncorn associated with bush beans than on pure-stand corn (21). Beans intercropped with cornwere attacked less by rust compared to beansin pure stands, probably because corn func-

tions as a barrier to the dissemination of thefungal spores (41).

Weeds, on the other hand, present anotherproblem. It has been reported that weeds aremuch less a problem in multiple cropping sys-tems, especially in intercropping (32), becausethe space normally available to weeds is filledwith other crops, The aggressive nature ofweeds is well known (9), but recent work hasbegun to show that weeds can fill an impor-tant ecological role in cropping systems, bycapturing unused nutrients, protecting the soil,altering soil fauna and flora, serving as trapplants for pests and disease, and changing themicrohabitat to allow for high populations ofpest predators and parasites (3,17). In ruraltropical Mexico, farmers understand and usea “non-weed” concept (14), where each isclassified according to positive or negative ef-fects. We need to understand in more detail thebiological functions of each component of theagroecosystem to establish the structure thatwill allow adequate weed, pest, and diseasecontrol, If part of this control can be achievedby merely manipulating the crop mixture intime and space, great strides toward more ef-ficient agricultural management can be made.

5. Mutualisms and Crop Coexistence: In nat-ural ecosystems, a great number of interactionsbetween different species are mutually bene-ficial for those organisms involved, leading usto believe that there is a strong selective pres-sure operating to select combinations thatcoexist rather than compete (37). On the longterm, such a coexistence permits a more effi-cient use of resources, with the componentorganisms aiding one another rather than in-teracting negatively. This frees more energy forgrowth and reproduction.

To a certain extent, nurse crops or compan-ion plants function in this way. Legumes, be-cause of their symbiosis with nitrogen-fixingbacteria, can coexist with corn without com-peting for nitrogen. In fact, part of the legume’snitrogen may be available for the corn (12), re-ducing overall need for fertilizers. Studies withcoffee and cocoa shade trees have demon-

79

strated the same relationship; the trees provideshade, nitrogen, and an organic mulch over thesoil.

As mentioned, the presence of one crop mayhave beneficial effects on others through altera-tion in the microclimate, pest and disease pro-tection, etc. Thus, apart from looking for cropsthat complement one another by avoidingoverlap in requirements, we need also to lookfor crops that are interdependent and thatmutually benefit from the association, This willbe a very stimulating challenge for crop selec-tion programs.

6. Use of Space and Time: One of the mostimportant aspects of the management of multi-ple cropping systems is the facility they offerfor the intensification of production throughmanipulation of space and time. By achievingthe most ideal combination of the two, we willachieve the greatest productivity. On the onehand, we attempt to occupy the available re-source space as efficiently as possible, combin-ing species that complement each other, yet at-tempting to avoid overlaps that lead to negativeinteractions.

Resource use in space is then combined withits use in time, trying to achieve constant useof the resources available. For this reason,multiple cropping systems are intensified bysequential, relay, and mixed planting thatestablish constant resource use within the envi-ronmental limits imposed by the ecologicalconditions of each region. In this sense, we caneven visualize the possibility of including coldresistant trees in association with annual cropsor pasture, so that during the winter the treescontinue to occupy the area. Thus, any yieldreduction during the normal frost-free grow-ing season is compensated for by the long-termtree production,

Additionally, multiple cropping systems per-mit greater stability in production, despitevariability in climate or physical factors in theplanting area. Whatever the conditions in onelocation and for one growing season, at leastone member of the multiple cropping systemwill succeed. Since most of the better drainedand structured soils are already in production,

the more marginal lands will require specialtechnology to make them produce. We cannotconsider for the moment massive programs ofsoil and water manipulation needed to installmechanized high-yielding monoculture, To doso is economically, if not ecologically, pro-hibitive. The basic framework is available inmultiple cropping, Innovative combinationsneed to be searched for and tested.

Agroforestry: A Multiple CroppingSystem

Agroforestry is a technology of land manage-ment that combines trees with agriculturalcrops, with animals, or any combination of thetwo. Combinations can be simultaneous, orstaggered in either time and space. The majorobjective of agroforestry is to optimize produc-tion for each unit of surface area, keeping inmind the need to maintain long-term yield(11,13,42). Small-scale, traditional agriculturehas always included trees as integrated ele-ments of farm management, but only recentlyhas interest been revitalized in the applicationof agroforestry practices into modern agri-culture.

The renewal of interest in agroforestry isbased on many of the same reasons for multi-ple cropping systems in general: the ever-increasing demand for production, yet the ris-ing cost of obtaining it. The explosive demandfor firewood and lumber has placed incredi-ble pressures on the world’s forests, especiallyin tropical and subtropical regions. Deforesta-tion continues at an accelerated rate (20,44).But programs of reforestation or multiple-useforest management do not satisfy basic needsfor food, clothing, and other necessities thatcome from crop and range lands. It wouldseem logical that these pressures for both for-est and agricultural products would stimulatetheir combination in agroforestry systems.

Agroforestry practices can be broadly clas-sified into three types (15): 1) combined agro-silvicultural (crop plus trees) systems, 2) com-bined forestry and grazing, and 3) simultaneouscombinations of forestry with crops and graz-ing. Examples of each of these classifications

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are presented in table 8. The focus varies fromsoil improvement, erosion control, wind breaks,and shade to lumber, firewood, and reforesta-tion. The combinations are essentially unlim-ited, depending on the needs of each region.At first glance it might appear that agroforestrysystems are most applicable on marginal lands,on steep slopes, poor soils, or areas with widelyfluctuating rainfall regimes. But agroforestryshould also be considered for widespread ap-plication, even on prime agricultural or graz-ing land, because production needs to be in-creased—both by opening up new areas and bylooking for innovative ways to increase produc-tivity of lands already in use.

The principle limitations to widespread useof agroforestry practices are economic andtechnological. Ecologically, the advantages arewell known, but technically we still do not havethe information necessary to begin immediateimplementation. With the present focus in agri-culture aimed at maximizing single crop yields,there is a lack of acceptance of the idea thatyields need to be thought of more on a long-term, diversified basis. Agricultural researchhas not yet accepted the challenge that an in-tegrated focus to forest and farm managementrequires.

Socioeconomic Implications ofMultiple Cropping Systems:Perspectives for the Future

In all of the aspects of multiple cropping sys-tems that this review has considered—yield, re-source use, pest and disease control, weeds,use of space and time, types of planting sys-tems—much of the evidence indicates thatgenerally there are more advantages than dis-advantages of a biological, physical, or agro-nomic nature. But we need to consider thesocial and economic implications of the pos-sible more widespread use of multiple croppingsystems in present day agriculture.

As was seen in table 4, the types of advan-tages derived from multiple cropping are manyand varied. With a greater diversity of crops,

Table 8.—Classification and Examples of AgroforestryTechnologies

Combined agrosllvicultural systems (trees with crops):1. Agrosilviculture— establishment of trees, intercropped

with agricultural crops during initial stages of tree growth,until tree canopies close and force the elimination of thecrops. Production available in early stages of tree develop-ment, and cultivation activities simultaneously benefit bothcrops and trees.

2. Forest trees of commercial value in crop systems. Main-tain trees in crop areas, either planted or natural, at lowdensities that do not interfere, yet provide value in thefuture.

3. Fruit trees in crop systems. A system that allows fruit pro-duction and grain or vegetable production simultaneously.

4. Trees that serve as shade for certain crops or improve thesoil through nitrogen fixation, organic matter incorpora-tion, mulch, and microclimate modification.

5. Trees used as hedgerows, fence lines, or windbreaksaround cropping areas, where management is intimatelylinked with the needs of the crops.

6. Trees around rivers, lakes, or artificial reservoirs or tanks,integrated with fish or waterfowl management, providingshade, food, and roosting.

Combined forestry and grazing systems (trees with grasses):1. Grazing or forage production takes place within forestry

plantations, aiding in avoiding weed or brush build up,lowering fire risk.

2. Grazing or forage production in young natural forests, withsame advantages as above.

3. Forest trees of commercial value in pastures, either plantedor natural, at densities that do not interfere with the pasturespecies.

4. Timber trees in pasture, either planted or natural, with thecapacity to fix nitrogen and improve soil, thus lowering theneed to fertilize and provide commercial value.

5. Trees in pastures that provide shade for the animals andaid in improving the soil through nitrogen fixation andnutrient extraction from deeper soil levels.

6. Trees, either in or around pastures, or in forests, that pro-duce foliage of forage value for animal consumption. Canallow the reduction of feed supplement for animals.

7. Fruit trees in pastures, allowing for commercial produc-tion of both fruits and animals.

8. Trees around pastures as hedgerows, fence lines, or wind-breaks.

Simultaneous combinations of forestry with cropsand grazing:1.

2.

3.

—

Forest plantations planted with crops and grasses, permit-ting the management of grazing animals, either free towander or enclosed in specific areas. Especially adaptedto smaller animals, such as ducks or pigs. Requires closecontrol of activities and use of specific crops.Trees associated with crops and grazing, either planted ornatural, in densities that will not adversely influence thecrops. Trees scattered in and around cropping areas canbe periodically pruned and used as forage for animals, withthe timber harvestable at some later date.Hedgerows or living fence lines around rural communities,serving as shade, windbreak, property divisions, forage,fruits, timber, and firewood. In this sense, the system istruly multiple use.

SOURCE: Combe and Budowski, 1979 (15)

81

a farmer is less affected by market fluctuationsand is able to shift from one crop to anotherdepending on price and demand, At the sametime, the harvest is spread out over a longerperiod of time. Less dependence on outsideenergy sources has obvious advantages, espe-cially in areas where capital is limited. Labor,instead of being concentrated in certain peri-ods of the year, can be more evenly distributed,an important consideration in relation to themigrant farm worker problem. In times ofhigher unemployment, multiple cropping sys-tems can offer more and steadier work.

Most of the economic disadvantages arederived from our lack of experience and knowl-edge with multiple cropping systems. Reportedlower yields, complexity of management activ-ities, higher labor demands, and the difficultyin mechanizing such systems are all importantfactors that discourage modern farmers fromparticipating in multiple cropping practices.

An important aspect of this resistance comesfrom the emphasis on large profits that governsso much of modern agriculture today. Maxi-mum profits in the short term, rather than con-cern with maintaining constant income in thelong term, governs the decisionmaking proc-ess on most American farms today, But withthe incredible rise in farm costs, a new focusis necessary. All of these increases cannot bepassed onto the consumer. Many of the advan-tages of multiple cropping systems definitelyneed to be stressed more for use on farmstoday. Smaller farms, with a greater diversityof products and activities, can function quite

profitably because they are less dependent onhigh-cost energy inputs. Lower costs meanfood can be produced at a lower price, the ben-efits being transferred to the general popu-lation,

Smaller farms would require more farmers,To a certain extent multiple cropping systemsmean a return to the land, with the incentivesnecessary to keep the farmers there. The greatdiversity of activities in multiple cropping sys-tems would promote an increase in interdis-ciplinary activities in their investigation,installation, management, and use in agricul-ture. This stimulation of interchange andcollaboration can, in the long term, lead togreater social cohesion, Rural regions mightonce again take on the social importance theyenjoyed in the past. The problems of lack oftrained personnel, and social, political, andeconomic restrictions on multiple croppingsystems, all can be overcome by thorough andconscientious programs of research aimed atdetermining the proper methods, varieties, andpractices necessary.

The belief that multiple cropping is only suit-able for marginal or underdeveloped regionsignores the fact that just a relatively short timeago, such systems were the most common typeof agriculture. Only recently have they beenreplaced by monoculture systems dependenton the use of massive quantities of inexpensivehigh energy inputs. For the moment, this timehas passed and we need to learn from the pastto reshape agriculture for the future. This willbe a great challenge for agricultural research.

82

1,

2.

3.

4.

5.

6.

7.

8

9

10.

11.

12.

13.

14.

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, .,

Chapter VI

Development of Low Waterand Low Nitrogen Requiring

Plant Ecosystems for AridLand Developing Countries

Peter FelkerDepartment of Soil and Environmental Sciences

University of CaliforniaRiverside, CA 92521

Page

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87Beneficial Aspects of Semiarid Plant Production Technologies on Semiarid

Developing Countries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88Where Technology is Used and Stage of Development

(Subsistence, Commercial, or Research) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89Development of Tree Legumes for Fuelwood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89Use of Nitrogen Fixing Trees to Increase Soil Fertility. . . . . . . . . . . . . . . . . . . . . 89Development of Cash Crops on Semiarid Lands . . . . . . . . . . . . . . . . . . . . . . . . . . 90Production of Livestock Food and Forage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91Intercropping Traditional Food Staples With Arid-Adapted Legumes to

Sustain High Food Staple Yields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92Slowing the Spread of Desertification in Arid Regions . . . . . . . . . . . . . . . . . . . . . 93

Fertilizer, Pesticide, Irrigation, and Machinery Requirements . . . . . . . . . . . . . . . . . . 93Irrigation Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93Fertilizer Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93Pesticide Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94Machinery Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

Research, Development, and Implementation of Arid-AdaptedPlant Ecosystem Production Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

Constraints Facing Development and Implementation of Arid-AdaptedPlant Production Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Effect of Technology Implementation on Capital, Labor, andLand Requirements.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Impact of Wide-Scale Technology Implementation on the SocioeconomicStructure of Agriculture in Developing Countries.. . . . . . . . . . . . . . . . . . . . . . . . . . 100

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101Work Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

Table

Table No. Page

l. Outline of Research Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

Development of LowNitrogen Requiring Plant

Chapter VI

Water andEcosystems

for Arid Land Developing Countries

This paper describes a low industrial input,commodity-oriented approach to stimulatingeconomies of arid land countries using arid-adapted plant species. It suggests legume treebiomass farms using Acacia, Leucaena, andProsopis genera to provide increased fuelwood.Increased soil fertility and ensuing water useefficiency could be achieved by using deeplyrooted, drought-adapted species such as Acaciaalbida and Prosopis cineraria that fix nitrogen.Arid-adapted shrubs such as jojoba (Simmond-sia chinensis), and guayule (Parthenium argen-tatum) could provide stable production of cashcrops. Prosopis and Acacia pods, atriplex for-age, Leucaena forage, and cactus pads couldincrease livestock food supplies, Increased pro-duction of traditional food staples such as mil-let, sorghum and peanuts can be achieved byintercropping them with arid-adapted legumes.Aggressive management of these plants couldhelp reduce the spread of desertification.

Little government support has been madeavailable for these activities despite their wide-spread use by indigenous farmers at subsis-tence levels. A research and development pro-gram is suggested that would establish living

germplasm collections and select and propa-gate superior clones, Several months afterstand establishment, these plant systems canbe grown without supplemental irrigation byusing ground water within 10 m of the surfaceor by using a minimum of 250 mm annual rain-fall. Phosphate fertilizer, micronutrients, andrhizobial inoculation are required, but the ni-trogen needs will be provided by nitrogen fix-ing plants. Less machinery will be needed totill these systems.

Wide-scale implementation of these systemswould greatly enhance agricultural produc-tivity at the local level, where it is most needed,and indirectly stimulate nonagricultural sec-tors of the economy. The increased economicwell-being of farming classes could lead to de-creased political unrest and greater stability ofgovernments in arid lands, Foreign policy ef-forts to strengthen the peace by buildup of mil-itary hardware systems has proven futile inEthiopia, Iran, and Iraq. Development of aridland plant production systems is a viable alter-native to enhancing peace in politically volatilearid land countries.

INTRODUCTION

This document was prepared at the request follows OTA’s specific issues and questions.of the Office of Technology Assessment (OTA) For the convenience of the reader, these re-of the U.S. Congress to provide guidance in de- quests are reproduced in appendix A.velopment of low energy, nitrogen, and ma-chinery requiring agricultural systems for semi- Identifying plant physiological, morpholog-arid developing countries, The format closely ical, and ecological characters that lend them-

87

88

selves to a minimal machinery, capital, andfossil fuel input is the subject of a paper byFelker and Bandurski (14) in which orchardsof leguminous trees were suggested to mostclosely approximate an ideal system for mini-mizing industrial inputs. Other closely relatedshrub ecosystems have been suggested toachieve similar objectives (32). Identificationof arid land plant species that would lead tomore stable and productive ecosystems has

been intensively investigated by Felger (11). Re-cent review volumes (42) and symposia (27,6)have dealt at length with arid land plant re-sources. This document attempts to synthesizethe knowledge of arid land plant species, focus-ing on minimal energy input agriculture anda pragmatic commodity-oriented approach de-signed to provide major needs such as fuel, for-age, and food staples required for arid landeconomies.

BENEFICIAL ASPECTS OF SEMIARID PLANT PRODUCTIONTECHNOLOGY ON SIMIARID DEVELOPING COUNTRIES

Development of leguminous trees (14) andassociated semiarid ecosystem plant compo-nents such as saltbush (A triplex spp.) (19), leu-caena (Leucaena leucocephala) (15), cactus(Opuntia and Cereus spp.) (33,52), jojoba (Sim-mondsia chinensis) (23), and guayule (Par-thenium argentatum) (50) can make a significantcontribution to meeting the major commodityneeds of people in semiarid developing coun-tries. Some of the main biological needs andappropriate approaches to supplying them areas follows:

1. Need: increased availability of inexpen-sive fuelwood.Approach: use of leguminous tree biomassfarms with Prosopis, Leucaena, a n dAcacia species.

2. Need: increased soil fertility to triple orquadruple water use efficiencies of foodstaples so that productivity is water-limitedand not fertility-limited.Approach: use locally respected, drought-adapted, nitrogen-fixing legume tree suchas Acacia albida and Prosopis cineraria,use shrubby legumes such as Dalea spe-cies, and use perennial arid-adapted her-baceous legume such as Zornia a n dTephrosia.

3. Need: production of cash crops forfarmers and for foreign exchange.

4.

5.

6.

Approach: use perennial arid-adaptedplants, such as jojoba, guayule and highvalue, drought-adapted annuals, and ephem-erals, such as sesame when grown in con-junction or rotation with arid-adapted ni-trogen fixers.Need: production of livestock food andforage.Approach: use arid-adapted, salt-tolerantshrubs, such as saltbush (Atriplex species)in conjunction with high water to dry mat-ter conversion plant specialists, such asspineless cactus (Opuntia ficus-indica) andhigh protein and/or sugar content pods ofleguminous tree species of Acacia tortilis,Acacia albida, and Prosopis spp.Need: sustained production of traditionalfood staples, such as millet, sorghum,groundnuts, and cowpeas.Approach: intercrop the annual stapleswith nitrogen fixing trees previously dem-onstrated to stimulate annual legumeyields such as the association with Acaciaalbida and peanuts.Need: slow the spread of desertification.Approach: when intensive managementof forage, fuelwood, and staple productsare carried out as outlined above, desertifi-cation will slow.

89

WHERE TECHNOLOGY IS USED AND STAGE OF DEVELOPMENT(SUBSISTENCE, COMMERCIAL, OR RESEARCH)

Development of Tree Legumesfor Fuelwood

Areas of use: Prosopis alba and P. nigra werereported to have fired industrial boilers andsteam locomotives during World War II inArgentina (10). In Chile, the leguminous treeschanar (Geoffrea decorticans) and espino(Acacia caven) have been widely harvested byIndians and present day subsistence farmersfor fuel (2). Mesquite wood and charcoal (Pro-sopis species) is highly esteemed and widelyused in the Southwestern United States insteakhouses for barbecues and home heating,From 1956 to 1965, 78,000 metric tons of mes-quite charcoal and 200,000 m3 of mesquitefirewood were recorded as items of commercein Mexico (29), In the Jodphur state of India,Prosopis was declared the “royal plant” be-cause it provided the bulk of the fuel to the localpopulation (20). Acacia forests are harvestedalong the Nile 400 km upstream from Khar-toum, Sudan, and brought to Khartoum forbrick making and other industrial uses (24). Inthe Sahelian zones of Africa, many of theAcacia species such as A. tortilis, A. seyal, andA, senegal are consumed for woody biofuel.

Research organizations: The Central AridZone Research Institute in Jodphur has beenconducting research on leguminous trees assources of biofuels since the early 1940s (1),Their work is meagerly documented in thescientific literature and, from the lack of recentpapers in the literature, their current researchon tree legumes does not appear to be veryactive.

The Forestry Research Institute in Khartoum,Sudan, has received about $200,000 from theInternational Development Research Center(Ottawa) to evaluate Prosopis species under200, 300, and 400 mm annual rainfall regimes.Much of the seed material for this experimentwas supplied by the University of California-Riverside mesquite project. The United Na-tions Development Program (UNDP) providedsupport for Felker to supply seeds, mesquite

rhizobia, plants, containers, and consultationto conduct varietal trials with 30 selections ofleguminous trees (most Prosopis) in the Sudanat the Forestry Research Institute, Over 400acres of Prosopis have been planted along ir-rigation canals in the Sudan courtesy of the Su-dan Council of Churches to prevent sand fromblowing into and filling the canals (26).

Dr. J. Brewbaker at the University of Hawaiihas been conducting extensive research in Ha-waii, Colombia, and the Philippines, on the de-velopment of leucaena as a biofuel crop. In theUnited States, the U.S. Department of Energyhas funded research on Prosopis under Felkerat the University of California-Riverside to de-velop an arid-adapted germplasm collection;to evaluate the collections in field conditionsunder drought, heat, and frost stress; to studynitrogen fixation and salt tolerance; and toclonally propagate outstanding single trees.

Use of Nitrogen Fixing Trees toIncrease Soil Fertility

Areas of use: Prosopis cineraria has beenused on a subsistence level by farmers in theIndia-Pakistan region to increase the yields oftheir pearl millet crops. Soil chemistry studies(46) corroborated increased nutrient contentsand forage yields under P. cineraria t r eesversus other trees and open control areas.Acacia albida is widely used on a subsistencelevel in the West African countries of Senegal,Upper Volta, Mali, Niger, and Chad to increasethe yields of sorghum, millet, and peanutsgrown beneath the tree canopies (12). Parkiabiglobosa was observed by this author grow-ing in sorghum fields in a 400 mm annual rain-fall regime where farmers stated the Parkia alsoincreased the yields of their crops.

Yields of grasses and forbs grown in a growthchamber on soil from beneath mesquite can-opies were four times greater than herbageyields grown on soils from outside mesquitecanopy cover (49). The stimulation of forageyields after mesquite removal in the Southwest-

90

ern United States is probably due to increasesin soil fertility supported by nitrogen fixationand reduction in competition for water. Mes-quite nitrogen fixation and soil fertility in-creases on the 72 million acres (38) presentlyoccupied by mesquite in the SouthwesternUnited States is an unrecognized resource.Leucaena (Leucaena leucocephala) has beenwidely used in the Philippines in rotation withother crops, as a companion crop, and as agreen manure with other crops to increase soilfertility.

Research organizations: Dr. Y. Dommergue,working for ORSTOM in Dakar, Senegal, WestAfrica, has conducted rhizobial inoculationtrials with many African Acacias includingAcacia albida and at this writing is actively in-volved in nitrogen fixation aspects of semiaridsoils. Dr. Habish at the University of Khartoum,Sudan, published excellent papers on char-acterization of Acacia-rhizobia symbioses (21),but is now a dean at the University and nolonger actively involved in research. A Univer-sity of Arizona group, funded by the NationalScience Foundation (NSF), with Dr. Pepper asprincipal investigator, is collecting and char-acterizing rhizobia strains from many arid-adapted legumes.

A three-year $650,000 NSF grant has beenawarded to study nitrogen cycling in a mes-quite dominated desert ecosystem in southernCalifornia. This project involves: 1) an ecologygroup headed by Dr. Philip Rundel at theUniversity of California, Irvine, that is conduct-ing dry matter productivity analyses; 2) aUniversity of California-Riverside soils groupheaded by Dr. Wesley Jarrell, that is convert-ing the dry matter productivity measurementsof the Irvine group into nitrogen productivityand conducting soil moisture profile measure-ments with 20 ft deep neutron probes, quan-titating soil chemical characteristics on andaround the site, quantitating denitrification,and developing in situ acetylene assays; and3) a Washington University (St. Louis) groupheaded by Dr. D. H. Kohl that is correlating theabove-mentioned findings with natural abun-dance 15N 14N measurements to develop quali-

tative and perhaps semiquantitative assays ofnitrogen fixation from dried plant samples,

The Department of Energy has funded studieson cross-inoculation of 13 Prosopis species (15),has conducted greenhouse studies of the effectof heat and drought stress on Prosopis nitro-gen fixation, and has developed models com-paring efficiencies of water and nitrogen in-puts to increasing productivity of semiaridrangelands (16). USDA scientists have demon-strated that fertility can dramatically increasewater use efficiency of rangeland species in alo-year study on Montana rangelands (51). TheUSAID-supported Niftal group at the Univer-sity of Hawaii maintains large stocks ofrhizobia. Basak and Goyal (3) at the CentralArid Zone Research Institute at Jodphur havepublished cross-inoculation data and temper-ature and salinity tolerance characteristics forrhizobia for semiarid adapted leguminous treesin India,

Development of Cash Crops onSemiarid Lands

Areas of use: Jojoba (Simmondsia chinensis),a non-legume, is one of the most promisingcash crops for arid lands. Jojoba seeds containa rancidity-resistant, non-allergenic, liquid waxwith lubricating properties equivalent to an oilobtained from the endangered sperm whale. Jo-joba is under development in southern Califor-nia, Arizona, Mexico, and many of thesemiarid less developed countries (53). Maturejojoba plantations should yield over 1,000 kg/ha 1 at over $1 per kg. This yield could earna gross return of over $1,000 per hectare.

Guayule (Parthenium argentatum) a plantnative to the Chihuahua deserts, contains nat-ural rubber and is under extensive develop-ment by both the United States and Mexicangovernments (50). There is no reason guayulecould not be cultivated in other semiarid re-gions of the world as a cash crop.

Hydrocarbon bearing plants such as Euphor-bia lathyris have been suggested as raw mate-rials for oil and gasoline production (7). The

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drought-adapted legume trees Acacia senegalexudes a gum from wounds of the trunk knownas gum arabic that has many industrial andfood uses (18), Eighty-five percent of theworld’s annual supply of gum arabic, about50,000 to 60,000 metric tons, is harvested andexported from the Sudan at prices of about $1per kg (18), Other Acacia and legume trees,such as Prosopis, exude gums that could be de-veloped for cash crops. Seeds of the fast-growing, drought-tolerant, annual sesame sellfor $1 to $2 per kg and show potential for anarid zone cash crop (53). The fruits of thecactus Opuntia ficus-indica can producedessert or table quality fruits. This author wasserved an excellent cactus fruit with a meal ona Chilean airline. Commercial (5 ha and larger)Opuntia ficus-indica orchards are currentlyoperating in southern California to supplythese fruits to supermarket chains. There areseveral little-known species of cactus thatpossess fruits equal or superior in quality toOpuntia ficus-indica that could also be devel-oped (11). Because cactus use water very effi-ciently, they should support fruit and cash cropproduction in semiarid areas.

The pods of carob (Ceratonia siliqua) are bro-ken into pieces, kibbled, and separated intoseed and pod fractions, The pod fractions aresold for livestock food in Europe and are im-ported into the United States where they aremanufactured into chocolate substitutes (34).Industrial quality gums are extracted from theseeds, In 1970, the world production of carobseed gum was 15,000 tons. Prices ranged from$0,62 to $1,10 per kg (43). The pods of Parkiabiglobosa and P, clappertoniana, and a fer-mented product of the seeds known as dawa-dawa, are sold for human food on the sub-sistence levels in markets in Senegal and otherparts of West Africa.

Research organizations: The most extensivegermplasm collections, plantings, and cytoge-netic studies of jojoba are being made at the Uni-versity of California-Riverside under Dr. D. M,Yermanos. This has been funded by the UnitedNations Development Programme (UNDP),NSF, and the California State Legislature.Another large-scale jojoba research operation

is being carried out at the University of Arizonaunder Dr. L. Hogan. There are numerous com-mercial jojoba developers, some of whom areless than scrupulous. Donor agencies should con-tact Yermanos or Hogan before dealing withprivate jojoba developers, Dr. Yermanos hasalso developed nonshattering sesame types andmechanical harvesting devices with UNDPsupport. The USDA has a multi-million-dollarbudget to develop guayule in the Southwest-ern United States.

The Diamond Shamrock Co. is supporting amulti-million-dollar project at the University ofArizona Office of Arid Land Studies to developpotential of hydrocarbon producing plantssuch as Euphorbia lathyris,

The Canadian International DevelopmentResearch Center (IDRC) is supporting a re-search program to develop gum arabic for WestAfrica through the “Eaux et Foret” in Dakar,Senegal. The University of Chapingo, Mexico,has a program to develop spineless cactus (52),Dr. Richard Felger at the Arizona/Sonora Des-ert Museum has identified numerous arid landcrops with potential including several out-standing cactus varieties.

Production of Livestock Foodand Forage

Areas of use: In Mexico, Prosopis glandulosavar. glandulosa, and Prosopis laevigata areharvested from wild trees and sold to whole-sale dealers who incorporate it into livestockrations. In 1965, 40,000 tons of mesquite podswere sold in commercial operations in Mex-ico (29). Undoubtedly, many more pods wereused or bartered locally that were neverentered into the agricultural statistics. Onethousand ha of P. juliflora has been establishedin the Peruvian coastal desert under partial ir-rigation. By providing 250 mm of irrigation thefirst year and 160 mm thereafter, pod produc-tion of 6 to 7 t/ha- have been obtained fromthe Peruvian plantings (39), In nearby Chile,30-year-old P. tamarugo trees growing in theAtacama salt desert have produced 6,000kg/ha-’ of leaves and pods that are used tosupport a sheep-raising industry (44). Twenty-

38-846 0 - 85 - 4

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two thousand hectares of P. tamarugo havebeen planted by the Chilean corporation CORFO(54). Felker has visited these areas to assistCORFO with vegetative propagation, selectiontechniques, and nitrogen fixing inoculants.

In the Southwestern United States, mesquitepods were the staple for Indians in southernCalifornia and Arizona deserts (13), but todayare only marginally important in supportingwildlife. In West and East Africa the pods ofA. albida and A. tortilis are highly regarded asa supplemental livestock feed (12,34). Some A.albida pods are collected and stored for laterrationing to cattle on a subsistence level, butno organized or commercial use of pods hasbeen attempted (12). The forage of Acacia xan-thophlea and A. hockii supplies much of thediet of giraffes in the Serengetti National Parkin East Africa, Pellew (41) has suggested thatthe Acacia-giraffe ecosystem be managed formeat production,

Forage systems based around the spinelesscactus (Opuntia ficus-indica) have been widelyused in Mexico and North Africa where thespineless pads are fed to cattle. Selections ofsaltbush (A triplex species) are high in proteinand carotenoids and constitute a useful live-stock forage. The Chilean corporation CORFOhas planted thousands of hectares of saltbushin contour ridges along the Chilean coast foruse as cattle food (Felker, personal observa-tion). In Tunisia, commercial-scale, govern-ment-supported plantings of saltbush provideforage for grazing animals (22).

In Mexico, cattle rations have been formu-lated from high energy, sweet, highly palatablemesquite pods; high protein, high carotenoidand low palatability saltbush foliage; and high-energy containing cactus pads (29). These threeplants possess the complimentary physiologi-cal characters of high salt tolerance in saltbush,h i g h w a t e r t o d r y m a t t e r c o n v e r s i o nefficiencies of cactus, and nitrogen fixing prop-erties of mesquite.

Research organizations: Surprisingly littleresearch is being done about these forageplants. The Tunisian and Chilean governmentssupport the largest developments of forage-pro-

ducing plants, The Chilean company CORFOhas planted thousands of hectares of Atriplex.CORFO has investigated plant spacing, canopyclosure, and pod productivity as a function ofage for 36-year-old Prosopis tamarugo planta-tions (44). They are just beginning to becomeinvolved with selection work, nitrogen fixation,and vegetative propagation.

The Tunisian government has employedlarge earth-moving equipment and water trans-port vehicles to establish saltbush and cactusplantings (22). The Algerian government alsohas initiated some Opuntia plantings (33). Dr.Henri LeHouerou, formerly of the Interna-tional Livestock Center (ILCA) in Addis Ababa,has been a key figure in North African devel-opments of Atriplex and Opuntia. The Chap-ingo Agricultural Experiment Station outsideof Mexico City has made selection of Opuntiawith promising economic characters (52).Lopez, et al. (28), at the Antonio Narro Agri-cultural University in Saltillo, Mexico, has con-ducted a thorough analysis of the productivityand ecosystem characteristics of economicallyimportant aspects of Opuntia production inMexico. The International Development Re-search Center, Ottawa, is supporting a Prosopisjuliflora forage production project in Peru.

In the United States, Dr. C. M. McKell, PlantResources, Inc., Salt Lake City, and Dr. J.Goodin of Texas Tech University have con-ducted extensive research on saltbush as aneconomically important forage crop. Felker,while at University of California-Riverside,made Prosopis selections for pod producingcharacteristics in cooperation with Becker andSaunders at the USDA Western Regional Re-search Center. They also have conducted pro-ximate analyses and feeding trials on the pods.

lntercropping Traditional FoodStaples With Arid Adapted LegumesTo Sustain High Food Staple Yields

Areas of use: Prosopis cineraria has beenwidely used in the Indian-Pakistan region ona subsistence level to increase yields of pearlmillet and other forage crops grown beneathits canopy (31). Acacia albida has been used

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in West Africa to increase yields of millet,sorghum, and peanuts (9,8,12). Farmers in the400 mm annual rainfall region of Senegalremarked to this author that Parkia biglobosahad the same fertilizing effect as Acacia albidaon millet and sorghum.

Research organizations: The Frenchoverseas development organization ORSTOMcommissioned soil fertility studies carried outby Dancette and Poulain (9) and Charreau andVidal (8). AID commissioned a state-of-the-artreport on Acacia albida in 1978 (12). FAO sup-ported a nursery scheduled for termination in1978 in Kebemer, Senegal, dedicated to rais-ing enough Acacia albida seedlings to plant1,000 ha per year at 45 trees per hectare. ACARE project in Chad was involved in refor-estation with Acacia albida. No serious fieldstudy has ever been conducted to develop im-

proved genetic stock and management prac-tices for arid-adapted leguminous trees.

Slowing tho Spread of Desertificationin Arid Regions

Little work is being carried out to slow deser-tification. K. O. Khalifa, working for the SudanCouncil of Churches, has planted 400 acres ofProsopis along irrigation canals to prevent thewind from filling them. The Indian govern-ment has been planting shelterbelts with Pro-sopis and other arid adapted trees since the1920s and 1930s (25). No serious efforts em-ploying arid-adapted shock, e.g., Prosopis,Acacia, or Leucaena, and modern forestrypractices have been applied to control of deser-tification in less developed countries.

FERTILIZER, PESTICIDE, IRRIGATION, ANDMACHINERY REQUIREMENTS

Irrigation Requirements

Over 90 percent of the land in semiarid re-gions must rely on rainfall without supplemen-tal irrigation (excluding areas where waterharvesting technologies are possible). All of thedesert-adapted trees, shrubs, and ephemeralsdescribed here have the capability to growwithout irrigation in semiarid zones, If wateris not available, these plants can close stomates,shut down photosynthesis and transpiration,allow their finely divided leaflets to reach airtemperature, and adjust their water potentialsto minus 40 to 50 bars and wait for the nextrain (17). Annuals would wilt and die under thesame conditions.

Reasonable production from reproductivestructures, such as mesquite pods, jojoba nuts,or cactus fruits cannot be expected below 250mm annual rainfall unless they are located inwater drainage areas or areas where water ac-cumulates. Growth of vegetative parts for woodor forage production probably will continuefrom 150 to 250 mm annual rainfall. Deep-

rooted tree and shrub systems are not as sus-ceptible to moisture stress as are shallow-rooted annuals. To get optimal water use, anagroecosystem needs an optimal mix of nitro-gen fixers and water to dry matter conversionspecialists. When it is possible to use cactus,which has a fivefold greater efficiency of con-verting water to dry matter than legumes (17),legumes should not be used to produce theenergy portion of livestock feed. However, leg-ume leaf litter will be required to create goodfertility so the cactus can achieve its maximumwater use efficiency. For the same reason,cactus should not be used to produce the pro-tein and nitrogen needs of livestock when it ispossible to use legumes. Livestock need bothenergy and protein rations and both energy andprotein producing plant specialists are re-quired.

Fertilizer Requirements

A central component of this approach to de-veloping country agriculture is widespread in-

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corporation of arid-adapted, nitrogen fixinglegumes that are capable of fixing nitrogenunder conditions too harsh for temperate leg-umes (e. g., clover, alfalfa, etc.). These legumesrequire no nitrogen themselves and when prop-erly incorporated into a diversified ecosystem,they will reduce nitrogen needs for non-leg-umes as well. Many of these plants, both legu-minous (e. g., mesquite) and non-leguminous(e.g., jojoba) have very deep root systems (13)capable of mining nutrients found in clays,bedrock, and parent materials. Additionally,these deeper rooted shrubs would be expectedto have a higher capture ratio of applied fer-tilizers because they are less likely to allow nu-trients to leach beyond the deep root zone.Also, many of these plants are perennial, andthey would be expected to reduce wind andwater erosion.

Under rainfall as low as 300 mm, it may bedesirable to practice clean cultivation or useherbicides between rows of mesquite, cactus,saltbush, jojoba, and guayule to increase waterinfiltration and to reduce water competitionfrom grasses and forbs. Once established, therisk of wind and water erosion present withclean cultivation should be less than the simi-lar risk with annual crops, Drought-hardyshrubs and trees should make more effectiveuse of applied nutrients than water-stressed,herbaceous, annual crops.

If drought-adapted legumes are widely incor-porated into managed arid ecosystems, phos-phate and sulfate will ultimately become limit-ing and will have to be supplied. Both nutrientsstimulate legume production and can be sup-plied in single superphosphate.

Pesticide Requirements

It is difficult to imagine how the plant eco-systems described here would be any more orless susceptible to insect or bird attack than anyother ecosystem. Once established, perennialtree and shrub crops would survive competi-tion from grasses and forbs without weed con-trol measures. However, their productivityprobably will be greatly enhanced if herbicidesor cultivation were used to eliminate water

competition from grasses and forbs. For thefirst few years of shrub and tree stand estab-lishment, competition from grasses and forbsmust be eliminated either by herbicides orcultivation.

Machinery Requirements

A variety of options employing varyingdegrees of mechanization are available to estab-lish tree and shrub plantations. This author en-visions that most plantations will employ con-tainerized seedlings planted with a liter or twoof water. This can be accomplished manuallywith dibbles or post-hole diggers or mechani-cally with an 80 hp tractor pulling a trans-planter capable of planting 1,000 trees perhour, It may prove useful to establish a seedbedfor seedling transplant with the same level ofpreparation given to annual crops. However,after the first year an annual deep cultivationas required for annual crops will not be nec-essary. Where fruits are to be harvested (e.g.,jojoba, mesquite beans, etc.), light surface har-rowing or disking will prove useful for weedcontrol, to increase water infiltration, and toprovide a clean surface to pick up the fallenfruits. Pruning of tree and shrub crops will benecessary to allow access for harvesting offruits.

In biomass farming operations, where com-plete canopy closure is desired, annual cultiva-tion would be unnecessary and impossible tocarry out after canopy closure. An annualground preparation and planting, carefullytimed with arrival of rains to allow germina-tion and full use of the rainy season, will notbe necessary for the tree and shrub crops.Established annual and perennial crops willnot face a labor shortage at planting time asdo annual crops, The light cultivation that maybe useful with tree and shrub crops can be per-formed on a much less rigid schedule when la-bor, draft animals, and machinery are avail-able. If herbicides are available and acceptable,they can be used in lieu of light cultivation.Tree and shrub crops would require muchlighter equipment than annual crops and theannual site preparation necessary for annualscould be avoided.

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RESEARCH, DEVELOPMENT, AND IMPLEMENTATION OF ARID-ADAPTED PLANT ECOSYSTEM PRODUCTION TECHNOLOGIES

An outline of research required to developthese plants and cost estimates to do so aregiven in table 1. Research centers are proposedin six locations to collect and store germplasm,to plant germplasm nurseries, to reevaluatepromising nursery selections in larger sizedplots, to compare input/output resource ratioso f d i f f e ren t p l an t sys tems , to eva lua temonoculture and polyculture arid-adapted sys-tems, and to provide material and administr-ative support for the research.

The research program outlined in table 1 isappropriate for the first phase of the research,Extensive germplasm collections and plantingswould be required once at a cost of approx-imately $1,500,000. A funding effort 15 percentof the initial level would be appropriate afterinitial collections and plantings were made.Funds used for collections and plantings in thefirst phase should be allocated to weed and in-sect control, cultural operations such as har-vesting, pruning, and planting methods fornursery stock, and extension short courses dur-ing the second phase of the research.

Large genetically diverse germplasm collec-tions and promising plant selections are avail-able for some of the plants described here suchas jojoba, guayule, and atriplex species, Forother plants, germplasm collections and selec-tions of promising lines will have to be made.The plants that require germplasm collectionand selection and the methodology for accom-plishing that is outlined below.

Seeds should be taken and maintained assingle plant selections from Acacia tortilis andA. seya] in East Africa, from A. albida in Eastand West Africa, from Parkia biglobosa in WestAfrica, from Prosopis cineraria in the Mideastand India-Pakistan region, and from P. alba,P, chilensis, P. tamarugo, P. pallida, P. ar-ticulata, P. tamarugo, etc. in Argentina, Chile,Peru, Mexico, and Hawaii. Short, shrubby leg-umes of the genus Dalea should be collectedin Southwestern United States, Tephrosia i nTexan-Mexican area, and Zornia in Sahelian

Africa, Cactus genera such as Opuntia a n dCereus should be collected in SouthwesternUnited States. During these collections, at-tempts should be made to collect for as muchdiversity as possible as well as to collect foreconomically desirable characteristics, e.g.,heavy pod production, size and sweetness offruit, large trees, presence of large amounts ofleaf litter, and presence or absence of thorns.The plant should be collected over its entiregeographical and ecological range.

All of the collections should be evaluated inuniform plantations with a minimum of fourreplicates of five trees per replicate. For thetrees, height measurements should be performedthe first year, stem diameter measurements forbiomass estimation should be performed everyyear, and pod productivity measurementsshould continue indefinitely, One germplasmplanting should be evaluated in a 300 and 500to 600 mm annual rainfall regime in the India-Pakistan region, in East Africa, in West Africa,in the United States, and in South America.The purpose of the American planting wouldbe to provide American researchers with bio-logical research material and exposure to thesedifferent cropping systems. An additional siteshould be located near a seacoast to use sea-water irrigation to screen for salt-tolerantgermplasm.

The Hawaiian Niftal rhizobia collectionshould be evaluated for rhizobia for the leg-umes and techniques developed to ensure ef-fective modulation of field plantings, Soilsamples from native stands might containrhizobia with unique properties and should beused to inoculate native plants for comparativepurposes,

Most Acacias (Sief-el-Din, 1980) and probablyall Prosopis (47) are obligately outcrossed. Asa result, trees will not breed true and seed andclonal propagation techniques will be required,Both tissue culture propagation and traditionalrooting of cuttings should be examined,Rooting of stem cuttings is difficult for Pro-

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Table 1 .—Outline of Research Procedure

Level of supportper year($ 1,000)

100100100100200

100100

25

10010010010010010060

100

120

450(6 sites x 75)

1,200(200 x 6 sites)

180(30 x 6 sites)

1,200(200 x 6 sites)

400(200 x 2 sites)

600(200 X 3 sites)

1. Develop germplasm collections where none existA. Collect single tree selections of leguminous trees over broad range for:

1) pod production2) large size3) thorn characteristics4) leaf litter

B. Collect following genera:1) Acacia tortilis and A. seyal in East Africa2) Acacia albida in East and West Africa3) Parkia biglobosa in West Africa4) Prosopis cineraria in Indian-Pakistan region5) Prosopis alba, P. articulate, P. chilensis, P. nigra, and P. tamarugo

in Mexico, Hawaii, Southwestern United States, Argentina, Chile,and Peru

6) Make cactus collections in Southwestern United States and Mexico7) Short, shrubby legumes, Dalea in Southwestern United States,

Tephrosia in deep South, and Zorrria in Sahelian Africa2. Obtain good selection of following arid crops already subjected to

germplasm collection and screening:A. Jojoba—Drs. Yermanos and HoganB. Guayule—USDAC. Euphorbia—Dr. CalvinD. Atriplex— Drs. McKell and GoodinE. Leucaena—Dr. Brewbaker

3. Plant out four replicates of five trees (plants) of all accessions forgermplasm nursery at a 300 mm and 500-600mm annual rainfallregime in:A. East Africa, e.g., SudanB. West Africa—SenegalC. India-Pakistan regionD. South AmericaE. Southwestern United StatesF. Site along coast to irrigate with seawater for salinity trials

4. Evaluate Niftal collection of rhizobia suitable for tree legumes.Develop techniques to insure effective modulation.

5. Conduct protein, sugar, fiber, and toxicity analyses on pods that areproduced.

6. Develop clonal propagation techniques at central facility:A. Rooting of cuttingsB. Via tissue culture

7. Evaluate germplasm nursery for:A. Height measurements first yearB. Stem diameter measurements yearlyC. Pod production and/or pod chemical charactersD. Make clones of outstanding single trees

8. Evaluate clonal outstanding material in replicated 0.1 ha minimum-sized plots.

9. Multiply and distribute best selections to interested individualsand organizations.

10. Evaluate comparative advantages of selections developed above inmono- and poly-culture with Opuntia, jojoba, guayule, atriplex, etc.

11. Evaluate large N fixing trees with staple cereal crops infield plantings.

12. Evaluate short N fixers with jojoba, guayule, saltbush, etc.

5,735 ‘ Total direct research4,265 Support facilities, travel, secretarial, library, statistical analyses, computer

services, etc.Grand total

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sopis. To achieve success for large-scale plan-tings, a thorough evaluation of rooting meth-ods including evaluation of mist, atomizedfogging, and tent humidification devices,screening trials of hormone mixtures, evalua-tion of out-of-doors and greenhouse grownstock, and use of growth chambers to deter-mine optimal light, temperature and humiditylevel for cuttings will be required.

Most annual legumes are highly self-fertileand breed true to type. These selections willnot require vegetative propagation, but germ-plasm multiplication areas will be required.Laboratory analysis of crude protein, sugar,and fiber should be conducted on pods, fruito r o the r economica l ly impor tan t p l an tstructure.

Single tree selections should be made fromthe germplasm nursery on the basis of: 1 )height and biomass determinations, 2) pod pro-duction and pod chemical characters, 3) pres-ence or absence of thorns, and 4) other char-acteristics deemed important. These selectionsshould be clonally multiplied and reevaluatedwith four replicates of 0.1 ha minimum sizedplots per selection. Sufficient quantities of theclonally multiplied material should be made toallow distribution to requesting individuals andorganizations.

Once reasonably productive selections of theleguminous trees and cactus have been devel-oped, they should be compared with advancedstrains of jojoba available from Yermanos andHogan, from guayule available from USDA,and from saltbush available from McKell andothers. The comparative advantages and rela-tive resource requirements for these cropsshould then be evaluated as monoculture andpolycultures. The large nitrogen fixing trees P.cineraria and A. albida should be evaluated invarious spatial configurations with the staplecrops millet, sorghum, and peanuts. The shortshrubby and herbaceous legumes of the generaTephrosia, Zornia, and Dalea should be eval-uated with jojoba, guayule, saltbush, andopuntia.

As with all crops, solutions to weed prob-lems, insect problems, and cultural practices

will have to be developed for these ecosystems.Herbicide and cultivation methods should beexamined for weed control and insecticide,biocontrol, and integrated pest managementshould be evaluated for insect control. Har-vesting, pruning, plant spacing, and plantingmethods also require development.

It has been the experience of Dr. Yermanoswith jojoba and of this author with mesquitethat once genetically superior strains have beenproduced the demand for the strains and thetechnology associated with them will greatlyoutstrip the supply. Elderly ladies with 100square feet of desert in their backyard in YuccaValley, California, business executives, andministers of agriculture in arid developingcountries will ask the project leader to visittheir backyard or country to set up the appro-priate technology. It is imperative to developsufficient plant material for further multiplica-tion and to train extension personnel to helpfarmers, businessmen, or government leadersuse the technology. Short extension coursesprovided by staff involved in germplasm nur-series and evaluation centers would be an idealmethod of disseminating the information.

The staff of the germplasm nursery and eval-uation centers would require a Ph.D. projectleader for: 1) Acacia tortilis and A. seyal, 2)Acacia albida, 3) Prosopis cineraria, 4) Parkiabioglobosa, 5) the American Prosopis species,6) the shrubby and herbaceous legumes, 7) thecactus, 8) the atriplex complex, 9) guayule, 10)jojoba, and 11) other overlooked species. A cen-tral tissue culture and clonal propagation cen-ter should develop the techniques for clonalpropagation and have at least two Ph.D.’s, sixB.S. ’S and/or master’s level technicians and sixto eight support personnel preparing media,washing dishes, etc. Each research centershould have two B.S. or M.S. full-time person-nel and six nonskilled laborers rooting cuttingsand/or multiplying germplasm for researchand/or further distribution. The availability ofa statistician and computer for analysis of fieldexperiments is essential.

A major effort will be required to developsupport facilities for research in arid develop-

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ing countries of Africa. Telephone service, mail solutely essential that the plant research be con-service, ground transportation, and freight ducted in the climate and on the soils whereservices to and from Europe are too unreliable it is to be used and this requires developmentto make effective research possible in East of support services for the research.Africa and perhaps other countries. It is ab-

CONSTRAINTS FACING DEVELOPMENT AND IMPLEMENTATIONOF ARID-ADAPTED PLANT PRODUCTION TECHNOLOGIES

There are no major or theoretical scientificconstraints on using these technologies, but ap-plied research efforts are required in severalareas. Techniques need to be developed forclonal propagation of the species describedhere—both rooting of cuttings and tissue cul-ture. Planting techniques, greenhouse and fieldcultural practices need to be optimized. A con-tinued effort to identify and propagate bettergenetic selections is required,

Environmental constraints to developmentof these systems are minimal, as increasedvegetation in arid developing countries has theeffect of halting desertification. There are, how-ever, serious cultural constraints to develop-ment of perennial production systems, Forinstance, in Sahelian Africa the perennial vege-tation is viewed as community-owned (48),Thus, the pods or fruits from trees can be takenby anyone, even if the trees are on privatelyowned land,

Similarly, people can cut branches from non-protected species of trees for fuelwood evenif the landowner planted the trees for his ownfuelwood use. Freely roaming goats that eatyoung seedlings constitute a major problem inestablishing perennial production systems.Control of the movement of goats is probablyan insoluble cultural problem and thus goat-proof devices to protect young seedlings willhave to be devised,

Political constraints on the development ofthese technologies stem from politicians’ andbureaucrats’ unfamiliarity with use of theseperennial crops, This is most accurately de-scribed in Pelissier’s explanation of whv

Acacia albida is not more widely used in WestAfrica (14).

One cannot help but be astonished that anagronomic research center established to studythe Serer people (in Senegal, West Africa) is notmore interested in the methods and effective-ness of native farming systems. These re-searchers ignore the milieu of naturally-regen-erating Acacia stands by which they aresurrounded. This mark of indifference and in-comprehension for African techniques is toooften manifest by European specialists or thosetrained in Europe. In order to promote theirown cultural values, these researchers use theterms “modern” and “scientific” as if labora-tory and field techniques are completely inap-plicable, for social or economic reasons, to thetruly native farming systems.

Acacia albida suffers from the division of thetechnical services. The agronomist regards thepresence of the tree in the field as an adver-sary to be eliminated. The forester is not inter-ested in the tree because Acacia albida does notgrow in what could be termed a forest and is,therefore, not capable of being dealt with bystandard silviculture concepts. The role ofAcacia albida, including its growth and ger-mination conditions, illustrates its marvelouscharacter which cannot be dissociated from itsgenuine agricultural setting and illustrates thenecessity for deep-seated action to aid thefarming population. At this time in our in-timate knowledge of political techniques for ru-ral management, an end must be placed to theabsurd division of agriculturally relateddisciplines which enclosures agricultural de-velopment specialists. It is not lack of concernin the development specialists that causes thisproblem but rather their overspecialized train-ing, and above all the administrative structuresthat thwart their action and hinder an in-tegrated development plan which alone can beeffective,/

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EFFECT OF TECHNOLOGY IMPLEMENTATION ON CAPITAL, LABOR,AND LAND REQUIREMENTS

The initial inputs required for the systems de-scribed in this paper are low but the output/in-put ratio of the system is high. Yield increaseswill tend to stimulate more investment in thetechnology. For example, assume a farmer willplant 1 ha with 200 Prosopis trees, The whole-sale seedling cost should be approximately$0.15, requiring an outlay of $30. These seed-lings could be planted on his own land withonly a shovel, and some buckets for wateringthe seedlings after transplant. If planted in re-gions at 500 mm annual rainfall, at year 10 thetree should be producing 4,000 kg of pods perhectare (16). These pods typically have proteinand nitrogen contents of 12.5 percent and 2.0percent, respectively (4). Thus, the pods con-tain 80 kg of N, which is worth $40 at today’sprice of $50 per 100 kg of N. To achieve cap-ture of 80 kg of N in pods from chemical fer-tilization, at least double the amount of nitro-gen in the pods, or 160 kg of N, would havehad to have been applied. Thus, the cost to pro-vide the nitrogen found in the pods would havebeen $80 per year. Recalling that the farmer’scash outlay for seedlings was $30, his annualreturn on the seedling investment from nitro-gen alone is 270 percent. His $30 investmentin seedlings probably would be returned from60 kg of N fixed by the plants in 2 to 3 years.

Because most of these trees are outcrossedand planted only once every 30 to 50 years, itwould be most advantageous to plant clonalmaterial from outstanding individual trees.Thus, commercial tree nurseries would be re-quired to supply young trees to villages in thecountryside. Hopefully, farmers would recog-nize the importance of obtaining high quality,clonally propagated seedlings for long-termplantings, and would support commercialvillage level nurseries that would deliver su-perior genetic stock to the local population,

Fertilizers other than nitrogen would be re-quired. Phosphate and, to a lesser extent,sulfate fertilizers stimulate nitrogen fixation inlegumes and would be a worthwhile invest-ment. Phosphate fertilizers have approximatelythe same unit price as nitrogen fertilizers butonly 10 percent as much phosphate is required.Annual crops such as maize may capture only40 to 50 percent of applied fertilizer partiallybecause of leaching beyond the root zone (37).Shrubs and trees such as Acacia, Prosopis, andjojoba commonly root to 10 meters (13) andwould achieve higher capture ratios of appliedfertilizer.

There is no reason to suspect that any moreor less pesticides would be required than inother kinds of systems since insects would bejust as likely to attack tree or shrub crops asannual crops. Due to the low till or no tillagerequirement for many of these shrub and tree-based production systems, agricultural machin-ery requirements would be expected to be lessthan those of conventional plant productionsystems. Most harvesting in arid developingcountries is done by hand. With increasedyields of traditional crops stimulated by asso-ciation with leguminous companion crops, thedemand for labor at harvesting time will in-crease. Production of large quantities of treelegume pods, jojoba nuts, and fuelwood willalso increase the labor demand for harvestingoperations,

The low requirements for tillage machineryand the lack of a nitrogen fertilizer requirementwill greatly reduce credit requirements forthese two traditionally high credit requiringareas, On the other hand, the several years’wait prior to harvest of perennial crops will re-quire credit to pay for the seedling costs.

100

IMPACT OF WIDE-SCALE TECHNOLOGY IMPLEMENTATIONON THE SOCIOECONOMIC STRUCTURE OF AGRICULTURE IN

DEVELOPING

Most of the plant systems (technologies) dis-cussed in this report are widely used by sub-sistence farmers in the developing countries.The plants used are primarily volunteer seed-lings of unselected genetic stock that the farm-ers may prune and care for (40). This systemis comparable to use of unselected races ofmaize and wheat as would have been done inthe late 1800s in the United States and Europe.Placing these widely used, but scientifically un-manipulated plants into a research and devel-opment framework will probably yield increasessimilar to that achieved by first inbred and thenhybrid lines of maize and other cereals.

Vigorous, naturally occurring tree legumehybrids have been observed and clonally pro-pagated by this author and demonstrate theease with which hybrids can be formed. Maizeyields increased from less than 20 bushels peracre in the early 1900s to close to 100 bushelsper acre at present. The plant systems de-scribed here probably have the potential ofachieving the same yield increases. Perhaps atwo- to three-fold increase in plant productivitycan be expected in 5 to 15 years and a five- toten-fold increase in 50 to 100 years. Unlikemaize, these systems are based around nitro-gen-fixers and will not require fossil-fuel-

COUNTRlES

derived and energy-intensive nitrogen fer-tilizers.

Assuming these kinds of yield increases intree legume pod production, fuelwood produc-tion, cash crop production, soil fertility, andensuing staple food production, returns tofarmers can be expected to increase in thesame approximate fashion. As the farmers in-come rises, his demands for goods and serv-ices will rise and stimulate the economy as awhole. A greater tax base will then be avail-able to support more roads, schools, and healthservices, which will in turn decrease unem-ployment.

The economy of a country with an agrariansociety is inextricably tied to the primary pro-ductivity of the ecosystem. As long as substan-tial progress is being made toward achievingthe economic goals of the rural population,there will be fewer economic grounds foster-ing political instability. Past efforts to stabilizethe political systems of arid developing coun-tries, such as Iran, with military hardware sys-tems have proven futile. It is imperative to de-velop plant systems that have the capability todirectly impact the smallest farmers on thelocal level to increase his well-being and de-crease economically fostered political unrest.

101

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References

Ahmed, G., “Evaluation of Dry Zone Afforesta-tion Plots, ” Pak. J. Forestry 168-175, 1961.Aschmann, H., Professor of Earth Sciences,University of California-Riverside, personalcommunication, 1979.Basak, M. K,, and Goyal, S. K,, “Studies on TreeLegumes. 111. Characterization of the Symbiontsand Direct and Reciprocal Cross-InoculationStudies With Tree Legumes and Cultivate Leg-umes, ” Plant and Soil 56:39-52, 1980.Becker, R., and Grosjean, O. K. K., “A Composi-tional Study of Pods of Two Varieties of Mes-quite (Prosopis glandulosa, P. velutina), ” J.Agric. Food Chem. 28:22-25, 1980.Brewbaker, J. L., and Hutton, E. M., “Leucaena,Versatile Tropical Tree Legume, ” In: New Agri-cultural Crops, G. A. Ritchie (cd.). Amer. Assoc.Adv, Sci. Symp. vol. 38 (Boulder, CO.: WestviewPress, 1979).Burgress, R, L, (cd.), “Economic Developmentof Desert Plants, ” Sponsored by American In-stitute of Biological, 1980.Calvin, M., “Petroleum Plantations for Fuel andMaterials, ” Bioscience 29, 533-538, 1979.Charreau, C., and Vidal, P., “Influence deI’Acacia albida (del) Sur le Sol, NutritionMinerale, et Rendements des Mils Pennisetumau Senegal, ” Agron. Trop. 20:600-626, 1965.Dancette, C., and Poulain, J. F., “Influence ofAcacia albida on Pedoclimatic Factors andCrops Yields,” African Soi]s 14:143-184, 1969.D’Antoni, H. L., and Solbrig, O. T., “Algarrobosin South American Cultures: Past and Present, ”Mesquite, Its Biology in Two Desert Ecosys-tems, B. B. Simpson (cd.) (Stroudsburg, Phila.:Dowden Hutchinson & Ross, 1977).Felger, R. S., “Ancient Crops for the Twenty-first Century, ” New Agricultural Crops, G. A.Ritchie (cd,), Amer. Assoc. Adv. Sci. Symp. vol.38, (Boulder, CO: Westview Press, 1979), pp.5-20.Felker, P., “State of the Art: Acacia albida asa Complimentary Permanent Intercrop WithAnnual Crops,” USAID Information Services,Washington, DC, 1978.Felker, P., “Mesquite: An All-Purpose Legumi-nous Arid Land Tree, ” New Agricultural Crops,G. A. Ritchie (cd.), Amer. Assoc. Adv. Sci.Symp., vol. 38 (Boulder, CO: Westview Press,1979).Felker, P., and Bandurski, R. S., Uses and Po-tential Uses of Leguminous Trees for MinimalEnergy Input Agriculture, 33:172-184, 1979,

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Felker, P., and Clark, P. R., “Nitrogen Fixation(acetylene reduction) and Cross-inoculation in12 Prosopis (mesquite) Species, ” Plant and Soil(in press), 1980.Felker, P., Clark, P. R., Osborn, J., and Cannell,G. H., “Nitrogen Cycling-water Use EfficiencyInteractions in Semi-arid Ecosystems in ReIa-tion to Management of Tree Legumes (Pro-sopis), ” H. N. LeHouerou (cd.). Browse inAfrica Symposia, Addis Abba, Ethiopia, 1980.Fischer, R. A., and Turner, N. C., “Plant Pro-ductivity in the Arid and Semi-arid Zones, ”Ann. Rev. P]. Physiol, 39:277-317, 1978.Glicksman, M., and Sands, R. E., “Gum Ara-bic,” Industrial Gums, Znd Edition, R. L.Whistler and J. N. BeMiller (eds,) (AcademicPress Publishers, 1973), pp. 197-263,Goodin, J. R., “Atriplex as a Forage Crop forArid Lands,” New Agricultural Crops, G. A. Rit-chie (cd.), Amer. Assoc. Adv. Sci. Symp., vol.38 (Boulder, CO: Westview Press, 1979).Gupta, R. K., and Balera, G. S., “ComparativeStudies on the Germination, Growth, and Seed-ling Biomass of Two Promising Exotics in theRajasthan Desert, Indian Forester 280-285,1972.Habish, H. A., and Khairi, S. M., “Modulationof Legumes in the Sudan. II. Rhizobial Strainsand Cross-inoculations of Acacia spp,, ” Exp.Agric. 6:171-176, 1970,Hadri, H., “Ingenieur Principal a 1’INRF,”INRF-B.P. 2 Ariana, Tunisia. personal commu-nication, 1980.Hogan, L., “Jojoba: A New Crop for Arid Re-gions, ” New Agricultural Crops, G. A. Ritchie(cd.), Ameri. Assoc. Adv. Sci. Symp., vol. 38(Boulder, CO: Westview Press, 1979).Houri, A. E., “Forestry Research Institute, ”Khartoum, Sudan, personal communication,1979,Kaul, R. N,, “Afforestation in Arid Zones,” Dr.W. Junk, N. V. Publishers, The Hague, 1970.Khalifa, K, O., Sudan Council of Churches,Khartoum, Sudan, personal communication,1979.LeHouerou, H. N. (cd.), “Browse in Africa Sym-posia, ” International Livestock Center forAfrica (ILCA), Addis Ababa, Ethiopia, 1980.Lopez, J. J., Gasto, J. M., Nava, R., and Medina,J. G., “Ecosistema Opuntia streptacantha, LeMaire, Universidad Autonoma Agraria AntonioNarro, Saltillo, Coahuila, Mexico, 1977.Lorence, F. G., “Importancia Economia de 10SMezquites (Prosopis spp.) an Algunas Estadosde la Republica Mexicana, ” Mezquites y

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Huizaches, Ediciones de] Instituto Mexicano deRecursos Naturales Renovable, A. C., MexicoD. F,, 1970.Lorence, F. G., National School of Agriculture,Chapingo, Mexico, personal communication,1980.Mann, H, S., and Shankarnarayan, K. A., “TheRole of Prosopis cineraria in an AgropastoralSystem in Western Rajasthan, ” Browse inAfrica Symposia, H. N, LeHouerou (cd,), AddisAbaba, Ethiopia, 1980.McKell, C, M,, “Shrubs-A Neglected Resourceof Arid Lands, ” Science 187:803-809, 1975.Monjauze, A., and LeHouerou, H. N., “Le Roledes Opuntia clans l’Economic Agricole NerdAfricaine, ” Bull. de l’Ecole Nationale Supe-rieure d’Agriculture de Tunis, 8-9, 85-164, 1965.National Academy of Sciences, “Tropical Leg-umes” (Washington, DC: Resources for the Fu-ture, 1979).National Academy of Sciences, “Jojoba Feasi-bility for Cultivation on Indian Reservations inthe Sonoran Desert Region, ” Washington, DC,1977.National Academy of Sciences, “Leucaena:Promising Forage and Tree Crop for the Trop-ics,” Washington, DC, 1977.Olsen, R. J., Hensler, R. F., Attoe, O. J., Witzel,S. A., and Peterson, L. A., “Fertilizer Nitrogenand Crop Rotation in Relation to Movement ofNitrate Nitrogen through Soil Profile,” Soil Sci.Soc, Amer. Proc. 34:448-452, 1970.Parker, K. W,, and Martin, S. G., “The MesquiteProblem on the Southern Arizona Range,”U. S.D.A. Circ. 968, 1952.Peck, R,, Report to International DevelopmentResearch Center, Ottawa, pp. 43-44, undated.Pelissier, P., “Les Paysans du Senegal—LesCivilisations Agraires du Cayor a la Casa-mance, ” Imp. Fabregues, Saint Yrieux (HautVienne), pp. 265-274, 1967.Pellew, R., “The Production and Consumptionof Acacia Browse for Protein Production, ”Browse in Africa, H. N. LeHouerou (cd.), AddisAbaba, Ethiopia, 1980.Ritchie, G. A. (cd,), New Agricultural Crops,Amer. Assoc. Adv. Sci. Symp., vol. 38 (Boulder,CO: Westview Press, 1979).Rol, F., “Locust Bean Gum,” Industrial Gums,2d cd,, R, L, Whistler and J. N, BeMiller (cd.).

(New York: Academic Press Publishers, 1973),pp. 323-335.

44. Salinas, H. E., and Sanchez, S. C,, “Estudio delTamarugo Como Productor de Alimento delGanado Lanar en la Pampa del Tamarugal, ” ln-forme Technico No. 38, Instituto Forestal, Sec-cion Silvicultura, Santiago, Chile, 1971.

45. Seif-el-Din, A. G., Gum Research Officer, Agri-cultural Research Corporation, Gun ResearchDivision, El Obeid, Sudan, personal communi-cation, 1979.

46. Shankar, V., Dadhich, N. K., and Saxena, S, K.,“Effect of Khejri Tree (Prosopis cineraria, Mac-bride) on the Productivity of Range GrassesGrowing in Its Vicinity, ” Forage Res. 2:91-96,1976,

47. Simpson, B. B., “Breeding Systems of DominantPerennial Plants of Two Disjunct Warm Eco-systems, ” Oeco/ogia (Berl.) 27:203-226, 1977.

48. Thomson, J, T., “How Much Wood Would a

49

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Peasant Plant,” Public choice analysis of institu-tional constraints on firewood production strat-egies in the West African Sahel. Manuscriptsubmitted to Johns Hopkins University Press,1980.Tiedemann, A. R., and Klemmedson, J. O., “Nu-trient Availability in Desert Grasslands SoilsUnder Mesquite (Prosopis juliflora) Trees andAdjacent Open Areas,” Soil Sci. Soc. Amer.Proc. 37:107-111, 19730

Vietmeyer, N., “Guayule: Domestic NaturalRubber Rediscovered, ” New AgriculturalCrops, G, A. Ritchie (cd.), Ameri. Assoc. Adv.Sci. Symp., vol. 38 (Boulder, CO: WestviewPress, 1979), pp. 167-176.

51. Wight, J. R., and Black, A. L., “Range Fertiliza-

52

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tion: Plant Response and Water Use,”]. RangerManage. 32:345-349, 1979.Xolocotzi, E. H., “Mexican Experience, ” AridLands in Transition, H, E. Dregne (cd.), Amer.Assoc. Adv. Sci., Publication No. 90.317-344,1970.Yermanos, D. M., Professor of Plant Sciences,University of California-Riverside, personalcommunication, 1980.

54. Zelada, L, G., Coordinator, Programma Pampadel Tamarugal, CORFO, Santiago, Chile, per-sonal communication, 1980.

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Work Statement

Topic

Development of low energy input technol-ogies to increase and stabilize productivity ofagricultural ecosystems in dry regions of lessdeveloped countries. The contractor shall:

1.

2.

3.

4.

Describe how the technologies operate andwhat beneficial or adverse impacts theyhave or might have on enhancing the sus-tained production of food and forage fromtropical and subtropical soils.Describe where the technologies are beingused. Describe whether each technologyis being used on a commercial level, a sub-sistence level, as a pilot program, or isbeing applied only in the research state.Describe who is conducting the major re-search on the technology. Describe whatorganizations (AID, FAO, and others usingU.S. funds) are funding development of thetechnology and what organizations are im-plementing it on a project scale.Explain in some technical detail how thesetechnologies increase or decrease the needfor fertilizers, pesticides, irrigation, andmachinery when applied to tropical/sub-tropical soils.Discuss the potential role of these technol-ogies being used to restore, improve, orsustain in perpetuity the food and forageproductivity of tropical and subtropicalsoils, and the likelihood that they will beused widely.

We appreciate that the author may not be aspecialist in economics or sociology; however,his experience and insights on the followingquestions are still of interest to OTA, especiallyas they relate to lesser developed countries.Therefore the contractor shall:

5. Describe a plausible research, develop-ment, and implementation scenario inwhich these technologies realize their po-tential in enhancing productivity of trop-ical soils. What organizations would be in-volved? What levels of capital and trained

6.

7.

8.

personnel would be necessary? What de-gree of attitudinal changes would be nec-essary for consumers, farmers, govern-ment agricultural experts, bureaucrats,politicians, foreign advisors, policy makersin foreign aid or lending institutions, etc. ?What biophysical (soils, climate, topogra-phy), cultural, and socioeconomic condi-tions would be most conducive to suc-cessful implementation of the technology?Where do these conditions exist or whereare they likely to develop? To indicate thepriority of the various steps that need tobe taken on this technology, contractorshall discuss how he (if he were the headof a wealthy foundation) would spend $10million on research, development, or im-plementation of the technology.Describe the major scientific, environ-mental, cultural, economic, and politicalconstraints on development and imple-mentation of these technologies.Describe how implementation of thesetechnologies would affect the need, in theregion where they were implemented, forinputs of capital (agricultural chemicals,machinery, credit, seed, and other mate-rials from the implemention farm), labor,and land.Describe what the impact of wide-scale im-plementation of these technologies wouldbe on the socioeconomic structure of agri-culture in the implementing regions. Forexample, does the technological imple-mentation give rise to economies of scale,or diseconomies of scale, that would makelarge or small farm units more competi-tive? How would the technologies eitherdisplace or create demand for farm laborers.

Deliveries

The contractor shall deliver to OTA theoriginal copy (not a reproduction) of the type-written 25- to 35-page report, acceptable toOTA, with abstract and literature citations, byNovember 24, 1980.

Chapter VII

Azolla, A Low Cost AquaticGreen Manure forAgricultural Crops

A. LumpkinSoil ScienceAgriculture

ThomasDepartment of Agronomy and

College of TropicalUniversity of Hawaii

Honolulu, Hawaiia n d

Donald L. PlueknettConsultative Group on international

Agricultural ResearchWorld Bank

Washington, D.C.

Contents

Page

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107What Is Azolla? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107What Are the Benefits of Using Azolla? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

The Present Status of Azolla . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111Where Azolla Is Being Used in Agriculture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111How Azolla Is Used as a Green Manure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112Who Is Doing Azolla Research? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114What Organizations Are Financing Azolla Research? . . . . . . . . . . . . . . . . . . . . . . 114

Azolla’s Effect on the Need for Agricultural Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . 115Fertilizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115Pesticides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. ... ... ...O... 115Irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115Machinery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

The Potential Use of Azolla . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116How Does Azolla Affect the Productivity of Tropical Soils? . . . . . . . . . . . . . . . . 116The Potential Use of Azolla . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

A Research, Development, and Implementation Program . . . . . . . . . . . . . . . . . . . . . . 117The Program Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117What Organizations Should Be Involved? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118What Is the Necessary Level of Financial Support?. . . . . . . . . . . . . . . . . . . . . . . . 118What Are the Personnel Requirements? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119What Are the Attitudes of Those Who Would Be Affected? . . . . . . . . . . . . . . . . . 119What Are Conducive Conditions for Implementation of the Technology? . . . . . 119Where Do Conducive Conditions Exist and Where Are

They Likely to Develop? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120What Is the Sequence of Steps Leading to Successful Implementation?. . . . . . . 120

Constraints on the Development and Implementation of Azolla Technology . . . . . . 120Scientific Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120Environmental Constraints. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120Cultural and Economic Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121Political Constraints .. .. .. .. .<. ... .$..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

The Effect of the Implementation of Azolla Technology on the Need for Inputs . . 122Capital . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122Farm Labor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122Land. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

Figures

Figure No. Page

l. Azolla . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1082. Azolla as Food and Fodder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1103. Geographic Distribution of Azolla . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1114. Incorporating Azolla Into Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

Chapter Vll

Azolla, A Low Cost Aquatic GreenManure for Agricultural Crops

INTRODUCTION

The air we breathe is 79 percent nitrogen.Plants need nitrogen to make the proteins thatallow them to harvest sunlight and carry on

natural processes. Unfortunately, nitrogen inthe air is in an inert N2 form that cannot beused by plants. Only two kinds of organismshave the ability to convert inert atmosphericnitrogen to a usable form such as ammonia,These two organisms are blue-green alga (cy-anobacteria) and certain species of bacteria.Rhizobium bacteria are the nitrogen-fixingpartners of the well-known legume/Rhizobiumsymbiosis of soybeans, alfalfa, etc. The blue-green alga anabaena are the nitrogen-fixingpartners of the virtually unknown Azolla/Ana-baena symbiosis,

Until this century, nitrogen-fixing bacteriaand blue-green alga, existing under freelivingor symbiotic conditions, produced most of thenew nitrogen entering the cropping system.Almost all farmers had to include legumes intheir crop rotation in order to maintain soilfertility. This traditional practice continueduntil the discovery of fossil-fuel-dependentmethods of producing nitrogen fertilizer thatradically changed the economics of agriculture,The use of legumes in crop rotation was soonconsidered to be too expensive and trouble-some and fell into disuse, except when grownas a cash crop. The change was most appar-ent in developed countries and in developingcountries that adopted the “green-revolution”technology.

However, during the 1970s this change beganto reverse itself, The rapidly rising price offossil fuel-dependent nitrogen fertilizers causedthe economics of agriculture to shift again,Rising prices are causing researchers to seekalternative methods for producing synthetic

fertilizer and causing farmers to reconsidertraditional methods for maintaining soil fer-tility.

The traditional legume crops are and willcontinue to be the most commonly used ni-trogen-fixing green manures, especially forupland crops. However, they have certainweaknesses for rice farmers. One of theseweaknesses is that rice is traditionally grownon the most fertile and, consequently, inten-sively managed land. Rice farmers are reluc-tant to use part of the valuable growing seasonon a relatively slow-growing, legume greenmanure crop, Another problem is that manyrice paddies are flooded or waterlogged, par-ticularly during the potentially productive earlypart of the rice season when most of the trans-planted rice is still in the nursery beds. Unfor-tunately, under waterlogged or flooded condi-tions most legumes cannot grow or fix nitrogen,so usually the paddy fields stand idle for amonth or more while the rice seedlings maturein the nursery beds. The fast-growing aquaticAzolla has neither of these two weaknesses,

What Is Azolla?

Azolla is a genus of small aquatic ferns thatare native to Asia, Africa, and the Americas(figure 1), Three Azolla species are native toparts of the United States, They live naturallyin lakes, swamps, streams, and other bodies ofwater, Some have been spread by man or nat-ural means to various parts of the world. Someare strictly tropical or subtropical in nature,while others grow and thrive in either temper-ate or tropical climates. Azolla has been of in-terest to botanists and agriculturists for yearsbecause of its symbiotic relationship with anitrogen-fixing, blue-green alga, Anabaena.

107

108—

Figure 1.—Azolla

Vietnam.

The Azolla/Anabaena Relationship

The most remarkable feature of azollasymbiotic relationship with the blue-green

is itsalga,

Cells of the nitrogen-fixing blue-green algae, Anabaena, looklike a string of beads. The larger egg-shaped cells special-ize in producing nitrogren fertilizer while the more numer-ous smaller cells harvest sunlight.

Anabaena azollae. The delicate fern providesnutrients and a protective leaf cavity for theAnabaena, which in turn provides nitrogen forthe fern. Under suitable field conditions, thefern/alga combination can double in weightevery 3 to 5 days and fix atmospheric nitrogenat a rate exceeding that of the legume/Rhizo-bium symbiotic relationship. Azolla can ac-cumulate up to 2 to 4 kilograms of nitrogen/

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ha/day (equivalent to 10 to 20 kg of ammoniumsulfate), and since the Azolla/Anabaena com-bination grows in aquatic conditions, it canprovide a potential nitrogen source for floodedcrops such as rice. The exploitation of this po-tential is a challenge to agricultural scientists.

What Are the Benefits ofUsing Azolla?

Producing Nitrogen Fertilizer forincreasing Crop Yields

Azolla plants are described by the Chineseand Vietnamese as being miniature nitrogenfertilizer factories. Indeed the Vietnamese callthem indestructible fertilizer factories, sinceazolla continued to produce nitrogen fertilizerfor Vietnamese rice paddies even during theheight of the Vietnam war.

The nitrogen fertilizer fixed by azolla be-comes available to the rice after the azolla matis incorporated into the soil and its nitrogenbegins to be released through decomposition.In 25 to 35 days azolla can easily fix enoughnitrogen for a 4 to 6 ton/ha rice crop duringthe rainy season, or a 5 to 8 ton/ha crop underirrigation during the dry season.

Maintaining Soil Fertility

As a green manure, azolla’s influence on soilfertility is due to its organic matter and nitro-gen. A humus compound is formed as a resultof the incorporation and decomposition ofazolla. Humus increases the water holding ca-pacity of soil and promotes aeration, drainage,and the aggregation essential for highly pro-ductive soils, Organic matter can bind togethersoil particles and makes clayey soils morefriable.

In addition to its influence on soil physicalproperties, azolla is important in the cyclingof nutrients, While azolla is growing in thepaddy, it fixes nitrogen and also absorbs nu-trients out of the water that might otherwisebe washed away. When the azolla is incor-porated into the soil and humus is formed,these nutrients are slowly released into the soilas decomposition progresses.

Even though azolla appears to be a ratherdelicate plant that would rapidly decompose,it actually takes six weeks or more for most ofthe nutrients to be released because the planthas a rather high lignin content. Slow decom-position gives a natural slow release effect thatis ideal for efficient absorption of the nutrientsreleased. Another factor in azolla effectivenessas a green manure is its low carbon to nitro-gen ratio of about 10:1. This high ratio ensuresthat azolla nitrogen will not be tied up bybacteria that are involved in decomposition ofan over abundance of carbonaceous plantresidues.

Producing Fodder for Pigs, Ducks,and Fish

Azolla has traditionally been used as a fod-der throughout Asia and parts of Africa. It isfed to pigs, ducks, and fish (figure 2), The grasscarp (Ctenopharyngodon idella), Israeli Carp(Cyrinus carpis), and Tilapia mossambica pre-fer azolla over most other aquatic weeds as asource of food, Small lots of azolla growing incanals and ponds as food for pigs and ducksare ubiquitous throughout southern China.Azolla as a fodder probably has a longer his-tory than as a green manure, There may evenbe potential for direct consumption by man,In India, women make a tasty deep fried dishof azolla mixed with batter (7),

On a dry weight basis, azolla has a proteincontent between 13 to 24 percent, One hectareof azolla can produce 1 to 2 tons of fodder perhectare per day, equivalent to 10 to 30 kg ofprotein per day. When these statistics are con-sidered, azolla has a tremendous potential asa fodder crop in developing countries and alsoin the United States.

Recent work in India at G. B. Pant Univer-sity indicates that azolla maybe useful as a fod-der for cattle. In trials there, growing heifersgained 0.33 kg/day when fed 0.9 kg of driedazolla with 2.1 kg of a 2:1 ratio of dry wheatstraw and sugarcane tops. Control animals thatwere fed the same amount of wheat straw andsugarcane tops, but also received 1.5 kg of aconcentrate feed, gained only 0.14 kg/day (l).

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Figure 2.— Azolla as Food and Fodder

Although azolla is most commonly used(center) and fish and as a compost (right)

as an organic fertilizer for rice, it can also be used as a fodder for pigs (left), duckfor upland crops. Many of the pigs which are grown to produce China’s famous Jin-

hua hams are fed on a diet which includes azolla.

Azolla is a preferred forage for many species of herbivorous fish. Azolla may also have potential for direct consumptionman if attractive uses can be developed. The photo on the right shows a deep fried dish of azolla mixed with batter.

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Suppressing the Growthof Aquatic Weeds

Agricultural economists have estimated thatAsian farmers, particularly women, spendmore time weeding than on any other activityrequired for rice production. Although re-search is insufficient, it is commonly believedthat azolla suppresses the growth of certainaquatic weeds. Weed growth is suppressedwhen azolla forms a thick, virtually light-proofmat. There are probably two mechanisms for

this suppression, the most effective being thelight-starvation of young weed seedlings by theblockage of sunlight. The other is the physicalresistance to weed seedling emergence createdby a heavy, interlocking azolla mat. In someweed-infested rice fields, the benefit fromazolla weed suppression may even surpass itsbenefit as a nitrogen source. Rice seedlings arenot affected by azolla’s weed suppression ef-fect because, when transplanted, they standabove the azolla mat.

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THE PRESENT STATUS OF AZOLLA

Where Azolla Is Being Used inAgriculture

Azolla is already being grown commerciallyin China and Vietnam, where its usefulness hasbeen known for years, Once restricted in usebecause of propagation problems, the fern isnow being used in larger crop areas (figure 3),

Chinese use of azolla goes back hundreds ofyears, at least to the Ming dynasty, Its use inVietnam dates to the 1lth century. These twoare the only countries with a long history ofazolla cultivation. The practice probably beganwith recognition that the spontaneous growthof wild azolla in rice fields had a beneficial ef-fect on the crop. Organized use of the ferncould not occur, however, until reliable meth-ods were developed to overwinter and over-summer the fern. Since azolla can only begrown from vegetative material, it must be pro-

tected during seasons that are too severe forits survival.

The original sites of azolla cultivation arethought to have been Zhejiang Province inChina and Thai Binh Province in Vietnam. Un-til recently certain villages in these places hadtemples dedicated to the mythological dis-coverers of azolla. At the end of the 19th cen-tury azolla was being cultivated at favorablesites along the east Asian Coast as far southas 200 N latitude on the Red River delta in Viet-nam and northeastward through Guangdongand Fujian Provinces to Wenzhou District near280 N latitude in Zhejiang Province, China.

A major push for expanding the use of azollabegan in China and Vietnam in the early 1960s.Before that time it was common for certainfamilies or villages that had mastered the in-tricate techniques of oversummering and over-

Figure 3.—Geographic Distribution of Azolla

Distribution of Azolla species throughout the world, This distribution map is rapidly becoming outdated because many azollaspecies and varieties are being moved about and introduced into new places as research on azolla grows.

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wintering azolla to control the supply of azolla-starter-stocks in the spring. Peasants had totravel to these villages to purchase their springplants.

After the revolutions in China and Vietnam,the new governments eventually recognizedthe worth of azolla and began officially pro-moting its use and organizing the constructionof propagation centers.

During colonial days in Vietnam, Frenchscientists reported on the use of azolla and didsome preliminary research, but its cultivationwas never promoted officially. At the end ofthe colonial period, azolla was grown on about40,000 hectares1 as a green manure during thewinter for the spring rice crop. In 1958, thenew government established an azolla researchcenter at the Crop Production Research Insti-tute and set up an extension network with over1,000 inoculum production bases to stimulateuse.

Despite this promising beginning, the bigpush in azolla research did not come until theearly 1960s. Articles on azolla began appear-ing in 1962, culminating in several articles anda large book (9).

Since the introduction of high yielding ricevarieties to Vietnam in the early 1960s, mostazolla has been grown as a monocrop beforethe spring rice. The cultivated area reportedlydoubled from 1965 to about 700,000 hectaresin 1978. As in China, azolla cultivation in Viet-nam is seldom practiced in summer becausethe A. pinnata var. imbricata native to theAsian continent is sensitive to high tempera-tures and insects.

Vietnamese scientists have collected over 30varieties of local azolla and have selectedsuperior strains for heat, cold, salt, and acidtolerances. Despite these advances, reportedlymost communes and cooperatives have notadopted these improved azolla varieties.

The Chinese story is much the same as thatof Vietnam, although much more was knownof the Vietnamese experience because of the

‘ 1 hectare = 2.47 acres.

availability of publications in English andFrench as well as in Vietnamese. Recently, in-formation from China has become available(3,4,11,2,5).

Today, azolla is grown as a green manure onabout 1.3 million hectares of rice in China. Re-search and development activities have in-creased significantly, as have extension activ-ities to promote its use. Large posters have beenproduced to inform the public of azolla’s use-fulness and of its management requirements.

How Azolla Is Used as a Green Manure

Azolla can be used as a green manure (fig-ure

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4):

by growing it as a monocrop and then in-corporating it as a basal manure before therice is transplanted; or transported toanother site for use on upland crops;growing it as an intercrop and incorporat-ing it as a top dressing manure after therice is transplanted; orby growing it both as a monocrop and anintercrop.

All three systems can be successful but, asis common in agriculture, use of the greenmanure crop requires some adjustments inmanagement of both the green manure and themain crop.

Monocrop Azolla is used in China and Viet-nam during winter and spring to produce ni-trogen for the spring rice crop. The same tech-nique is used to produce nitrogen for the earlysummer rice crop, but this is less commonsince the growth of Azolla pinnata is affectedby high temperature and heavy pest attack dur-ing mid to late summer.

Intercropped Azolla is usually grown withthe rice in places where there is no time avail-able in the cropping system for the monocrop-ping of azolla. As an intercrop azolla will beinitially incorporated by hand or rotary riceweeder and then later killed by heavy shadingand/or high temperatures—with subsequentdecomposition and release of nitrogen to thecrop—at the stage of maximum rice tillering.

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F i g u r e 4 . — I n c o r p o r a t i n g A z o l l a I n t o S o i l

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Two of several methods for soils incorporating a monocrop of azolla as a basal green manure for rice. Both photos were takenduring the spring of 1980 in Guangdong province, China. The photo on the left is A. filiculoides, the photo on the right IS Azollaimbricata

The photo on the left shows an azolla beater being used to spread inoculum azolla after it was introduced into the field ofa second later summer rice crop to grow with the-rice as an intercrop.

The top center photo shows an azolla pusher which is used to spread inoculum azolla if it is applied to a rice crop after therice is transplanted, or is used to concentrate and collect azolla in a nursery. The bottom center photo shows a bamboo polebeing used to collect azolla growing in a canal.

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Growing both monocrop and intercroppedAzolla is a technique that is designed to usethe growing period for azolla before the plant-ing of the rice crop, plus production of addednitrogen for the crop through cultivation of in-tercropped azolla, In this system two differentvarieties of azolla may be used in each of thedifferent periods. Different temperature andlight sensitivities of azolla varieties make thispossible.

Who Is Doing Azolla Research?

A number of centers are conducting azollaresearch. Most of this work is less than 5 yearsold. Both China and Vietnam are studyingAzolla pinnata var. imbricata under their ownconditions. Recently, the Zhejiang Academy ofAgricultural Sciences has had an opportunityto evaluate the other Azolla species (caroli-nian, filiculoides, mexicana, microphyhlla,and nilotica) for use in China.

Many developing country rice researchcenters have begun azolla research, but withlittle success to date. Probably the most suc-cessful program is in Thailand, where the Min-istry of Agriculture has been sponsoring anazolla program that has progressed through theregional extension stations and has nowreached the stage of demonstration plots in thefields of progressive farmers.

The International Rice Research Institutestarted an azolla research program nearly 8years ago (10), IRRI is studying the use of sev-eral azolla species for use in flooded rice.

There are three major centers of azolla re-search in the United States. One is the Univer-sity of Hawaii, where agronomic and physiol-ogy studies are underway to characterize andunderstand the usefulness of all azolla speciesin tropical crop production systems, includingrice and taro (5). The work is led by T. A. Lum-pkin who was selected by the National Acad-emy of Sciences to conduct research on azollain the People’s Republic of China in 1979 and1980 at its foremost azolla research center, theZhejiang Academy of Agricultural Sciences atHangzhou.

Studying azolla management to fit temperate,broadcast-sown production systems is thefocus of the research program at the Univer-sity of California at Davis (8). Research objec-tives at UCD include use of A. filiculoides asa monocrop basal green manure crop forspringsown rice and A. mexicana as an inter-crop in rice. The UCD program received agrant from the USDA Competitive Grants Pro-gram in 1980 and a grant from the NationalScience Foundation.

Basic physiology studies are the focus of theprogram at the Kettering Laboratory focusedon understanding the Azolla/Anabaena rela-tionship (6). The program has been supportedby a grant from the National Science Founda-tion and a grant in 1979 from the USDA Com-petitive Grants Program.

Another azolla research program that weknow less about is at Virginia CommonwealthUniversity, where the isolation and reconstitu-tion of the Azolla/Anabaena association are be-ing studied. This work has been supported bya grant from the USDA Competitive GrantsProgram; the first grant was made in 1979. Dr.Jack Newton of the USDA in Peoria, Illinois,has done some research on isolation of Ana-baena from Azolla.

Countries that have initiated or plan to initi-ate azolla research include: India, Nepal, Thai-land, Bangladesh, Burma, Indonesia, Malaysia,The Philippines, Sri Lanka, Egypt, Peru, andthe West African Rice Development Associa-tion, headquartered in Liberia. In addition, sev-eral other countries have expressed an inter-est in the fern and its uses.

What Organizations Are FinancingAzoIla Research?

Current financial support for azolla researchin the U.S. comes from AID (a small 211(d)grant), the National Science Foundation (2grants), and the USDA (Section 406 and Com-petitive Grants). The USDA Competitive Grantsoffice has made three grants totaling $278,000to the University of California at Davis, Ket-

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tering Laboratory, and Virginia Common-wealth University. The National Science Foun-dation has made two grants: one each toUniversity of California at Davis and Ketter-ing Laboratory. In all probability, less than$300,000 per year is now being invested i nazolla research in the United States, The work

at Hawaii is sponsored by small 211(d) grantfor nitrogen fixation from the Agency for In-ternational Development and by a researchgrant from the U. S.D.A. under the Section 406program of the 1966 Food for Peace Act, andby Hawaii Agricultural Experiment Stationfunds,

AZOLLA’S EFFECT ON THE NEED FOR AGRICULTURAL INPUTS

Fertilizers

Successful cultivation of azolla requires theapplication of a certain amount of phosphorusfertilizer (0.5 to 1.0 kg p/ha/week), but this doesnot necessarily mean an increase in the amountof phosphorus fertilizer required to produce acrop of rice. The application of phosphorus isusually necessary for a good crop of rice, butinstead of applying it directly to the rice, thephosphorus can be given to the azolla first insmall weekly applications. Once the azolla isincorporated into the soil and begins to decom-pose, the phosphorus becomes available for therice crop. Thus phosphorus originally intendedfor the rice crop is first cycled through theazolla. The phosphorus enables the azolla togrow and fix nitrogen that will be used by therice. One kilogram of phosphorus applied toazolla results in the fixation of 5 kilograms ofnitrogen, North Vietnam is deficient in petro-leum products for the production of nitrogenfertilizer, but has sufficient phosphate depos-its to fuel its miniature azolla nitrogen fac-tories.

In certain deficient soils, azolla responds tothe applications of other nutrients such aspotassium, but these usually must also be ap-plied for a high yielding rice crop. In some raredeficient soils, the addition of small amountsof molybdenum and/or iron have proved usefulto increase azolla’s rate of nitrogen fixation.The Chinese often apply river mud, ash, andanimal manure to supplement the phosphorusgiven to azolla.

Pesticides

Azolla is attacked by larvae of several spe-cies of moths and midges and by certain kindsof snails and beetles. These pests are especiallydestructive during the summer season andmust be carefully controlled or the azolla canbe devastated. However, azolla is usually notcultivated on a large scale during the seasonswhen insects are rampant, but is maintainedin oversummering nurseries, In addition, evenwhen azolla is cultivated in the field during thesummer season, the pesticides normally usedon rice crops, such as diptenex, sumithion,malathion, and carbofuran are usually ade-quate for controlling azolla insects,

Irrigation

Azolla is a delicate, freefloating aquatic plant.Although it can last for months in a refrig-erator, it cannot survive for more than a fewhours on a dry soil surface under direct sum-mer sunlight, Since technology has not beendeveloped for the use of azolla seeds (spores)in cultivation, a small amount (1 to 10 percentof inoculation requirements) of azolla plantsmust be maintained through the seasons whenazolla is not being cultivated in the fields. Thismeans that in tropical and subtropical areas acertain amount of water must be availablethroughout the year either to maintain azollain nurseries or to cultivate it in the fields. Theoversummering maintenance of azolla shouldnot be a problem in regions where standing

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water is present throughout the year, such asin Bangladesh, or in regions where azolla canbe maintained in small nurseries beside moun-tain springs.

The period when irrigation is most criticalis when azolla is to be grown in the fields asa green manure. If azolla is cultivated as amonocrop before the rice, which is the mosteffective way, water must be available forflooding the fields. If water is not available,azolla cultivation will have to be delayed untilit can be grown as an intercrop with the rice.Azolla grows as an intercrop with rice duringthe first 20 to 30 days after transplanting. Inthis period, the paddy fields must remainflooded with at least a few centimeters ofwater, Although some species of azolla can sur-vive on mud, as is commonly seen in Hawai-ian taro fields, they need standing water forgood growth. Thus rice paddies dependentupon rain water , where short periods ofdrought often occur during the first month ofrice cultivation, will not be suitable for azollacultivation. Also, if extremely hot periods oc-cur when water temperatures exceed 400 C ,cooler water must be available for pumpinginto the fields to prevent the azolla from dy-ing of heat stress.

Even though azolla cultivation require someextra irrigation water, it must be rememberedthat in fields where little or no nitrogen fer-tilizer is used, the cultivation of azolla will sig-nificantly increase the efficiency of water use.If azolla increases the yield of rice from 2.5 tonsto 5 tons, then the efficiency of water use hasnearly doubled.

MachineryThe need for machinery is not a handicap to

successful azolla cultivation. Even the mostprimitive villages can manufacture the basictools required for the cultivation of azolla.These are made from such locally available rawmaterials as bamboo and wood. A simplemetal/wood tool, costing a few dollars, for in-corporating intercropped azolla into the soilcan be manufactured in villages by a black-smith. This tooI is not essential, but is more ef-ficient than soil incorporation by hand. Aneven more efficient multiple row incorporatingmachine, with a small gas engine, would haveto be manufactured commercially.

How Does Azolla Affect theProductivity of Tropical Soils?

Azolla affects soils in the same way as anyother nitrogen-fixing green manure. It contrib-utes nitrogen, which, after water, is the mostcommon limiting factor to higher crop yields.The application of nitrogen to increase cropyields is the cornerstone of the “green revolu-tion.” All new rice varieties are bred for highyielding response to nitrogen fertilizers.

The loss of organic matter is a primary causeof decreasing crop yields in the Tropics. A de-crease in soil organic matter results in soilstructure deterioration, lower plant nutrient re-serves from the organic matter, and a lower

cation exchange capacity. Cultivated tropicalsoil tend to have lower organic matter contentsand soil nitrogen than undisturbed tropicalsoils. This is especially true with Oxisols andUltisols.

What is the likelihood of Azolla widespreaduse? Azolla is cultivated as a green manure onabout 2 percent of the harvested rice area ofChina and about 5 percent of the spring ricecrop. In Vietnam, azolla is grown as a wintergreen manure for 8 to 12 percent of the coun-try’s total harvested rice area, and about 40 to60 percent of the irrigated spring rice in the

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Red River delta. Estimates of China’s terrestrialgreen manure crop (mostly legumes) are ashigh as 7 million hectares, or about five timesthe total estimated cultivation area of azolla.

As strains or species of azolla are found thatare less sensitive to high water temperaturesduring summer, the areas of azolla in Chinaand Vietnam will probably expand.

The major areas where azolla should proveuseful in rice production in the Tropics arethose where: 1) rice is transplanted, 2) labor isplentiful, and 3) some control of irrigationwater is possible. Also, countries with effec-tive research and extension services may havemore success with popularization of azolla.

Azolla technology is not applicable yet forareas where rice is broadcast-sown, except asa monocrop, preplant, basal green manure. Anazolla mat can suppress tiny, broadcast-sownrice seedlings; for that reason, intercroppedazolla will probably not be successful in broad-cast-sown rice unless it is inoculated in thefields after the rice seedlings have becomeestablished and are growing well above thewater surface.

With the above criteria in mind, the mostlikely countries to adopt azolla include partsof India, Bangladesh, Thailand, Indonesia,Philippines, Nepal, Peru, and the DominicanRepublic.

RESEARCH, DEVELOPMENT, AND IMPLEMENTATION PROGRAM

The Program Elements

Two basic azolla management systems needresearch attention; these are: 1) tropical, laborintensive systems; and 2) temperate, capital in-tensive systems, The tropical systems will befocused mainly on developing countries, andwill include these principles:

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labor intensive,land intensive,small farm based,crop intensive,maximizing opportunities for year-roundproduction,first priority to more intensive use of azollain transplanted rice systems, andsecond priority to use in broadcast-sownsystems.

The tropical program should set the follow-ing objectives:

1. To find azolla varieties that are less sen-sitive to high water temperatures (above27° C) and pest and disease attack. Thiswould have the effect of expanding azollause from its present primary role as aspring green manure and its secondaryrole as a fall green manure to the point

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3.

where it could be a primary green manurein summer in transplanted rice.To collect and characterize all of the sixknown azolla species, and to evaluatethem for use year-round in tropical trans-planted rice production systems. [Note: in1980 preliminary studies by Lumpkin andhis Chinese co-workers in China, A. micro-phylla shows great promise as a summergreen manure in south Central China, anda winter green manure in the south. Also,A. nilotica shows promise as a fall greenmanure in China. Neither of these specieshas ever been tested in rice before. Furthermission-oriented research could have highpayoff in the near future.]After characterization and early testing,distribute promising strains to - nationalprogram centers for synthesis, design, andtesting of new rice cropping systems basedon azolla as a green manure.

Temperate, capital-intensive rice productionsystems, primarily centered on broadcast-sownor drill-sown rice. This work should focus ondeveloped countries, and on middle-incomecountries (e.g., Brazil and Colombia, and othercountries, primarily in Latin America wheresimilar rice production systems are used).

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What Organizations Should BeInvolved?

In the United States there are two placeswhere azolla is being studied for use in agri-culture. The University of California at Davisis conducting research on azolla for use intemperate zone, broadcast-sown rice, andwould be the logical leader for the temperaterice work, The University of Hawaii has a pro-gram on evaluation of azolla for use in tropi-cal production systems, and would be thelogical leader for the tropical efforts. Ketter-ing Laboratory, Virginia Commonwealth Uni-versity and USDA have specialized programsthat could play supporting basic research rolesfor the temperate and tropical programs.

Links to developing countries will be neces-sary. Important programs elsewhere includethe Zhejiang Academy of Agricultural Sciences,Hangzhou People’s Republic of China, (theUniversity of Hawaii has a cooperative pro-gram there already); the Fujian Province, PRC(IRRI has links with this group); IRRI, and na-tional programs in Thailand, India, and Nepal.Several national research programs were ini-tiated after an FAO-sponsored azolla trainingmission by T. A. Lumpkin in 1977. Also T. A.Lumpkin and J. L. Walker of the University ofHawaii, on behalf of the Inter-American De-velopment Bank, visited Uruguay, Brazil, Peru,and Colombia in 1979 to assess the potentialfor azolla in those countries.

The West African Rice Research and Devel-opment Association (WARDA) is also inter-ested in establishing an azolla research pro-gram, and they should be tied into the tropicalnetwork,

What Is the Necessary Level ofFinancial Support?

We will speak first of priority areas of re-search. There is need to carry out severalpriority activities soon. These include:

c More extensive and complete collection ofazolla species and varieties for evaluationin agriculture. Indeed, collection shouldtake precedence over efforts to breed

azolla because the array of variability avail-able in nature is clearly great, and thisshould be collected and characterizedbefore beginning breeding programs.Characterization of azolla varieties as totolerance of high and low temperature,phosphorus levels in water, pH, light, andother growing conditions should be of highpriority.Testing and fitting existing azolla varietiesinto rice production systems should re-ceive high priority.

These three priority areas should receive firstattention for funding. Related basic researchon physiology of the Azolla/Anabaena sym-biosis, biochemistry of the association, etc., canprobably be funded through basic researchgrants from NSF or USDA.

The applied aspects of collection, character-ization for use in agriculture, and fitting intorice production systems could be done for theTropics for about $400,000 to $600,000 peryear. This would allow funds for collaborativecollecting trips to assemble a wider germplasmbase, to conduct screening trials for toleranceto the physical and growing environment, andto run first assessments of potential usefulnessin production systems. Such funding wouldalso allow some limited funds for working withcollaborators in a tropical azolla network, Itwould be desirable to have some funds forassisting, through small subgrants, the conductof specific desired research programs in coop-erating countries.

Training, both nondegree and degree, shouldreceive attention early in the program. The firsttraining should emphasize azolla research tech-niques (e.g., many programs have failed be-cause researchers did not know how to keepazolla alive during hot or cold weather). Later,training could begin to stress field manage-ment, We believe the general principle to fol-low in funding azolla research is probably thatcontinuity of funding over the first severalyears will be more effective than heavy fund-ing over a shorter time. Collecting, characteriz-ing, and evaluating production systems needsto be done by a team that will require continu-ity for effectiveness. Such a team should in-

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elude an algologist or cyanobacteria specialist.It should have access to laboratory, green-house, and field facilities. The tropical leadinginstitution should be able to grow azolla in thefield at any time of the year, and to grow azollain such a way that all growth stages can beavailable at any time.

The temperate program will probably requirefunding in the same order of magnitude as thetropical program. The temperate network maybe easier to establish because: 1) the potentialcountries involved are either in the developedor middle income categories and therefore mayhave more resources at their disposal, and 2)the countries’ institutional research capacitywill be much stronger than those of the tropi-cal LDCs.

Some savings may be made and efficiencygained through close cooperation between thetemperate and tropical programs. Joint collec-tion trips and close adherence to jointly—determined protocols for testing and evalua-tion within the networks should save both timeand funds.

What Are the Personnel Requirements?

We believe the major research networksshould be oriented toward practical adaptationof azolla to agricultural production. Therefore,agronomists with strong physiology and fieldproduction backgrounds will be required, Aswas previously stated, specialists in blue-greenalga should be available in the parent institu-tion or nearby.

The program should provide for laboratoryand greenhouse assistance, as well as fieldworkers for the field experiments, It is prob-able that some of this work may be providedby graduate students and student help and byexisting institutional farm staff, but some full-time assistance will be needed.

Research assistantships should be providedin the program; this will get the training pro-gram going as early as possible.

What Are the Attitudes of ThoseWho Would Be Affected?

Most research organizations have becomeaware of azolla and have some idea as to itspotential. A few extension specialists (notablyin rice) probably also know something aboutit. Beyond that, except in China and Vietnamand a few individuals in developed countries,the farmers would know nothing of the plantand its potential use in rice. It may be that sinceazolla is already used successfully in China andVietnam i t may be easier to popularizeelsewhere.

What Are Conducive Conditions forImplementation of the Technology?

Conditions conducive to azolla use in theTropics include:

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transplanted rice;rural labor supply;assured water supply and some control ofwater; andalso, for now, places that grow spring orlate summer/fall rice crops because of thehigh temperature susceptibility of A. pin-nata in summer.

For rice in temperate zones, the conduciveconditions are much less certain because suc-cess has not yet been conclusively demon-strated. Factors thought to be important forbroadcast-sown rice include:

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growing cold-tolerant azolla (e.g., A .filiculoides) as a monocrop green manureto be incorporated into the soil beforesowing;growing heat-tolerant, shade-sensitiveazolla as an intercrop with the broadcastsown rice during the summer; andhaving an assured source of water to growthe monocrop azolla before planting ofrice.

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Where Do Conducive Conditions Existand Where Are They Likely to Develop?

Most of the countries of Asia have conduciveconditions for use of azolla. Special oppor-tunities for success seem to be present in Thai-land, Bangladesh (aus crop), and the Philip-pines (irrigated dry season crop). In LatinAmerica, Peru and the Dominican Republic ap-pear to have the proper rice production sys-tems to make Azolla use a possibility.

What IS the Sequence of Steps Leadingto Successful Implementation?

The first two things a country must learn todo are how: 1) to keep azolla plant materialsalive year-round and 2) to multiply azolla stocksin order to have inoculant materials availablefor use in the rice crop. Principles for suchtechniques can be learned in training programsat the network headquarters or azolla researchcenters. Such techniques need to be taughtwidely to extension workers and to innovativefarmers.

In some conditions in Asia, A. pinnata, A.pinnata var . imbr icata and perhaps A .filiculoides could be used now as a monocropbasal fertilizer before transplanting of rice.This should be easy to popularize for the latewinter or early spring rice crops.

Before azolla is used in rice, however, itshould be tested under local conditions. As wasstated, keeping azolla alive throughout the yearand finding ways to multiply it for field use arethe most important steps in beginning a pro-gram. The next step is testing under local con-ditions to find ways to fit it into the existingproduction system. Use as a basal fertilizerbefore transplanting is probably easiest, but ifthe crop cycle doesn’t allow time to grow anazolla green manure crop between rice crops,then it will be necessary to grow it as an inter-crop. In that case the rice must be grown inrows so that incorporation of the azolla can bedone. This is just an illustration of some of theconsiderations to be dealt with in using azollain agricultural production systems.

CONSTRAINTS TO THE DEVELOPMENT AND IMPLEMENTATIONOF AZOLLA TECHNOL0GY

Scientific Constraints

The global azolla research effort is disorga-nized and much of the work is repetitious andoften useless. Certain problem areas, such asthose involving agricultural engineering, havebeen ignored. Much of the support is going tofinance esoteric work, while many of the peo-ple doing the research have little understand-ing of the problems that prevent azolla’s wide-spread use by peasant farmers. Much of thework is involved in trying to improve labora-tory specimens of azolla, while the vast dif-ferences in wild varieties remain unexamined.

Many of the problems preventing the wide-spread use of azolla require a multidisciplinaryresearch approach, but so far azolla researchhas been cloistered into individual depart-ments, even in the international institutes.

Funding agencies can assist in ensuring thatazolla research will be directed toward realproblems and needs by requiring multidisci-plinary, linked efforts that focus on use ofazolla on farms. This does not mean that basicresearch will be precluded, but it will ensurethat practical, mission-oriented research willnot be neglected.

Environmental Constraints

Water is the primary environmental con-straint to the cultivation of azolla. Azolla is afreefloating aquatic fern and is therefore lim-ited to locations that have an abundant, stablewater supply during field cultivation.

Temperature and humidity: For practicalpurposes, azolla survives within the water tem-perature range of O to 400C; beyond this range,

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death will result, For adequate growth duringfield cultivation, the daytime water tempera-ture should stay within the range of 15° to35 ‘C. Humidity and temperature interact intheir effect on azolla. Very high humidity andhigh temperature or very low humidity and lowtemperature are both detrimental to the growthof azolla.

pH: The pH of the paddy water plays an important part in the ability of azolla to surviveBesides directly affecting the growth of azolla,pH also affects the availability of nutrients,especially phosphorus. Low pH and high pHcan cause formation of insoluble compoundsthat tie up available phosphorus; the phos-phorus in such insoluble compounds is un-available to azolla. Azolla grows best within apH range of 5 to 7 and can survive a range of3.5 to 10.

Available nutrients: Azolla growth dependson an adequate supply of essential elements inthe water or in the surface layer of mud. Theseelements must also be relatively balanced, Usu-ally the addition of phosphorus and sometimespotassium is all that is necessary to ensuregood growth.

Cultural and Economic Constraints

For most farmers, azolla cultivation wouldbe an entirely new way of using green manure.The idea of using an aquatic plant for such pur-poses is not part of most agricultural heritages,Farmers in tropical Asia traditionally havegrown upland legume crops, such as milk vetchor lentils (as a cash crop), after harvesting themonsoon rice crop. Most have never grown anaquatic green manure, and many have rarelygrown a legume that is not a food or foragecrop. To some, especially the hungry, growinga crop that is to be plowed under as a greenmanure may seem impractical.

Azolla can be used as a forage for pigs,ducks, and fish. However, the raising of swine,ducks, and fish is uncommon in some places.Also, it is generally believed, although untested,that cattle and water buffalo will not eat azolla.

The year-round cultivation of azolla is morecomplex than the cultivation of rice. Withoutsupport, many poor uneducated rice farmersprobably would not or could not grow azolla,Diligent rice farmers, such as those in Nepalor Thailand, probably could master azollacultivation techniques, just as farmers in Chinaand Vietnam have. As a result of unfavorableland ownership patterns, low grain prices, andother social or economic difficulties, somepeasant rice farmers do little more than hap-hazardly plant their fields and then wait forharvest time. For them, meticulous farmingdoes not yield sufficient benefits to their family,Furthermore, transplanted rice in some partsof Asia is not planted in rows, a necessarymeasure for azolla to be incorporated as a basalfertilizer.

Also, many farmers who could not be con-vinced to use nitrogen fertilizer in the 1960swhen it was inexpensive, will be unlikely tocultivate azolla. The exceptions might be peas-ant farmers who want to improve their cropyields but do not have the capital to purchasenitrogen fertilizers. Also, farmers who havegiven up using nitrogen fertilizer because ofthe high cost might be convinced to use azollaas long as they can afford the cash outlay forrelatively small amounts of phosphorus fer-tilizer and pesticides. They would have to pur-chase about 100 kg of single superphosphateto grow one hectare of azolla for 4 to 5 weeks.If properly applied, the phosphorus would re-sult in as much nitrogen as 500 kg of commer-cial ammonium sulfate fertilizer,

Azolla cultivation could significantly reducethe fertilizer input costs of raising high yieldingrice crops, but would still require the purchaseof certain inputs, especially phosphorus fer-tilizer. Farmers unable to obtain these inputswould probably find it difficult or impossibleto raise azolla.

Political Constraints

The widespread cultivation of azolla is foundonly in Communist countries. Azolla wascultivated in both China and Vietnam before

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the present governments came to power, buton only a small fraction of the area that azollacovers today. Analyzing the elements of thissituation is difficult because the cultivation ofazolla in China and Vietnam cannot be com-pared to its cultivation in countries with dif-ferent political systems. Because azolla cul-tivation is just being introduced to farmerselsewhere, there has been insufficient time forother countries to develop successful azollaprograms that are in line with their politicalsystems.

Even without an adequate comparison, it isobvious that the successful azolla programs inChina and Vietnam owe a considerable amountto the way their farming systems are organized.The commune and cooperative organizationsof these countries that use azolla have highly

trained azolla teams, whose sole function is toensure the success of azolla cultivation. Train-ing workshops to learn the newest techniquesare held annually from the national level downto the local azolla team level. In addition, everylevel regularly publishes pamphlets about thepractical applications of azolla.

The higher levels of the Chinese and Viet-namese systems can be transferred with minormodifications to other countries, but not thelower local levels. Most governments do nothave the power to enforce their will on inde-pendent peasant farmers as effectively as Chinaand Vietnam can influence their communesand cooperatives. Nor can a peasant farmer beexpected to master all the intricacies of suc-cessful azolla cultivation that are known by ahighly trained commune azolla team.

THE EFFECT OF THE IMPLEMENTATION OF AZOLLA TECHNOLOGY ONTHE NEED FOR INPUTS

capital

Capital requirements for azolla cultivationare quite small. For most farmers, only a smallamount of phosphorus fertilizer, often no morethan would be required for the rice crop, andpesticides to protect the azolla from pests anddiseases are all that will be required.

Farm Labor

In essence, the cultivation of azolla ex-changes labor for nitrogen fertilizer. The pres-ent azolla technology is based on the Chineseand Vietnamese models and thus is extremelylabor intensive. In fact, the cultivation of azollacannot be adopted by countries with mech-anized rice farming systems until new capitalintensive technology is developed.

Adoption of azolla cultivation by a develop-ing country can only increase the demand forfarm labor, especially when nursery stocks arebeing multiplied and during field cultivation.In addition, a few workers will have employ-

ment year-round because of the need to main-tain azolla nurseries during the off season.

Rice requires about 20 kg of nitrogen per tonof the harvested crop. About half of this isrecycled into the soil in the crop residue; there-fore about 10 kg of nitrogen is removed per tonof harvested grain. A 6 ton rice harvest re-moves about 60 kg of nitrogen from the soil,equivalent to 300 kg of ammonium sulfate fer-tilizer. If azolla was substituted for ammoniumsulfate, nearly all of the money required to pur-chase the 300 kg of ammonium sulfate fertilizercould theoretically be used to pay farm laborto grow azolla, or to gain a greater return onfamily labor.

Azolla appears to offer special opportunitiesfor small farms, particularly family farms withabundant labor. Conversely, suitable azollatechnology for large mechanized farms is notavailable.

Azolla is used successfully on large com-munes in China, but the organization of thesecommunes is difficult to relate to family farms.

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Land

The land required for azolla cultivationmainly is related to nursery and field multi-plication. For overwintering or oversummer-ing, very small protected greenhouse or fieldareas are required, more in the area of smallgarden plots than large field areas. However,when azolla multiplication for field inoculationis to be achieved, much more land is required.Perhaps as much as 10 percent of the rice croparea to be inoculated is a good estimate of theland area needed for azolla field multiplication.This land is not tied up permanently, however,but it will be devoted to azolla multiplicationfor a month or so prior to inoculation.

For farming systems that use azolla as abasal, soil incorporated green manure beforethe rice crop, all of the land to be planted intorice and fertilized with azolla will need to bedevoted to azolla cultivation for about a monthprior to transplanting.

In situations where azolla is used as a soil-incorporated, top-dressed green manure or asan unincorporated intercrop with rice, no landwill be required to be devoted solely to azolla,except for the inoculation nurseries.

CONCLUSIONS

Azollanitrogen

is being used as a primary source ofon an increasing land area in trans-

planted rice crops in China and Vietnam. Thelargest use of azolla in these countries is in thespring rice crop, mostly as a monocrop grownbefore rice as a basal, soil-incorporated greenmanure. Less is used as an intercropped top-dressing green manure in transplanted rice thatis planted in rows.

Use of azolla in the summer rice crop is ham-pered by high water temperatures and heavypest attack. A search for suitable temperature-tolerant species or varieties could have highpayoff.

Species used in agriculture today are: A. pin-nata, A. pinnata var. imbricata (sometimes re-ferred to as A. imbricata, and A. filiculoides.A. pinnata and imbricata have been used fora long time in China and Vietnam, but theirsusceptibility to high temperatures and pest at-tack makes them suitable only for spring andsome fall rice crops. A. filiculoides has justbegun to be used widely in China, especiallyin areas where-because of its cold tolerance—it can be grown in late winter and early springas a green manure for early spring rice. Al-though A. filiculoides has proved useful inChina because of its cold tolerance, it is evenless tolerant of high water temperatures (above

250 to 270 C) than A. pinnata. Whatthen, is an azolla that can toleratemer temperatures, up to 400 C

is needed,high sum-or so. A .

microphylla, collected by T. Lumpkin in theGalapagos Islands, shows promise of becom-ing a suitable summer green manure for cen-tral China and a winter green manure in southChina.

There is a great need to collect and char-acterize species and varieties of azolla extantin nature. This work is of the highest priority.The potential worth of A. microphylla in Chinahas already been mentioned. However, it maybe useful to point out that A. nilotica, collectedby T. Lumpkin in the Sudan, has shown thehighest nitrogen fixation of any azolla studied.Lumpkin was only able to collect three speci-mens of A. nilotica, yet many more strains andtypes are available in the Nile Basin and theseshould be collected and characterized as soonas possible.

All species could prove useful. For example,varieties of filiculoides look promising now foruse in certain agricultural situations. The samecan be said about microphylla, imbricata, pin-nata, and caroliniana.

Research programs should stress multidisci-plinary approaches, with close links between

38-846 0 - 85 - 5

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institutions. Both tropical and temperate farm-ing systems should be emphasized, but theseprograms should be centered in differentplaces. Both temperate and tropical researchprograms should be linked, and should coop-erate in collection and characterization of spe-cies and varieties. The tropical program shouldfocus on using azolla in tropical farming sys-tems, notably small peasant farms, and thetemperate program should focus on capital in-tensive mechanized rice production systems.An international meeting should be held thatwill have as its major agenda item the settingof international research priorities for azolla.The primary focus of research programsshould be to find a useful role for azolla infarming systems. Basic research should not beneglected, but the potential usefulness of azollais too great to delay its wider use in agricul-ture through emphasis on more esoteric topicsat the expense of applied research.

1.

2,

3.

4.

References

Dolbert, Frands, DANIDA, personal communi-cation, 1980.Food and Agriculture Organization, China:Azolla propagation and small-scale biogas tech-nology, Food and Agriculture Soils Bull. No. 41,FAO, Rome, 1978.Guandong Academy of Agricultural Science,Red Azol]a (People’s Publisher, Guandong (inChinese), 1975).Guandong Bureau of Agriculture, Questionsand Answers Concerning Azolla Cultivation

5.

6.

7,

8.

9.

10,

11

12.

13.

14,

(People’s Publisher, Guandong (in Chinese),1975),International Rice Research Institute, Interna-tional Bibliography on Azolla, IRRI (Los Ganos,Philippines, 1979), 66 pp.Lumpkin, T. A., “Environmental Constraints toAzolla Cultivation, ” Proc. Second ReviewMeeting I.N.P. U.T.S. Project (Honolulu, Ha-waii, May 18-19, 1978), pp. 175-180.Lumpkin, T. A, and Plucknett, D. L., “Azolla:Botany, Physiology, and Use as a Green Ma-nure,” Econ. Bet. 34(2): 111-153, 1980.Moore, A. W., “Azo]la: Biology and AgronomicSignificance, ” Bet. Rev. 35: 17-35, 1969.Peters, G. A., “The Azolla-Anabaena Sym-biosis,” In: Alexander Hollaender (cd.), GeneticEngineering for Nitrogen Fixation (PlenumPress, New York and London, 1977), pp. 231-258.Singh, P. K., “Use of Azolla in Rice Productionin India,” In: Nitrogen and Rice (InternationalRice Research Institute, Philippines, 1980), pp.407-418.Talley, S. N., and Rains, D. W., “Use of Azollain North America, ” In: Nitrogen and Rice (In-ternational Rice Research Institute, Philippines,1980), pp. 419-431.Vo, M. K, am-l Tran, Q. T., Beo Hoa Dau ~Azo)la)(Agricultural Publisher, Hanoi, 1970), 171 pp.Watanabe, I., Espinas, C. R., Berja, N. S., andAlimagno, V. B., “Utilization of the Azolla-Anabaena Complex as a Nitrogen Fertilizer forRice,” International Rice Research Institute,Res. Paper Ser. No, 11, 1977.Zhejiang Academy of Agricultural Science,Cultivation, Propagation and Utilization ofAzolla (Agricultural Publishing House, Beijing(in Chinese]. 1975).

Chapter VIII

Using Zeolites in Agriculture

Frederick A. MumptonDepartment of the Earth Sciences

State University CollegeBrockport, NY 14420

ContentsP a g e

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 127Natural Zeolites . . . . . . . . . . . . . . . . . . . . . . . . 127Chemistry and Crystal Structure of

Zeolites . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128Properties of Zeolites. . . . . . . . . . . . . . . . . . 129

Applications in Agronomy ......,,.,.. . . . 133Fertilizer and Soil Amendments . . . . . . . . 133Pesticides, Fungicides, Herbicides. ,,.... 135Heavy Metal Traps . . . . . . . . . . . . . . . . . . . 135

Applications in Animal Husbandry . . . . . . . 136Animal Nutrition . . . . . . . . . . . . . . . . . . . . . 136Poultry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136Swine . . . . . . . . . . . . . . . . . . . . . . .+....... 136Ruminants . . . . . . . . . . . . . . . . . . . . . . . . . . . 139Excrement Treatment . . . . . . . . . . . . . . . . . 141Malodor and Moisture Control . . . . . . . . . 141Methane Purification. . . . . . . . . . . . . . . . . . 142

Aquacultural Applications . . . . . . . . . . . . . . . 143Nitrogen Removal From Closed or

Recirculation Systems . . . . . . . . . . . . . . . 143Aeration Oxygen Production . . . . . . . . . . . 144Fish Nutrition . . . . . . . . . . . . . . . . . . . . . . . . 144

Occurrence and Availability of NaturalZeolites .....,...,,.. . . . . . . . . . . . . . . . 144

Geological Occurrence. . . . . . . . . . . . . . . . . 144Geographic Distribution . . . . . . . . . . . . . . . 146Mining and Milling . . . . . . . . . . . . . . . . . . . 149

Discussion, ..,,.... . . . . . . . . . . . . . . . . . . . . 150Agronomic Applications . . . . . . . . . . . . . . . 150Animal Nutrition Applications ., ..,.,.., 151Excrement Treatment Applications . . . . . . 152

Conclusions and Recommendations . . . . . . . 152References .,.. . . . . . . . .,..,..+, . . . . . . . 155

Tables

Table No. Pagel. Representative Formulae and Selected

Physical Properties of ImportantZeolites . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

2. Growth Response of Radishes toAmmonium-Exchange Clinoptilolite . . . . 134

3, Growth Response of Radishes toNatural Clinoptilolite Plus Urea ,....., 134

4. Caloric Efficiencies of ZeoliteSupplements in Poultry Feeding . . . . . . . 136

5. Apparent Caloric Efficiency of Zeolitein Chicken Rations . . . . . . . . . . . . . . . . . . 137

6. Caloric Efficiency of ZeoliteSupplements in Swine Feeding . . . . . . . . 137

7. Effect of Zeolite Diets on Healthof Swine . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

8. Effect of Prenatal Zeolite Diet onNewborn Pigs, .,, . . ., ..,,.,.., ..,.,. 138

9. Effect of Zeolite Supplementing theDiets of Early Weaned Pigs . . . . . . . . . . . 139

10.

11.

12.

13.

14.

15.

16.17.

18.

19.

Effect of Zeolite Supplement inMolasses-Based Diets of Young Pigs .,. 139Effect of Clinoptilolite Supplementalin the Diet of Swine . . . . . . . . . . . . . . . . . 140Occurrence of Diarrhea and Soft-FecesAmong Calveson Diets SupplementedWith 5% Clinoptilolite . . . . . . . . . . . . . . . 141Effect of Zeolite Additions to ChickenDroppings . . . . . . . . . . . . . . . . . . . . . . . . . . 142Effect of Clinoptilolite Additions to theDiet of Trout . . . . . . . . . . . . . . . . . . . . . . . 144Reported Occurrences of SedimentaryZeolites . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148Countries Engaged in Zeolite Mining . . 150Organizations Engaged in Zeolite/Agronomic Investigations . . . . . . . . . . . . 151Organizations Engaged in AnimalNutrition Studies Using Zeolites . . . . . . . 152Zeolite Property Holders andZeoagricultural Research Efforts. ..,,,. 153

Figures

FigureNo. Pagel. Simple Polyhedron of Silicate and

. .

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.12.

Aluminate Tetrahedra . . . . . . . . . . . . . . . . 130Arrangements of Simple Polyhedra toEnclose Large Central Cavities .., ...,, 130Solid Sphere Models of SyntheticZeolite and Chabazite . . . . . . . . . . . . . . . . 131Stylized Illustration of the Entry ofStraight-Chain Hydrocarbons andBlockage of Branch-Chain Hydrocarbonsat Channel Apertures ,, ......,,,,,,., 131Langmuir-Type Isotherm for Adsorptionon Crystalline Zeolites IllustratingAlmost Complete Saturation at LowPartial Pressures of the Adsorbate ,,... 131Types of Ion-Exchange Isotherms for theReaction As + BZ = AZ + Bs, . . . . . . . . . 132Change of Soil Nitrogen of Paddy SoilWith Time . . . . . . . . . . . . . . . . . . . . . . . . . 133Yield of Chrysanthemums as a Functionof Potassium Level Supplied by One-TimeAdditions of Clinoptilolite . . . . . . . 134Cumulative Leachate NO3-N for BandedNH4-Exchanged Clinoptilolite andBanded Ammonium Sulfate ..,,,,,. . . . 135Methane-Purification System, PalesVerde Landfill . . . . . . . . . . . . . . . . . . . . . . 142Field Exposure of Zeolite Beds ,,, ,,,.. 145Scanning Electron Micrograph ofClinoptilolite Laths With Minor MordeniteFrom a Saline-Lake Deposit Tuff NearHector, CA . . . . . . . . . . . . . . . . . . . . . . . . . 146

Chapter Vlll

Using Zeolites in Agriculture

AS agriculturalists the world over increasetheir effort to expand crop and animal produc-tion, more and more attention is being paid tovarious mineral materials as soil amendmentsand as dietary supplements in animal hus-bandry. The close relationship between theagricutura1 and geological sciences is notnew--crop production depends on the exist-ence and maintenance of fertile soil andagronomists rely on knowledge of mineralogyand geochemist}’ of clays and other soil con-stituents. In the animal sciences, the additionof crushed limestone to chicken feed tostrengthen egg shells is well known, as is theuse of bentonite as a binding agent in pelletizedanima1 feed stuffs.

Recently, one group of minerals has emergedas having considerable potential in a wide va-riety of agricultural processes. This group ofminerals is the zeolite group. The unique ion-exchange, dehydration-rehydration, and ad-sorption properties of zeolite materials prom-ise to contribute significantly to many years ofagricultural and aquacultural technology (60).

Most of the initial research on the use of zeo-lites in agriculture took place in the 1960s inJapan, Japanese farmers have used zeolite rockfor years to control the moisture content andmalodor of animal wastes and to increase thepH of acidic volcanic soils. The addition ofsmall amounts of the zeolites clinoptilolite andmordenite to the normal protein diet of pigs,chickens, and ruminants gave noticeable in-

Zeolites are crystalline, hydrated aluminosil-icates of alkali and earth metals that possessinfinite, three-dimensional crystal structures.They are further characterized by an ability tolose and gain water reversibly and to exchange

creases in the body weight and general “health”of the animals (52). The use of zeolites in ra-tions also appeared to reduce odor and asso-ciated pollution problems and to provide ameans of regulating the viscosity and nitrogenretentivity y of animal manure. These same zeo-lites were also found to increase the ammoni-um content of rice paddy soils when addedwith normal fertilizers.

Although most of these were preliminary re-sults and often published in rather obscurejournals or reports from local experiment sta-tions, they did suggest that zeolites could actas traps or reservoirs for nitrogen both in thebody and in the soil. The growing awarenessof such phenomena and of the availability ofinexpensive natural zeolites in the WesternUnited States and in geologically similar partsof the world has aroused considerable commer-cial interest. Zeolites are fast becoming the sub-ject of serious investigation in dozens of agri-cultural laboratories both here and abroad.Some of the ways in which zeolites can con-tribute to more efficient crop and livestock pro-duction are discussed below, along with theirrole in the rapidly expanding areas of fishbreeding and aquiculture. At this stage, thenumber of published papers dealing with “zeo-agriculture “ is quite small, and hard data arefew; however, the potential of these materialsin such areas is apparent, and zeolites showpromise of contributing directly to increasedagricultural productivity in the years to come.

ZEOLITES

some of their constituent elements without ma-jor change of structure. Zeolites were discov-ered in 1756 by Freiherr Axel Fredrick Cron-stedt, a Swedish mineralogist, who namedthem from the Greek words meaning “boiling

127

128

stones, “ in allusion to their peculiar frothingcharacteristics when heated before the miner-alogist’s blowpipe. Since that time, nearly 50natural species of zeolites have been recog-nized, and more than 100 species having nonatural counterparts have been synthesized inthe laboratory. Synthetic zeolites are the main-stays of the multimillion-dollar molecular sievebusinesses that have been developed by UnionCarbide Corp., W. R. Grace& Co., Mobil Corp.,Norton Co., Exxon Corp., and several othercompanies in the last 25 years in the UnitedStates and by chemical firms in Germany,France, Great Britain, Belgium, Italy, Japan,and the Soviet Union.

Natural zeolites have long been known tomembers of the geological community as ubiq-uitous, but minor constituents in the vugs andcavities of basalt and other traprock forma-tions. It was not until the late 1950s that theworld became aware of zeolites as major con-stituents of numerous volcanic tuffs that hadbeen deposited in ancient saline lakes of theWestern United States or in thick marine tuffdeposits of Italy and Japan. Since that time,more than 2,000 separate occurrences of zeo-lites have been reported from similar sedimen-tary rocks of volcanic origin in more than 40 countries. The high purities and near-surfacelocation of the sedimentary deposits has

prompted intense commercial interest bothhere and abroad. Many industrial applicationsbased on the exciting bag of chemical and phys-ical tricks of zeolites have been developed.

The commercial use of natural zeolites is stillin its infancy, but more than 300,000 tons ofzeolite-rich tuff is mined each year in theUnited States, Japan, Bulgaria, Hungary, Italy,Yugoslavia, Korea, Mexico, Germany, and theSoviet Union. Natural zeolites have found ap-plications as fillers in the paper industry, aslightweight aggregate in construction, in poz-zolanic cements and concrete, as ion-exchang-ers in the purification of water and municipalsewage effluent, as traps for radioactive spe-cies in low-level wastewaters from nuclear fa-cilities, in the production of high purity oxy-gen from air, as reforming petroleum catalysts,as acid-resistant absorbents in the drying andpurification of natural gas, and in the removalof nitrogen compounds from the blood of kid-ney patients (58).

The applications and potential applicationsof both synthetic and natural zeolites depend,of course, on their fundamental physical andchemical properties. These properties are inturn related directly to the chemical composi-tion and crystal structure of individual species.

CHEMISTRY AND CRYSTAL STRUCTURE OF ZEOLITES

Along with quartz and feldspar, zeolites are tassium (K+) elsewhere in the structure. Thus,“tektosilicates, ” that is, they consist of three- the empirical formula of a zeolite is of the type:dimensional frameworks of silicon-oxygen( S i O4)

4 tetrahedral, wherein all four cornerM 2/ nO . Al2O a . xSiO2 ● y H2O

oxygen atoms of each tetrahedron are shared where M is any alkali or alkaline earth element,with adjacent tetrahedral. This arrangement of n is the valence charge on that element, x issilicate tetrahedral reduces the overall oxygen: a number from 2 to 10, and y is a number fromsilicon ratio to 2:1, and if each tetrahedron in 2 to 7. The empirical and unit-cell formulae ofthe framework contains silicon as its central clinoptilolite, the most common of the naturalatom, the structures are electrically neutral, as zeolites, is:is quartz (SiO2. In zeolite structures, however, (Na,K)2O . Al2O 3 ● 1 0 S i O2 ● 6 H2O orsome of the quadrivalent silicon is replaced bytrivalent aluminum, giving rise to a deficiencyof positive charge. This charge is balanced by Elements or cations within the first set of pa-the presence of mono- and divalent elements rentheses in the formula are known as ex-such as sodium (Na +), calcium (Ca2 + ), and po- changeable cations; those within the second set

129

of parentheses are called structural cations, be-cause with oxygen they make up the tetrahe-dral framework of the structure. Loosely boundmolecular water is also present in the struc-tures of all natural zeolites, surrounding the ex-changeable cations in large pore spaces.

Whereas the framework structures of quartzand feldspar are dense and tightly packed,those of zeolite minerals are remarkably openand void volumes of dehydrated species asgreat as 50 percent are known (table 1). Eachzeolite species has its own unique crystal struc-ture and, hence, its own set of physical andchemical properties. Most structures, however,can be visualized as SiO4 and AlO4 tetrahedrallinked together in a simple geometrical form.This particular polyhedron is known as a trun-cated cube-octahedron. It is more easily seenby considering only lines joining the midpointsof each tetrahedron, as shown in figure 1.

Individual polyhedra may be connected inseveral ways; for example, by double four-ringsof oxygen atoms (figure 2a), or by double six-rings of oxygen atoms (figure 2b), the frame-work structures of synthetic zeolite A and themineral faujasite, respectively. Solid-spheremodels of synthetic zeolite A and of the mineralchabazite are illustrated in figures 3a, 3b.

once the water is removed from a zeolite,considerable void space is available withinboth the simple polyhedra building blocks andthe larger frameworks formed by several poly-hedra. Although water and other inorganic andorganic molecules would appear to be able tomove freely throughout a dehydrated zeoliteframework, the passageways leading into thesimple polyhedra are too small for all but thesmallest molecules to pass; however, ports orchannels up to 8 A in diameter lead into thelarge, three-dimensional cavities (figures 2a, 2b,3a, 3b).

Properties of Zeolites

Adsorption properties: Under normal condi-tions, the large cavities and entry channels ofzeolites are filled with water molecules form-ing hydration spheres around the exchange-able cations. Once the water is removed, usual-ly by heating to 3000 to 4000 C for a few hours,molecules having diameters small enough tofit through the entry channels are readily ad-sorbed on the inner surfaces of the vacant cen-tral cavities. Molecules too large to passthrough the entry channels are excluded, giv-ing rise to the well-known “molecular sieving”property of most crystalline zeolites (figure 4).

Table 1.— Representative Formulae and Selected Physical Properties of Important Zeolites

Void Channel Thermal Ion-exchangeZeolite Representative unit-cell formulaa volume a dimensions a stability capacity b

AnalcimeChabaziteClinoptiloliteErioniteFaujasiteFerrierite

Heulandite

LaumontiteMordenite

Phillipsite

Linde ALinde X

18%4739?3547

39

28

31

4750

2.6 A3.7 X 4.23.9 x 5.43.6 X 5.27.44.3 x 5.53.4 X 4.84.0 x 5.54.4 X 7.24.1 x 4.74.6 X 6 . 32.9 X 5.76.7 X 7 . 04.2 X 4 . 42.8 X 4.83.34.27.4

HighHighHighHighHighHigh

Low

LowHigh

Low

HighHigh

4.54 meq/g3.812.543.123.392.33

2.91

4.252.29

3.87

5.484,73

aTaken mainly from Breck, 1974, Meier and Olson, 1971 Void volume is determined from water contentbCalculated from unit-cell formula

130

Figure 1. —Simple Polyhedron of Silicate and Aluminate Tetrahedra

a b

(a) Ball and peg model of truncated cube-octahedron. (b) Line drawing of truncated cube-octahedron,lines connect centers of tetrahedral

Figure 2.—Arrangements of Simple Polyhedra toEnclose-Large Central Cavities

a b

(a) Truncated cube-octahedra connected by double four-rings of oxy-gen in structure of synthetic zeolite A. (b) Truncated cube-octahedraconnected by double six-rings of oxygens in structure of faujasite.

The internal surface area available for adsorp-tion ranges up to several hundred square me-ters per gram, and some zeolites are capableof adsorbing up to about 30 weight percent ofa gas, based on the dry weight of the zeolite.

In addition to their ability to separate gasmolecules on the basis of size and shape, theunusual charge distribution within a dehy-drated void volume allows many species withpermanent dipole moments to be adsorbed

with a selectivity unlike that of almost all othersorbents. Thus, polar molecules such as water,sulfur dioxide, hydrogen sulfide, and carbondioxide are preferential] y adsorbed by certainzeolites over nonpolar molecules, such as meth-ane, and adsorption p recesses have been de-veloped using natural zeolites by which carbondioxide and other contaminants can be re-moved from impure natural gas or methanestreams, allowing the gas to be upgraded tohigh-Btu products. In addition, the small, butfinite, quadripole moment of nitrogen allowsit to be adsorbed selectively from air by a de-hydrated zeolite, producing oxygen-enrichedstreams at relatively low cost at room temper-ature. Both of the above processes may find ap-plication in agricultural technology.

Dehydration-rehydration properties: Becauseof the uniform nature of the pores of structuralcages, crystalline zeolites have fairly narrowpore-size distributions, in contrast to othercommercial absorbents, such as activated alu-mina, carbon, and silica gel. Adsorption on zeo-lites is therefore characterized by Langmuir-typeisotherms, as shown in figure 5. Here, percentof adsorption capacity is plotted against par-tial pressure of the adsorbate gas. Note that al-most all of the zeolite’s adsorption capacity for

Figure 3.—Solid Sphere Models of Synthetic Zeolite and Chabazite

a b

(a) Solid-sphere model of the crystal structure of synthetic zeolite A (b) Solid-sphere model of the crystal structure of chabazite

Figure 4.—Stylized Illustration of the Entry of Straight.Chain Hydrocarbons and Blockage of Branch-Chain

Hydrocarbons at Channel Apertures

Figure 5.—Langmuir-Type Isotherm for Adsorption onCrystalline Zeolites Illustrating Almost Complete

Saturation at Low Partial Pressures of the Adsorbate

a particular gas (including water) is obtainedat very low partial pressures, meaning that al-though their total adsorption capacity may besomewhat less than those of other absorbents,(e.g., silica gel), zeolites are extremely efficientad sorbents even at low partial pressures. Thisproperty has been used in the zeolitic adsorp-tion of traces of water from Freon gas lines ofordinary refrigerators that might otherwisefreeze and clog pumps and valves. The extremenonlinearity of the water adsorption isothermsof zeolites has been exploited recently in thedeveloprnent of solar-energy refrigerators (81),

lon-exchange properties: The exchangeablecations of a zeolite are also only loosely bondedto the tetrahedral framework and can be re-moved or exchanged from the framework

structure easily by washing with a strong so-lution of another element. As such, crystallinezeolites are some of the most effective ion ex-changers known to man, with capacities of 3to 4 meq per gram being common. This com-

132

pres with the 0.8 to 1.0 meq per gram cation-exchange capacity of bentonite, the only othersignificant ion-exchanger found in nature,

Cation-exchange capacity is basically a func-t ion of the degree of substitution of aluminumfor silicon in the zeolite framework: the greaterthe substitution, the greater the charge defi-ciency of the structure, and the greater thenumber of alkali or alkaline earth atoms re-quired for electrical neutrality. In practice,however, the cation-exchange capacity is de-pendent on a number of other factors as well,In certain species, cations can be trapped instructural positions that are relatively inacces-sible, thereby reducing the effective exchangecapacity of that species for that ion, Also, ca-tion sieving may take place if the size of theexchanging cat ion is too large to pass throughthe entry channels into the central cavities ofthe structure.

Unlike most noncrystalline ion exchangers,such as organic resins or inorganic alumino-silicate gels (mislabeled in the trade as “zeo-lites”), the framework of a crystalline zeolitedictates its selectivity toward competing ions.The hydration spheres of high-charge, small-size ions (e. g., sodium, calcium, magnesium)prevent their close approach in the cages to theseat of charge of the framework; therefore ionsof low charge and large size (e. g., lead, barium,potassium), that normally do not have hydra-tion spheres are more tightly held and selec-tively taken up from solution than are otherions, The small amount of aluminum in thecomposition of clinoptilolite, for example, re-sults in a relatively low cation-exchange capac-ity (about 2.3 meq/g); however, its cation selec-tivity is:

Cesium > Rubidium > Potassium > Ammonium >Barium > Strontium > Sodium

Calcium > Iron > Aluminum >Magnesium > Lithium (3).

Synthetic zeolite A, on the other hand, is moreselective for calcium than for sodium, and thus,acts as a water softener in laundry detergentswhere it picks up calcium from the wash waterand releases sodium (75).

Cation exchange between a zeolite (Z) anda solution (S) is usually shown by means of anexchange isotherm that plots the fraction of theexchanging ion (X) in the zeolite phase againstthat in the solution (figure 6). If a given cationshows no preference of either the solution orthe zeolite, the exchange isotherm would be thestraight line “a” at 450. If the zeolite is moder-ately or very selective for the cation in solution,curve b and c would result, respectively. If thezeolite is rejective of a particular cation, curved would result. Such is the selectivity of clin-optilolite for cesium or ammonium, for exam-ple. Clinoptilolite will take up these ions readilyfrom solutions even in the presence of highconcentrations of competing ions, a facilitythat was exploited by Ames (4) and Mercer, etal. (50), in their development of an ion-ex-change process to remove ammoniacal nitro-gen from sewage effluent.

Figure 6.—Types of Ion-Exchange Isotherms for the

133

APPLICATIONS

Fertilizer and Soil Amendments

Based on their high ion-exchange capacityand water retentivity, natural zeolites havebeen used extensively in Japan as amendmentsfor sandy soils, and small tonnages have beenexported to Taiwan for this purpose (52,31),The pronounced selectivity of clinoptilolite forlarge cations, such as ammonium and potas-sium, has also been exploited in the prepara-tion of chemical fertilizers that improve thenutrient-retention ability of the soils by promot-ing a slower release of these elements for up-take by plants, In rice fields, where nitrogenefficiencies of less than 50 percent are not un-common, Minato (52) reported a 63 percent im-provement in the amount of available nitrogenin a highly permeable paddy soil 4 weeks af-ter about 40 tons/acre zeolite had been addedalong with standard fertilizer (figure 7), Turner(84), on the other hand, noted little change inthe vitrification of added ammonia when clin-

Figure 7.—Change of Soil Nitrogen of Paddy SoilWith Time

Vertical water seepage in soil = 1.35 cm/day (Yamagata PrefectureBoard of Agriculture and Forestry, 1966; reported in Minato, 1968.)

IN AGRONOMY

optilolite was mixed with a Texas clay soil, al-though the overall ion-exchange capacity of thesoil was increased. He attributed these conflict-ing results to the fact that the Japanese soilscontained much less clay, thereby accountingfor their inherent low ion-exchange capacityand fast-draining properties. The addition ofzeolite, therefore, resulted in a marked im-provement in the soil’s ammonium retentivity.These conclusions support those of Hsu, et al.(31), who found an increase in the effect of zeo-lite additions to soil when the clay content ofthe soil decreased. Although additions of bothmontmorillonite and mordenite increase thecation-exchange capacity of upland soils, thegreater stability of the zeolite to weathering al-lowed this increase to be retained for a muchlonger period of time than in the clay-enrichedsoils (22),

Using clinoptilolite tuff as a soil conditioner,the Agricultural Improvement Section of theYamagata Prefectural Government, Japan, re-ported significant increases in the yields ofwheat (13 to 15 percent), eggplant (19 to 55 per-cent), apples (13 to 38 percent), and carrots (63percent) when from 4 to 8 tons of zeolite wasadded per acre (83). Small, but significant im-provements in the dry-weight yields of sor-ghum in greenhouse experiments using a sandyloam were noted when 0.5 to 3.0 tons of clinop-tilolite per acre was added along with normalfertilizer (47). However, little improvement wasfound when raising corn under similar condi-tions. Hershey, et al. (29), showed that clinop-tilolite added to a potting medium for chrysan-themums did not behave like a soluble Ksource, but was very similar to a slow-releasefertilizer, The same fresh-weight yield wasachieved with a one-time addition of clinop-tilolite as with a daily irrigation of Hoagland’ssolution, containing 238 ppm K, for threemonths (total of 7 g potassium added), with noapparent detrimental effect on the plants (fig-ure 8).

Experiments by Great Western Sugar Co. inLongmont, CO, using clinoptilolite as a soilamendment, resulted in a significant increase

134

Figure 8.— Yield of Chrysanthemums as a Functionof Potassium Level Supplied by One-Time Additions

of Clinoptilolite

tops also increased with the zeolite treatmentcompared with an ammonium sulfate control(table 2). These authors also found that natu-ral clinoptilolite added to soil in conjunctionwith urea reduced the growth suppression thatnormally occurs when urea is added alone (ta-ble 3). The presence of zeolites also resultedin less NO3-N being leached from the soil (fig-ure 9).

Both zeolite treatments apparently made con-siderably more ammonium available to theplants, especially when clay-poor soils wereemployed. The authors suggested that ammo-nium-exchanged clinoptilolite acted as a slow-release fertilizer, whereas, natural clinoptilo-lite acted as a trap for ammonium that was pro-duced by the decomposing urea, and therebyprevented both ammonium and nitrate toxic-ity by disrupting the bacterial vitrificationprocess. The ammonium selectivity of zeoliteswas exploited by Varro (85) in the formulationof a fertilizer consisting of a 1:1 mixture of sew-age sludge and zeolite, wherein the zeolite ap-parently controls the release of nitrogen fromthe organic components of the sludge.

Coupled with its valuable ion-exchange prop-erties which allow a controlled release of mi-cronutrients, such as iron, zinc, copper, man-

Table 2.—Growth Response of Radishes to Ammonium-Exchange Clinoptilolitea

130/0 clay soilb 6°/0 clay soilc

Parameter N H4-Clinoptilolite (NH4)2S 04 N H4-Clinoptilolite (NH4)2S 04

Leaf area (cm2/plant) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 187 187 150Plant weight (dry weight) (g). . . . . . . . . . . . . . . . . . . . . . . . . . . 1.84 1.12 1.40 1.1Root weight (g) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.5 8.5 11.6 7.6N uptake (mg N/plant top) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57.2 35.9 42.6 38.9aLewis, et al., 1980.bPlants sampled 36 days after planting.cLeached five times; plants sampled 34 days after planting.

Table 3.—Growth Response of Radishes to Natural Clinoptilolite Plus Ureaa

13% clay soilb 6°/0 clay soilc

Parameter Zeolite + Urea Urea Zeolite + Urea Urea

Leaf area (cm2/plant) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210 187 208 116Plant weight (dry weight) (g) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.59 1.23 1.38 0.71Root weight (g) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.8 12.4 6.3N uptake (mg N/plant top) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45.5 38.6 44.4 18.9aLewis, et al., 1980.bPlants sampled 36 days after planting.cLeached five times; plants sampled 34 days after planting.

Figure 9. —Cumulative Leachate N03-N for BandedNH4-Exchanged Clinoptilolite and Banded

Ammonium Sulfate (Lewis, et al., 1980)

135

issued to Aleshin, et a], (2), for grouting com-pound containing 3 to 5 percent clinoptiloliteto control herbicide percolation from irrigationcanals to ground waters.

Heavy Metal Traps

Not only do the ion-exchange properties ofcertain zeolites allow them to be used as car-riers of nutrient elements in fertilizers, they canbe exploited to trap undesirable metals and pre-vent their uptake into the food chain. Pulver-ized zeolites effectively reduced the transfer offertilizer-added heavy metals, such as copper,cadmium, lead, and zinc, from soils to plants(18). The selectivity of clinoptilolite for such

ganese, and cobalt, the ability of clinoptiloliteto absorb excess moisture makes it an attrac-tive addition to chemical fertilizers to preventcaking and hardening during storage and to an-imal feedstuffs to inhibit the development ofmold (82). Spiridonova, et a]. (78), found that0.5 percent clinoptilolite added to ammoniumnitrate fertilizer decreased caking by 68 percent.

pesticides, Fungicides, Herbicides

Similar to their synthetic counterparts, thehigh adsorption capacities in the dehydratedstate and the high ion-exchange capacities ofmany natural zeolites make them effective car-riers of herbicides, fungicides, and pesticides.Clinoptilolite can be an excellent substrate forbenzyl phosphorothioate to control stem blast-ing in rice (88). Using natural zeolites as a base,Hayashizaki and Tsuneji (26) found that clinop-tilolite is more than twice as effective as a car-rier of the herbicide benthiocarb in eliminat-ing weeds in paddy fields as other commercialproducts. Torii (82) reported that more than 100tons of zeolite were used in Japan in 1973 ascarriers in agriculture. A Russian patent was

ers (e. g., 74,19,1 1,76).

In view of the attempts being made by sani-tary and agricultural engineers to add munici-pal and industrial sewage sludge to farm andforest soils, natural zeolites may play a majorrole in this area also. The nutrient content ofsuch sludges is desirable, but the heavy metalspresent may accumulate to the point wherethey become toxic to plant life or to the ani-mals or human beings that may eventual] y eatthese plants. Cohen (12) reported median val-ues of 31 ppm cadmium, 1,230 ppm copper,830 ppm lead, and 2,780 ppm zinc for sludgesproduced in typical U.S. treatment plants. Zeo-lite additives to extract heavy metals may bea key to the safe use of sludge as fertilizer andhelp extend the life of sludge-disposal sites orof land subjected to the spray-irrigation proc-esses now being developed for the disposal ofchlorinated sewage. Similarly, Nishita andHaug (64) showed that the addition of clinop-tilolite to soils contaminated with radioactivestrontium (Sr90) resulted in a marked decreasein the uptake of strontium by plants, an obser-vation having enormous import in potentialtreatment of radioactive fallout that contami-nates soils in several pacific atolls where nu-clear testing has been carried out,

136

APPLICATIONS IN ANIMAL HUSBANDRY

Animal Nutrition

Based on the successful use of montmorillo-nite clay in slowing down the passage of nu-triants in the digestive system of chickens andthe resultant improvement in caloric effieiency(73), experiments have been carried out in Ja-pan since 1965 on the application of naturalzeo1ites as dietary supplements for severaltypes of domestic animals. Because much ofthis work was superficial or not statistically sig-nificant, it has been repeated and enlargedupon in recent years by researchers in theUnited States and several other countries seek-ing agricultural applications for zeolites.

Poultry

Using clinoptilolite from the Itaya r-nine,Yamagata Prefecture, and mondenite fromKarawago, Miyagi Prefecture, Onagi (67) foundthat Leghorn chickens required less food andwater and still gained as much weight in a 2-week trial as birds receiving a control diet.Feed efficiency values (FEV) l were markedlyhigher at all levels of zeolite substitution; feed-stuffs containing 10 percent zeolite gave riseto efficiencies more than 20 percent greaterthan those of normal rations (table 4). Adverseeffects on the health or vitality of the birds werenot noted, and the droppings of groups receiv-ing zeolite diets contained up to 25 percent lessmoisture than those of control groups, after a

1 Weight gain/feed intake, excluding zeolite,

12-day drying period, making them conSider-ably easier to hand1e.

Broiler chickens fed a diet of 5 percent c1i-noptilite from the Hector, CA, deposit gainedslight1y 1ess weight over a 2-month period thanbirds receiving a normal diet, but average FEVS

were noticeably higher (table 5) (6). Perhaps ofgreater significance is the fact that none of the48 test birds on the zeolite diet died during theexperiment, while 3 on the control diet and 2on the control diet supplemented with antibi-otics succumbed. In addition to an apparentfeed-efficiecy increase of 4 to 5 percent, theprescnce of zeolite in the diet appears to havehad a favorable effect on the mortality of thebirds.

Hayhurst and Willard (27) confirmed manyof Onagi’s observations and reported small in-creases in FEV for Leghorn roosters over a 40-day period, especially during the first 10 days.The birds were fed a diet containing 7.5 per-cent clinoptilolite crushed and mixed directlywith the normal rations. Feces were noticea-bly dryer and less odoriferous. Unfortunate\,only 17 birds were used in the study and ex-tensive statistical evaluation of the resultscould not be made.

Swine

Kondo and Wagai (39) evaluated the use ofzeolites in the diets of young and mature York-shire pigs in 60- and 79-day experiments, re-

Table 4.—Caloric Efficiencies of Zeolite Supplements in poultry Feedinga

Z e o l i t e c o n t e n t A v e r a g e A v e r a g e A v e r a g e A v e r a g e Feed efficiencyGroup no. of rations starting wt. (g) final wt. (g) weight gain (g) feed intakeb (g) ratio c

1 . . . . . . . . . . . . . . . . . . . . 10 percent Cpd 553.7 795.6 241.9 668 0.3622 . . . . . . . . . . . . . . . . . . . . 5 percent Cp 540.7 778 237.3 697 0.3403 . . . . . . . . . . . . . . . . . . . . 3 percent Cp 556.7 796 239.3 748 0.3204 . . . . . . . . . . . . . . . . . . . . 10 percent Mo 532.3 757.3 225.0 634 0.3555 . . . . . . . . . . . . . . . . . . . . 5 percent Mo 552.3 814.6 262.3 775 0.3386 . . . . . . . . . . . . . . . . . . . . 3 percent Mo 534.5 791.3 256.8 769 0.3347 . . . . . . . . . . . . . . . . . . . . Control 556.5 789.3 232.8 782 0.298aOnagi (1966) Tests carried out on 48-day-old Leghorns over a 14-day period, 30 birds/group. Normal rations consisted of 16.5 Percent crude Protein and 66 Percent

digestible nutrientsbExcluding zeolite.cFeed efficiency - weight gain/feed intake (excluding zeolite).d Cp = clinoptilolite, Mo - mordenite.

137

Table 5.—Apparent Caloric Efficiency of Zeolite in Chicken Rationsa

Average AverageTreatment of weight (g) consumption (g)—

4-week datad

Control diet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 730 1175Control diet + antibiotics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 708 1116Control diet with 5 percent clinoptilolite . . . . . . . . . . . . . . . . . . . . . . . . 703 1070

8-week dataf

Control diet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1869 3978Control diet + antibiotics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1882 3869Control diet with 6 percent clinoptilolite . . . . . . . . . . . . . . . . . . . . . . . . 1783 3647

Average Survivors ofF.E.V.C 48 birds

0.622 460.634 470.657 48

0.470 450.486 460.489 48

dStarter rations (O to 4 weeks)aAdapted from data of Arscott (1975)e55 ppm Zinc bacitracinbFeed consumed, excluding zeolite

CFeed efficiency value = weight/feed consumed (excluding zeolite) fFinisher rations (4 to 9 weeks)

spectively, and found that the weight gain ofanimals of both ages receiving diets contain-ing 5 percent clinoptilolite was from 25 to 2 9percent greater than that of animals receivingnormal diets (table 6). Feed supplemented withzeolites gave rise to feed efficiencies about 35percent greater than those of normal rationswhen fed to young pigs, but only about 6 per-cent greater when given to older animals. Inaddition, the particle size of the feces of thecontrol group was noticeably coarser than thatof the experiment group, suggesting that thedigestive process was more thorough whenzeolites were added to the diet. The feces ofanimals in the control group were also richerin all forms of nitrogen than zeolite-fed ani-mals, indicating that the zeolites contributedtoward a more efficient conversion of feedstuffnitrogen to animal protein.

The digestibility of crude protein and nitro-gen-free extracts tended to be improved as zeo-lite was substituted for wheat bran in swinediets at levels from 1 to 6 percent over a 12-week period (24,26). Anai, et al. (5), reportedsimilar results using 5 percent zeolite for 8 pigs

over a 12-week period and realized a 4-percentdecrease in the cost of producing body weight.They also noted a decrease in malodor andmoisture content of the excrement, Toxic orother adverse effects were not noted for anyof the test animals described. On the contrary,the presence of zeolites in swine rations ap-pears to contribute measurably to the well-being of the animals. Tests carried out on 4,000head of swine in Japan showed that the deathrate and incidence of disease among animalsfed a diet containing 6 percent clinoptilolitewas markedly lower than for control animalsover a 12-month period (83). As shown in ta-ble 7, the decrease in the number of cases ofgastric ulcers, pneumonia, heart dilation, andin the overall mortality is remarkable, The sav-ings in medicine alone amounted to about 75cents per animal, to say nothing of the in-creased value of a larger number of healthypigs.

In one test, the addition of zeolite to the dietof piglets severely afflicted with scours markedlyreversed the progress of this disease within afew days (53). Four underdeveloped Laundry

Table 6.—Caloric Efficiency of Zeolite Supplements in Swine Feeding a

Age of pigs Average weight

Start Finish Start Finish Average Average b Average c Zeolite(days) (kg) (kg) wt. gain (kg) feed intake (kg) F.E.V. improvement

Experimental d 60 120 15.43 44.43 29.00 85.0 0.341Control d 60 120 14.85 35.78 22.93 90.6 0.253 35 percentExperimentale 99 178 30.73 85.30 54.57 167.6 0.326Control e 99 178 31.20 73.50 42.30 136.2 0.308 6 percentaKOndo and Wagai (1968) Tests carried out using 5 percent clinoptilolite in rations of experimental groupsbExcluded zeolitecFeed efficiency value - weight gain/feed intake‘Eight Yorkshire pigseTwenty Yorkshire Pigs

138

Table 7.—Effect of Zeolite Diets on Health of Swinea

Zeolite content Sickness causes Heart Mortality MedicinePeriod of rations Gastric ulcer Pneumonia dilatation rate (percent) cost/head

2/72 to 1/73 . . . . . . . . . ........0 77 128 6 4.0 $2.502/73 to 1/74 . . . . . . . . . ........6 percent clinoptilolite 22 51 4 2.6 $1.75aTest carried out on 4,000 swine at Keai Farm, Morioka, Iwate Prefecture, Japan (Torii, 1974)

pigs were fed a diet containing 30 percent zeo-lite for the first 15 days and 10 percent zeolitefor the remaining part of a month-long exper-iment. The severity of the disease decreasedalmost at once, and feces of all pigs were hardand normal after only 7 days. Although the pigsconsumed an average of 1.75 kg of zeolite perhead per day, no ill effects were noted, andonce they had recovered from diarrhetic ail-ments, the pigs regained healthy appetites andbecame vital. A recent Japanese patent disclo-sure claimed a method of preventing and treat-ing gastric ulcer in swine by the addition ofzeolite to their diets (49); supportive data, how-ever, were not reported.

Apparently the vitalizing effect of a zeolitediet can be transferred from mother to off-spring. Experiments at the Ichikawa LivestockExperiment Station, where 400 g of clinoptilo-lite was fed each day to pregnant sows and con-tinued through the 35-day weaning period oftheir offspring, showed substantial increase inthe growth rate of the young pigs, As shownin table 8, test animals weighed from 65 to 85percent more than control-group animals at theend of the weaning period (9). Young pigswhose dams received the zeolite diet also suf-fered almost no attacks of diarrhea, while thosein control groups were severely afflicted withscours, greatly inhibiting their normal growth.The addition of 5 percent zeolite to the rationsof pregnant sows 20 to 90 days after mating

gave rise to improved FEVs and increased lit-ter weight at parturition (46), The earlier thezeolite was added, the greater was the appar-ent effect.

Similar studies were conducted at OregonState University with young swine using ra-tions containing 5 percent clinoptilolite (16).Although lesser increases in growth rates werefound than in the Japanese studies, the inci-dence of scours was significantly reduced foranimals receiving the zeolite diet. Currently,heavy doses of prophylactic antibiotics areused to control such intestinal diseases, which,left unchecked, result in high mortality amongyoung swine after they are weaned. Federalregulations are becoming increasingly strin-gent in this area, and if antibiotics are prohib-ited, other means must be found to control suchdiseases. Natural zeolites may be the answer.

In a preliminary study involving 16 earlyweaned pigs over a 19-day period, animals onan antibiotic-free diet containing 10 percentclinoptilolite gained about 5 percent moreweight per pound of feed than those on a con-trol diet without antibiotics and about 4 per-cent more than those on an antibiotic-enricheddiet (table 9) (70). The small number of pigsused, however, limits the significance of thesefindings. In another study, a 30 percent im-provement in FEVs occurred for 35 young pigson a molasses-based diet when 7.5 percent

Table 8.—Effect of Prenatal Zeolite Diet on Newborn Pigsa

Average weight (kg)Species No. of pigs Group Newborn 21-days 35-days Weight gain improvementYorkshire 6 Experimental 1.25 4.3 7.83Yorkshire 10 Control 1.10 4.2 4.81 63 percentLaundry 6 Experimental 1.20 4.7 8.68Laundry 10 Control 1.10 4.0 4.67 96 percentaTest carried out at lchikawa Livestock Experiment station, Japan Four hundred grams of clinoptilolite given to sows n experimental group per day and continued

to end of weaning period (Buto and Takenashi, 1967)bweight-gain of experimental animals - weight-gain of control animals x 100.

139

Table 9.—Effect of Zeolite Supplement in the Diets of Early Weaned Pigsa

Basal dietb Zeolite dietc Antibiotic dietd

Number of pigs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4 4Average daily weight gain (g). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 245 304Feed efficiency value (FEV)e (weight gain/feed intake) . . . . . . . . . . . . . . 0.432 0.455 0.437aPond and Mumpton (1978b62% ground yellow corn 10% cerelose, 23% soybean meal, 0.5% salt, 0.5% Hopro R vitamin supplement, 1.5% ground limestone, 2.5% dicalcium phosphatecBasal diet less 10% cerelose plus 10°/0 clinoptilolite, -200 mesh, Castle Creek, IdahodBasal diet plus 0.3% Aurofac 10 antibiotic

eExcluding zeolite

clinoptilolite was substituted in the diet dur-ing the 35 to 65 kg growth period (table 10) (10).Feces of the zeolite-fed animals were also lessliquid than those on a control diet.

The addition of zeolites had little effect onthe FEVs in the 65 to 100 kg growth range.Heeney (28) supplemented normal corn-soy ra-tions of 36 pigs with 2,5 and 5 percent clinop-tilolite in a 120-day experiment (table 11). Hefound little overall difference in the FEVs; how-ever, for the first 30 days after weaning, FEVsof 0.455 and 0.424 were obtained for 2.5 and5.0 percent zeolite, respectively, comparedwith a value of 0.382 for the control animals,an increase of about 15 percent due to the pres-ence of zeolites in the diet. Little improvementwas noted between 30 and 120 days of thetreatment.

Ruminants

In an attempt to reduce the toxic effects ofhigh NH, + content of ruminal fluids whennonprotein nitrogen (NPN) compounds, such

as urea and diuret, are added to the diets of cat-tle, sheep, and goats, researchers introducedboth natural and synthetic zeolites into the ru-men of test animals (87). Ammonium ionsformed by the enzyme decomposition of NPNwere immediately ion exchanged into the zeo-lite structure and held there for several hoursuntil released by the regenerative action ofNa + entering the rumen in saliva during theafter-feeding fermentation period. Both in vivoand in vitro data showed that up to 15 percentof the NH 4 + in the rumen could be taken upby the zeolite. Thus, the gradual release ofNH4 + allowed rumen micro-organisms to syn-thesize cellular protein continuously for easyassimilation into the animals’ digestive sys-tems. The zeolite’s ability to act as a reservoirfor NH4 + “. . . permits the addition of supple-mental nitrogen to the animal feed while pro-tecting the animal against the production oftoxic levels of ammonia” in the rumen (87).

Clinoptilolite added to the feed of youngcalves improved their growth rate by stimulat-ing appetite and decreased the incidence of di-

Table 10.—Effect of Zeolite Supplement in Molasses-Based Diets of Young Pigsa

Zeolite level (%)

o 2.5 5 7.5 10

35-65 kg growth stage

Daily gain ( ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 621 694 700 704 659Daily intake (g). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2900 3110 3090 2970 3040Daily feed intakec (g) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2900 3030 2940 2750 2740Feed efficiency value (FEV)d (weight gain/feed intake) . ............0.214 0.229 0.238 0.256 0.241

65-100 kg growth stages

Daily gain ( ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541 582 526 562 535Daily intake (g). ., ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3550 3900 4260 4430 4140Daily feed intakec (g) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3550 3800 4050 4100 3730Feed efficiency value (FEV)d (weight gain/feed intake) . ............0.152 0.153 0.130 0.137 0.143aCastro and Elias (1978)blncluding zeoliteClntake less zeolite‘Excluding zeolite.

140

Table 11 .—Effect of Clinoptilolite Supplemental in the Diet of Swinea

Control

Average initial weight (lb) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.6----

30-days:Average weight (lb)..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61.0Average daily weight gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.09Feed/pound of gain (lb)b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.62Feed efficiency valuec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.382

60-days:Average weight (lb) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105.7Average daily weight gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.59Feed/pound of gain (lb)b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.80Feed efficiency valuec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.357

90-days:Average weight (lb) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.7Average daily weight gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.72Feed/pound of gain (lb)b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.33Feed efficiency valuec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.300

120-days:Average weight (lb) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188.2Average daily weight gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.56Feed/pound of gain (lb)b. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.94Feed efficiency valuec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.254

OverallAverage daily weight gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.49Feed/pound of gain (lb)b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.42

2.50/oClinoptilolite

31.7

62.21.122.200,455

107.31.613.050.328

149.61.513.430.292

177.81.285,630.178

1.403.45

50/0Clinoptilolite-.

31.7

62.51.172.360.424

106.21,523.090.324

150.01,573.670.272

176.41.274.300.233

1.373.34

Feed efficiency-valuec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.292 0.290 0.299aFrom Heeney (1977), 6 pigs in each treatment. Control diet - 76.9% ground corn, 20% soybean 011 meal, 1.5% dicalcium phosphate, 0.5% CaCo3, 0.5% salt, 0.1%

trace mineral 0.25% vitamin premix, 025°/0 ASP250 antibiotic Zeolite diets contained 25 and 5°A replacement of corn.bExcluding zeoliteCWeight gain/feed Intake, excluding zeolite

arrhea and soft feces (38). Five percent zeolitewas added to the normal grass and hay dietsof lo-and 184-day-old heifer calves over a 180-day period. The animals on the zeolite-supple-mented diets gained approximately 20 percentmore weight than those in control groups, andalthough the test calves consumed more feed,the feeding costs per kilogram of weight gainedwere significantly less than for control animals.No deleterious effects were noted, and the fe-ces of the test animals contained slightly lesswater and fewer particles of undigested solids.The incidence of diarrhea and soft-feces wasmarkedly less in zeolite-fed calves than in con-trol animals (table 12)

Watanabe, et al. (86) raised six young bul-locks for 329 days on a diet containing 2 per-cent clinoptilolite, along with 72 percent digest-ible nutrients and 11 percent crude protein.Although little difference in the final weightsof test and control animals was noted, teststeers showed slightly larger body dimensionsand reportedly dressed out to give slightly high-

er quality meat. These differences were re-flected in the overall higher prices obtained forthe test animals and a 20 percent greater profit.In addition, diarrhea and other intestinal ail-ments were noticeably less prevalent in the ani-mals on the zeolitc diet, and the excrementfrom these animals was significantly less odor-iferous, again testifying to the retentivity ofclinoptilolite for ammonia. It is unfortunatethat a higher level of zeolite was not used inthese experiments; earlier studies in the UnitedStates showed that as much as 40 percent claycould be added to animal rations without ad-verse effects (68),

One study found increased protein digestionwhen 5 percent powdered clinoptilolite wasadded to a high-volubility protein diet of 18 Hol-stein steers and cows over a 118-day period;however, statistically significant weight in-creases were not noted, The addition of 2 per-cent zeolite to the rations of cows was effec-tive in preventing diarrhea and in increasingmilk product ion (20). These effects were appar-

141— —— ——.—

Table 12.–Occurrence of Diarrhea and Soft-Feces Among Calves on Diets Supplemented With5% Cl inopt i lo l i tea

—Incidence of diarrhea Incidence of soft-feces

Grass-fed Hay-fed Control Grass-fed H a y - f e d - C o n t r o l

30 . . . . . . . . . . . . . . . . . . . . . . . . . . 0 036-60 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 161-90 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . O 091-120 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0121-150 . . . . . . . . . . . . . . . . . . . . . . . . . . . O 0151-184. . . . . . . . . . . . . . . . . . . . . . . . . . . 0 0

4 0 0 42 9 4 132 1 1 131 2 0 134 4 0 80 0 0 0

Total 1 1aData summarized from Kondo et al (1969)

Excrement Treatment

In the Unitcd States, livestock productioncreates more than 1 billion metric tons of solidwastc and nearly 400 million tons of liquidwaste each year (43). Accumulations of suchmagnitude pose serious problems to the healthof man and beast alike and can pollute nearbystreams and rivers. In addition, the largeamount of undigested protein remaining in theexcrement represents a valuable resource thatfor the most part is being wasted because ofour growing dependence on chemical fertil-izers. The physical and chemical properties ofmany natural zeolites lend themselves to a widevariety of applications in the treatment of ani-mal wastes, including the:

c reduction of malodor and associated pol-lution,

c creation of healthier environments for con-fined livestock,

Q control of the viscosity and nutrient reten-tivity of the manure, and

c purification of methane gas produced by an-aerobic digestion of the excrement.

Malodor and Moisture Control

The semifluid droppings in large poultryhouses commonly emit a stench that is discom-forting to farm workers and to the chickensthemselves. The noxious fumes of ammoniaand hydrogen sulfide contribute to decreased

13 16 5 51—

reSistance to respiratory diseases and result insmaller and less healthy birds (15,35). In manyareas of Japan clinoptilolite is now mixed withthe droppings directly or packed in boxes sus-pended from ceilings to remove ammonia andthereby improve the general atmosphere inchicken houses (82). The net result is reportedto be an overall increase in egg production andhealthier birds.

One study used a zeolite-packed air scrub-ber to improve poultry-house environments(36). By passing ammonia-laden air over aseries of trays containing crushed clinoptilo-lite, 15 to 45 percent of the NH3-N was removedeven though the contact time was less than onesecond. There was an associated reduction inodor intensity. The use of such a scrubbercould improve the quality of the air in poultryhouses without the loss of heat that accompa-nies normal ventilation. The ammonium-loadedzeolite could then be used as a valuable soilamendment on disposal.

Water content, maggot population, and am-monia production can be all minimized whenchicken droppings are mixed with one-thirdzeolite (table 13). Similar results can be ob-tained if powdered zeolite is added directly tothe rations of the birds, all without affectingthe vitality or growth rate of the chickens (67).Apparently, gaseous ammonia reacts with thehydrous zeolite to form ammonium ions thatare selectively ion-exchanged and held in thezeolite structure. These experiments suggestthat the addition of zeolites to poultry wastescould reduce labor costs associated with air-drying or the high energy costs of thermal treat-

142

Table 13.—Effect of Zeolite Additions toChicken Droppings

Property 2.1 3:1 5:1 10,1 Control

Moisture content (%) 123 131 134 157 185Maggot content (counts per

unit area) 38 101 172 387 573Ammonia generation (relative

quantities) 315 370 245 500 450aOnagi (1965) Clinoptilolite was spread on droppings of Leghorn chickens

every third day for a 15-day period The total amount of droppings iS the samein all tests, Including the control

ment, whilc at the same time retain the valu-able fertilizer components and meet ecologi-cal standards.

In swine raising, pigs fed a diet containing10 percent cinoptilolite had feces richer in allforms of nitrogen after drying than those fromcontrol groups (vide supra) (39). As a result ofthis study and of other investigations, about 25tons of clinoptilolite per month is spread onthe floors of a Sapporo swine-raising facilityto adsorb urine and other liquid wastes (82).The buildings were said to be dry, clean, andconsiderably less odoriferous. In Akita Prefec-ture, Japan, a zeolitic mudstone is used to treatoffensive odors and to reduce moisture contentof swine excrement (30). The dried manure isthen sold as an inexpensive rice fertilizer.

An innovative application of zeolites in ex-crement treatment was patented and involvesthe addition of a natural zeolite and ferrous sul-fate to chicken droppings (37), The ferrous sul-fate inhibits zymosis and decomposition of thedroppings, and the zeolite stabilizes the hygro-scopic nature of this compound and capturesN H4 + produced in the manure. The mixtureis dried at 1200 to 1500 C and used as an odor-less, organic fertilizer, It is also used as a pro-tein-rich feedstuff for fish, fowl, and domes-tic animals.

Methane Purification

Although it is well known that anaerobic di-gestion of animal excrement and other organicwastes produces an impure methane-gas prod-uct, this source of energy has generally beenignored for anything except local or in-houseuse (32). One major drawback is the fact thatin addition to methane, copious quantities ofcarbon dioxide and sulfur compounds are also

produced during the digestion process, givingrise to low-Btu products that are extremely cor-rosive. Nevertheless, the process is still an at-tractive one, and Goeppner and Hasselmann(21) estimated that a billion cubic feet of 700Btu/ft 3 methane gas could be produced by treat-ing the 250,000 tons of manure produced eachday in the United States. The methane pro-duced by the anaerobic digestion of the organicwastes of a typical New York State dairy farmof 60 head may be equivalent to the farm’s en-tire fossil-fuel requirements (32).

A recent development of Reserve SyntheticFuels, Inc., using the adsorption properties ofnatural zeolites, suggests that this methane canbe economically upgraded to high-Btu prod-ucts. In 1975, this company opened a methane-recovery and purification plant to treat meth-ane gas produced by decaying organic matterin the Pales Verde landfill near Los Angeles,As shown schematically in figure 10, raw gascontaining about 50 percent methane and 40

Figure 10. —Methane-Purification System,Pales Verde Landfill

143

percent carbon dioxide is fed to two pretreat- feet of methane meeting pipeline specificationsment vessels to remove moisture, hydrogen sul- is produced each day and delivered to localfide, and mercaptans. The dry gas is then utility companies (65). Such a zeolite-adsorp-routed through three parallel columns packed tion process to upgrade impure methane pro-with pellets of dehydrated chabazite/erionite duced by the digestion of animal manure ap-and carbon dioxide is removed by adsorption pears to be technically feasible and awaitson the zeolite. Approximately 1 million cubic detailed economic and engineering evaluation.

AQUACULTURAL APPLICATIONS

In recent years, more and more fish productshave found their way to the dinner tables andfeeding troughs of every country, and the com-mercial breeding and raising of fish as a sourceof protein is becoming a major business in theUnited States and other countries, Many vari-eties of fish, however, are extremely sensitiveto minor fluctuations in such factors as watertemperature, pH, O2, H2S, and NH4+. Thechemical and biological environment of aqua-cultural systems must be maintained withinclose limits at all times. Processes based on theselective adsorption and ion-exchange proper-ties of several natural zeolites for oxygen aer-ation of hatchery and transport water and forthe removal of toxic nitrogen from tanks andbreeding ponds may contribute significantly toincreased product ion for human and animalconsumption.

Nitrogen Removal From Closedor Recirculation Systems

In closed or recirculating aquacultural sys-tems, NH4 + produced by the decompositionof excrement and unused food is one of theleading causes of disease and mortality in fish.I n oxygen-poor environments, even a fewparts-per-million NH4 + can lead to gill dam-age, hyperplasia, and substantial reduction ingrowth rates (42). Biological vitrification is acommon means of removing NH4 + from cul-ture waters; however, processes similar tothose used in municipal sewage-treatmentplants based on zeolite ion exchange have beenfound to be effective in controlling the nitro-gen content of hatchery waters (40). Zeolite ion

exchange might be a useful alternative to bio-filtration for NH4+-removal and have the ad-vantages of low cost and high tolerance tochanging temperatures and chemical condi-tions (33).

Unpublished tests conducted in 1973 at aworking hatchery near Newport, OR, indicatedthat 97 to 99 percent of the NH, + producedin a recirculating system was removed by clinop-tilolite ion-exchange columns (34). Trout alsoremained healthy during a 4-week trial whenzeolite ion exchange was used to regulate thenitrogen content of tank waters (69), Becker In-dustries of Newport, OR, in conjunction withthe U.S. Army Corps of Engineers, has devel-oped a single-unit purification facility forhatchery-water reuse. The system incorporatesa zeolite ion-exchange circuit for nitrogen re-moval and is designed to handle typical con-centrations and conditions encountered atmost of the 200 fish hatcheries operating in thePacific Northwest (34).

A similar ammonium-ion removal systemusing zeolite ion exchange for fish haulage ap-plications, where brain damage due to excessNH, + commonly results in sterility, stuntedgrowth, and high mortality has also been de-veloped (63). Three-way cartridges and filterscontaining granular clinoptilolite will also beavailable for home aquaria. The U.S. Fish andWildlife Service investigated zeolite ion-ex-change processes for the treatment of recircu-lating waters in tank trucks used to transportchannel catfish from Texas hatcheries to theColorado River in Arizona (48). If NH4+ canbe removed, the number of fish hauled in suchtrucks can be nearly tripled.

144

Aeration Oxygen Production

Oxygen-enriched air can be produced by theselective adsorption of nitrogen by activatedzeolites. A pressure-swing adsorption processcapable of producing up to 500 m 3 of 90 per-cent oxygen per hour was developed in Japanfor secondary steel smelting (80). Smaller gen-erators with outputs of as little as 15 liters of50 percent O2 per hour are also manufacturedand used to aerate fish breeding tanks and inthe transportation of live fish. Carp and gold-fish raised in such environments are said to belivelier and to have greater appetites (41), Inclosed tanks and stagnant ponds, oxygen aer-ation could markedly increase the number offish that could be raised per unit volume.

Oxygen produced by small, portable unitscontaining natural zeolite absorbents could beused to replenish free oxygen in small lakeswhere eutrophication endangers fish life. Fast,et al. (1 7), showed that the oxygen of hypolim-nion zones could be increased markedly by aer-ation using liquid O2 as a source. Haines (23)demonstrated side-stream pumping could im-prove the dissolved oxygen in the hypolimnionof a small lake in New York State.

Fish Nutrition

The high-protein rations used in commercialfish raising are quite expensive and their costhas been a limiting factor in the development

of large-scale aquacultural operations. Thephysiology of fish and poultry is remarkablysimilar, and if the results achieved with chick-ens can be duplicated with fish, the substitu-tion of small amounts of inexpensive zeolitesin normal fish food, with no adverse changein growth and perhaps a small increase in feedefficiency, could result in considerable savings.The quality of the water in recirculating sys-tems should also be improved by the use of zeo-lite-supplemented food, as should that of theeffluents. Leonard (44) reported preliminary re-sults of experiments where 2 percent clinop-tilolite was added to the normal 48 percent pro-tein food of 100 rainbow trout: after 64 days,a 10 percent improvement in the biomass in-crease was noted, with no apparent ill effectson the fish (table 14).

Table 14.—Effect of Clinoptilolite Additions to theDiet of Trouta

Control Test100% normal 98% normal feed

feedb 2% clinoptilolite

Average starting weight (g) 10.2 10.1Average 64-day weight 48,6 52.3Average weight gain 38.4 42,2Mortalitv. ... ~ ~ 4 3a100 rainbow trout.bStandard 48% protein fish food

OCCURRENCE AND AVAILABILITY OF NATURAL ZEOLITES

Geological Occurrence other hand, are ideally suited for simple, inex-

Since their discovery more than 200 years pensive, open-pit mining.

ago, natural zeolite minerals have been widely Most sedimentary zeolite deposits of eco-recognized by geologists as cavity and fracture nomic significance were formed from fine-fillings in almost every basaltic igneous rock. grained volcanic ash or other pyroclastic ma-Attractive crystals up to several centimeters in terial that was carried by the wind from ansize adorn the mineral museums of every coun- erupting volcano and deposited onto the landtry; however, such traprock occurrences are surface, into shallow freshwater or saline lakes,generally too low-grade and heterogeneous for or into the sea fairly close to the volcaniccommercial extraction. The flat-lying and near- source. Much of the land-deposited materially monomineralic sedimentary deposits, on the was quickly washed into lakes where it formed

beds of nearly pure ash. Successive eruptionsresulted in sequences of ash layers interstrati-fied with normal lake or marine Sediments,such as mudstoncs, silt stone, sandstones, andlimestones, as well as beds of diatomite, ben-tonite, and chert (figure 1 I).

The layers of volcanic ash (called volcanictuff) vary in thickness from less than a centi-metcr to several hundred meters and maystretch for 10 kilometers. Many of these bed-ded tuffs have been transformed almost com-pletely into well-formed, micrometer-size zeo-litc minerals. Zeolitically altered tuffs occur inrelatively young sedimentary rocks in diversegeological environments. Sedimentary zeolitedeposits of this kind have been classified intothe following types, with many gradations be-tween the types, Sheppard (77), Mumpton (54),and Munson and Sheppard (62):

1.

2.

3.4.

5.

6.

7.

145

deposits formed from volcanic materialsin hydrologically ‘ c l o s e d " s a l i n elake systems;deposits formed in hyrdrologially ‘open”fresh-water lake or ground watcr systems;deposits formed in marine environments;deposits formed by low-grade, burial meta-morphism;deposits formed by hydrothermal or hot-spring activity in bedded Sediments:deposits formed from volcanic materialsin alkaline soils;deposits formed without direct evidenceof volcanic precursors.

The most common zeolites in sedimentarydeposits are analclime, chabazite, c1inoptilolite,erionite, heulandite, laumontite, mordenite,phillipsite, and wairakite, with clinoptiloliteranking first in abundance. Except for heulan-

Figure 11.— Field Exposure of Zeolite Beds

146

dite, laumontite, and wairakite, “sedimentary”zeolites are alkalic and are commonly more si-licic than their igneous counterparts. Commer-cial interest is mainly in deposits of the firstfour types. Zeolite tuffs in saline-lake depositsare generally a few centimeters to a few metersthick and commonly contain nearly monomin-eralic zones of the larger pore zeolites, erioniteand chabazite that are relatively uncommon inother types of deposits. “Open-system” depos-its and marine tuffs deposited close to theirsource are generally characterized by clinop-tilolite and/or mordenite and may be severalhundred meters thick. Zeolitic tuffs are com-monly soft and lightweight, although somehard, siliceous deposits of clinoptilolite andmordenite are known. Many sedimentary zeo-lite beds contain as much as 95 percent of asingle zeolite species, while others consist oftwo or more zeolites with minor amounts ofcalcite, quartz, feldspar, montmorillonite clay,and unreacted volcanic glass.

Most zeolites in sedimentary rocks crystal-lized from volcanic ash by reaction of the amor-phous, aluminosilicate glass with pervadingpore waters derived either from saline lakes ordescending ground waters. Others originatedby the alteration of preexisting feldspars, feld-spathoids, biogenic silica, or poorly crystallineclay minerals. Although the exact mechanismof formation is still under investigation, zeo-lites in sedimentary rocks probably crystallizedas well-formed, micrometer-size crystals bymeans of a dissolution-reprecipitation mech-anism, with or without an intermediate gelstage (55) (figure 12).

The factors controlling whether a zeolite ora clay mineral formed or which of several zeo-lites formed from a given starting material arealso only poorly understood, although temper-ature, pressure, reaction time, and the concen-trations of the dissolved species, such as H+,silica, alumina, and alkali and alkaline earthelements, seem to be paramount in importance.Early formed species also tend to react furtherwith pore fluids of different composition, there-by yielding even more complex assemblages.

Figure 12.–Scanning Electron Micrograph ofClinoptilolite Laths With Minor Mordenite From a

Saline-Lake Deposit Tuff Near Hector, CA(from Mumpton and Ormsby, 1976)

Geographic Distribution

The distribution of zeolite deposits in vari-ous geographic regions of the world is gov-erned solely by the geology of those regions.Regions that have undergone past volcanic ac-tivity are likely to contain significant depositsof zeolite minerals. Although the zeolite phil-lipsite is known to have formed within the last10,000 years in a small saline-lake deposit atTeels Marsh, NV (79) by the alteration of vol-canic ash from the explosion of Mt. Mazuma(Crater Lake), and chabazite has been identi-fied in deposits on the walls of ancient Romanbaths in France, most potentially commercialdeposits of zeolites are of Tertiary or lowerPleistocene age (70,000 to 3 million years ago).Thus, any part of the Earth that was subjectedto volcanic activity during this period undoubt-edly contains extensive deposits of volcanicash, and if these ash deposits had an opportu-nity to react with percolating ground watersor alkaline pore waters from former salinelakes, beds of high-grade zeolites are apt toexist.

Although zeolites are now considered to besome of the most abundant and widespread au-

147

thigenic silicate minerals in sedimentary rocks,their existence as major constituents of alteredvolcanic tuffs is still not common knowledgeamong the geologists of many countries. Be-cause of their inherently fine crystal size, zeo-lites are not easily identified by ordinary micro-sscopic techniques and have often been missedby geologists and mineralogists studying theseformations. In general, zeolite identification re-quircs sophisticated X-ray diffraction and elec-tron microscopic equipment not available inmany geological laboratories; however, oncea particular soft, lightweight, clay-like rockfrom a particular area is identified in the lab-oratory as a zeolite rock, similar materials areeasy to locate in the field.

Table 15 lists the countries where zeoliteshave been reported from sedimentary rocks ofvolcanic origin and estimates the chances ofdiscovering additional deposits in these coun-tries. Sedimentary zeolites have been found onevery continent, although few have been re-ported from the Middle East, Latin America,or the East Indies, mainly because geologistsin these regions generally have been unawareof the widespread occurrence of zeolites inaltered volcanic tuffs. Wherever zeolites havebeen found, however, man has used the soft,lightweight tuffs for hundreds of years as eas-ily carved stone in a variety of structures rang-ing from walls and foundations of buildings tobarns and corrals to house livestock. Zeoliticblocks have been found in buildings associatedwith the Mayan pyramids at Monte Alban andMitla in southern Mexico (56) and are usedtoday in the construction of modern dwellingsin the Tokaj region of eastern Hungary. Zeo-lites are mined in only a dozen countries (ta-ble 16), but the potential is much greater.

The high probability of finding minable de-posits of zeolites in countries where they havenot yet been reported, but where there has beenconsiderable volcanic activity in the past, is il-lustrated by the discovery of major bodies ofsedimentary zeolites in Mexico and in centralTurkey in the early and late 1970s, respectively.Both countries show promise of becoming ma-jor suppliers of mineral raw materials in theyears to come, but, as with most developing na-

tions, they have only limited in-house geologi-cal expertise to service their blossoming min-eral industry.

During the late 1950s and 1960s the geologi-cal similarity}’ of the Western United States andnorthern Mexico led geologists to speculateabout the existence of zeolite deposits south ofthe border. It was not until 1972, however, thatthis author (56) discovered the first such de-posit in southern Oaxaca after visiting a largestone quarry during an unrelated project. Therock was being used as a local dimension stoneand closely resembled zeolitic tuffs that werebeing quarried in Japan. Subsequently, the Oax-acan rock was shown to consist of about 90percent clinoptilolite and mordenite. Shortlythereafter, several similar deposits were discov-ered in this part of Mexico and Mexican scien-tists quickly learned to recognize zeolitic tuffsin the field. One deposit was spotted in a roadcut while driving past it at 50 miles per hour,suggesting that many more await discoverywith only minimal exploration efforts. As a re-sult of these discoveries, at least three other de-posits of sedimentary zeolites have been foundin the northern part of the country by Mexi-can geologists who are now atune to the exis-tence of zeolites in volcanogenic environmentsand to their potential applications in industrialand agricultural technology.

Similar to Mexico, major parts of the centralAnatolian region of Turkey are covered bythick sequences of Tertiary volcanic rocks, but,with the exception of a few minor occurrencesof analcime in saline-lake environments, re-ports of zeolites in the volcanogenic sedimen-tary rocks of this country have been rare. Theprincipal reason for this is simply lack of ex-ploration combined with a lack of knowledgeabout the potential applications of such mate-rials in industry. Turkey’s few geologists havebeen more occupied with their chrome andborate resources, which are exported in largequantities to acquire badly needed currency.In 1977, however, several low-grade occur-rences of erionite and chabazite were uncov-ered in Turkey’s Cappadocia region, along witha major deposit of clinoptilolite (7). In 1979, asecond major deposit was discovered by the au-

148

Table 15.— Reported Occurrences of Sedimentary Zeolites

Zeolite . —Country species

Minable Minor Chances fordeposit occurrence finding deposit

Europe:BelgiumBulgaria

CzechoslovakiaDenmarkFinlandFranceGermany

Great Britain

Hungary

Italy

PolandRomaniaSoviet Union

Spain

Switzerland

Turkey

Yugoslavia

North America:Canada

Cuba

GuatemalaMexico

PanamaWest Indies

Africa:AngolaBotswanaCongoEgyptKenya

LaumontiteClinoptiloliteMordeniteAnalcimeClinoptiloliteClinoptiloliteLaumontiteClinoptiloliteChabazitePhillipsiteAnalcimeAnalcimeClinoptiloliteLaumontiteClinoptiloliteMordeniteChabazitePhillipsiteAnalcimeClinoptiloliteClinoptiloliteClinoptiloliteMordeniteChabaziteAnalcimeLaumontiteClinoptiloliteMordeniteClinoptiloliteLaumontiteClinoptiloliteErioniteChabaziteAnalcimeClinoptiloliteAnalcimeMordeniteErionite

LaumontiteClinoptiloliteClinoptiloliteMordeniteClinoptiloliteClinoptiloliteMordeniteAnalcimeErionitePhillipsiteClinoptiloliteWairakiteClinoptilolite

ClinoptiloliteClinoptiloliteAnalcimeHeulanditePhillipsiteErionite

xxxx

x

xxxx

xxxxxxxxx

xxxxxxxxx

xx

xxxxxx

xxxxxxxx

x

x

x

xx

x

x

xxxxx

xxxxx

x

xxxxxxxx

xxxx

x

xx

x

x

xx

xx

x

PoorExcellentExcellentPoorGoodPoorPoorGoodGoodGoodPoorPoorPoorPoorExcellentExcellentExcellentExcellentGoodExcellentExcellentExcellentExcellentGoodGoodGoodGoodGoodPoorPoorExcellentExcellentExcellentExcellentExcellentGoodExcellentGood

PoorGoodExcellentExcellentExcellentExcellentExcellentGoodExcellentExcellentExcellentPoorExcellent

GoodGoodGoodGoodExcellentExcellent

149

Table 15.— Reported Occurrences of Sedimentary Zeolites—Continued

Zeolite Minable Minor Chances forCountry species deposit occurrence finding deposit

Northwest Africa AnalcimeMordeniteClinoptilolite

Republic of South Africa AnalcimeClinoptilolite

Tanzania ErioniteChabazitePhillipsiteAnalcimeClinoptilolite

x GoodGoodExcellentPoorExcellentExcellentExcellentExcellentExcellentExcellent

x

xx

xxxxxxx

Asia:IranIsraelPakistanAustralia

ClinoptiloliteClinoptiloliteAnalcimeClinoptiloliteAnalcimeClinoptiloliteLaumontiteAnalcimeClinoptiloliteMordeniteAnalcimeLaumontiteWairakiteClinoptiloliteAnalcimeClinoptiloliteMordeniteLaumontiteErioniteLaumontite

x ExcellentExcellentGoodGoodGoodExcellentPoorGoodExcellentExcellentPoorPoorPoorExcellentGoodGoodExcellentGoodGoodPoor

xxx

x

xxx

ChinaFormosa x

xJapan xxx

xxxxx

KoreaNew Zealand

xxx

xxxxx

Oceania

South Africa:Argentina

x

ClinoptiloliteAnalcimeLaumontiteClinoptilolite

xxx

ExcellentExcellentPoorExcellent

xxChile

Antarctica:Antarctica Laumontite

Phillipsitexx

PoorPoor

thor (59) and R. A. Sheppard of the U.S. Geo-logical Survey, accompanied by a Turkish ge-ologist, with a minimum of field effort. Thisindicates a widespread distribution of such ma-terials in volcanogenic sedimentary rocks inthis country.

face deposits overlain by a few to no more than25 meters of overburden. The zeolite beds areusually flat-lying and vary only slightly in thick-ness along the length of the deposit. Shallowdrilling is usually required to outline the areasof highest grade, but many deposits are minedby simple projection of the bed behind the out-crop, Commonly, the exposed bed can be bro-ken in the mine by bulldozers or rippers; inplaces small amounts of blasting are required.In thinner deposits, care must be taken to elim-inate overlying and underlying clays and vol-canic ash from the ore to preserve purity, butin some of the thicker deposits this poses noproblem,

Mining and Milling

The mining of zeolites in bedded sedimen-tary deposits is a relatively straightforwardprocess requiring only a minimum of equip-ment and trained personnel. Almost all of theknown zeolite deposits being mined are sur-

150

Table 16.—Countries Engaged in Zeolite Mininga

Country M i n e r a l -—

Mines Remarks

United States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mexico . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Cuba . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Korea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Bulgaria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Hungary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Soviet Union . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Yugoslavia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .South Africa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Italy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Germany . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .aAs of 1980

ClinoptiloliteChabaziteErioniteMordeniteMordenite/ClinoptiloliteClinoptiloliteClinoptiloliteMordeniteClinoptiloliteClinoptiloliteClinoptiloliteMordeniteClinoptiloliteMordeniteClinoptiloliteClinoptiloliteChabazite/PhillipsiteChabazite/Phillipsite

12421118521113121

Processing the raw ore is dependent on theenvisioned end use. Water-purification appli-cations require a fine-sand fraction that mustbe prepared from the ore by crushing andscreening whereas fertilizer and animal nutri-tion uses will likely make use of finely pow-dered material. In general, preparation in-volves only crushing, screening, and bagging.Where particle size is critical, the screenedproduct must be washed to remove undersizematerial and then dried. More sophisticated ap-

Agronomic Applications

Many more available.Single deposit, four companies.

Estimated.Estimated.

Estimated.Estimated.Estimated.Several more available.

Numerous, used for construction.Several, used for construction.

plications may require that the zeolite he ion-exchanged to an ammonium or potassium formbefore being shipped to the consumer. In suchcases, the pulverized and screened productmust be subjected to a series of washes withchloride or sulfate salts of these elements,washed with water to e1iminate excess salts,filtered, dried, and bagged. In 1980, crushedore could be produced i n the United States forabout $30 to $40/ton.

DISCUSSION

Although zeolites have been used for manyyears in Japan as soil amendments, they areonly now becoming the subject of serious in-vestigation in the United States as slow-releasefertilizers, moisture-control additives to low-clay soils, traps for heavy metals, carriers ofpest icicles, fungicides, and herbicides, and de-caking agents in fertilizer storage. As soilamendments they appear to retain moistureand i reprove the overall ion-exchange capac-it y of sandy and volcanic soils. Studies are be-ing carried out on both pure zeolite and on zeo-lite that has been pretreated with nutritiveelements, such as potassium or ammonium. In

either case, the zeolite appears to act as a slow-release fertilizer, selectively holding such ele-ments in its structure for long periods of time,thereby increasing the efficiency of such ad-ditives and reducing the total cost of fertiliza-tion. Although the data available are not une-quivocal, the greatest success appears to havebeen with root crops such as sugar beets, car-rots, and radishes, where nitrogen is a vital nu-trient. The optimum level of application, how-ever, must still be determined for various typesof soils and for the particular crop in question,as must the frequency and exact mode of ap-plication, the optimum particle size of the zeo-lite, and the nature of chemical pretreatmentof the zeolite.

151

Table 17 lists organizations that have or areconducting experiments on the use of naturalzeolites in agronomic applications.

Animal Nutrition Applications

Despite the lack of statistical significance, nu-merous studies strongly suggest that the addi-tion of certain zeolite mincrals to the diets ofswine, poultry, and ruminants results in de-cided improvement in growth and in feed effi-ciency (weight gain/pounds of nutritional feedconsumed). In addition, the incidence of intes-tinal disease among young animals appears tobe less when zeolites are part of the daily diet,The most dramatic results have been reportedby overseas workers where experiments mayhave been conducted under conditions thatwere somewhat less sanitary than those gen-erally employed in the United States. Zeolite-supplemented diets appear to be most benefi-

cia1 in swine during the first 30 to 60 days af-ter weaning, although there is some evidenceto suggest that zeolites in the rations of preg-nant sows contributc to increased litter weightsand healthier offspring. In Japan, 2 to 5 per-cent clinoptilolite in the diets of cattle appearedto result in larger animals and fewer incidencesof diarrhea. One study in the United Statesfound a 12-percent increase in feed efficiencyfor cattle during the first 37 days using only1.25 percent zeolite.

The exact function of the zeolites in both die-tary and antibiotic phenomena are not well un-derstood and await serious ph}’biological andbiochemical investigation. The ammonium se-lectivity of clinoptilolite suggests that inruminants it acts as a reservoir for ammoniumions produced by the breakdown of vegetableprotein and nonprotein nitrogen in rations, re-leasing it for a more efficient synthesis intoamino acids, proteins, and other nitrogenouscompounds by micro-organisms in the gastro-intestinal (GI) lumen, From the concentrationof ammonia in the portal blood of weanling ratsfed a 5 percent clinoptilolite diet or dosed oral-1y with this zeolite, Pond, et al. (71), postulatedthat the zeolite bound free ammonia in the GItract, thereby preventing its buildup to toxiclevels in the system. Such an antibiotic effectcould indeed be responsible for the largergrowths recorded for zeolite-fed animals.

Table 18 lists organizations that have or areconducting experiments on the use of naturalzeolites in animal nutrition applications,

Table 17.—Organizations Engaged in Zeolite/Agronomic Investigationsa

Organizations Crop Organization Crop

Department of Horticulture Radishes Agricultural Experiment Station CornColorado State University New Mexico State University SorghumFort Collins, Colorado Las Crucas, New MexicoDepartment of Agronomy Sorghum Department of Plant Science RadishesColorado State University Corn University of New Hampshire CornFort Collins, Colorado Wheat Durham, New HampshireDepartment of Environmental Chrysanthemums Texas Agricultural Experiment Rice

HorticuIture StationUniversity of California Texas A&M UniversityDavis, California Beaumont, TexasU.S. Sugarcane Field Laboratory Sugarcane Department of Soils, Water NitrogenU.S. Department of Agriculture and Engineering retentionHouma, Louisiana Tucson, Arizona in soilsaAs of 1980

152

Table 18.—Organizations Engaged in Animal Nutrition Studies Using Zeolitesa

Organization Animal Organization Animal

Department of Poultry ScienceColorado State UniversityFort Collins, ColoradoDepartment of Animal ScienceColorado State UniversityFort Collins, ColoradoClayton Livestock Research Center

New Mexico State UniversityClayton, New MexicoDepartment of Poultry ScienceOregon State UniversityCorvallis, OregonLivestock Nutrition ServiceWestminster, CaliforniaDepartment of Animal ScienceUniversity of VermontBurlington, VermontU.S. Meat Animal Research CenterU.S. Department of AgricultureClay Center, NebraskaDepartment of Animal SciencePennsylvania State UniversityUniversity Park, Pennsylvania

Chickens

Swine

Beef Cattle

Chickens

Cattle

Ruminants

Rats (swine)

Cattle

Department of Animal ScienceCornell UniversityIthaca, New YorkDepartment of Animal ScienceOregon State UniversityCorvallis, OregonWestern Washington Research and Ex-tension

CenterWashington State UniversityPuyallup, WashingtonDepartment of Animal ScienceUniversity of KentuckyLexington, KentuckyFood and Animal Research, Inc.Juneau, WisconsinDepartment of BiologyCleveland State UniversityCleveland, OhioDepartment of Agricultural EngineeringOregon State UniversityCorvallis, Oregon

Swine

SwineRabbits

DairyCattle

Calves

Calves

ChickensSwine

Odor control

a As o f 1980 .

Excrement Treatment Applications

Although the results are difficult to quantify,almost all studies of the use of zeolites as die-tary supplements in animal rations have re-ported a noticeable decrease in excrement mal-odor and have attributed this observation to thehigh selectivity of the zeolite in the feces forthe ammonium ion. Similar results were notedwhen zeolites were added directly to cattlefeedlots, suggesting that not only can healthierand less odoriferous environments be achievedby the addition of zeolites to animal manure,but that the nitrogen-retention ability of the ma-nure can be improved as well.

Zeolite purification of low-Btu methane pro-duced by the anaerobic fermentation of excre-ment and other agricultural waste products

may be a means of producing inexpensive en-ergy on individual farms or in small commu-nities, and zeolite ion-exchange processes maybe employed in the removal of ammonium ionsfrom recirculating or closed aquacultural sys-tems, thereby allowing more fish to be raisedor transported in the same volume of water.Aquacultural research of this type has been oris being conducted by Becker Industries, New-port, OR; the U.S. Fish and Wildlife Service,Fish Cultural Development Center, Bozeman,MT; Jungle Laboratories, Comfort, TX; the De-partment of Fisheries and Wildlife, New Mex-ico State University, Las Crucas, NM; the Nar-ragansett Marine Laboratory, University ofRhode Island, Kingston, RI; and the Depart-ment of Zoology, Southern Illinois University,Carbondale, IL.

CONCLUSIONS AND RECOMMENDATIONS

Although they have been used locally for sev- tives to animal rations, and in the treatmenteral years in Japan and other parts of the Far of agricultural wastes is still in the experimen-East in small amounts, the use of zeolites as tal stage in the United States. A number of agri-soil amendments, fertilizer supplements, addi- cultural organizations have or are investigat-

153

ing such uses for natural zeolites in thiscountry. The projects have generally beensponsored by grants or contracts from compa-nies that themselves are developing applica-tions for zeolites in one or more areas of tech-nology, or they have been funded by theinstitutions themselves and make use of zeo-lite products provided free or at low cost bythe companies. Table 19 summarizes the agri-cultural research efforts of companies that holdproperties of natural zeolites. In addition,other, nonproperty holding organizations, suchas International Minerals & Chemical Corp.,Cargill, Inc., and Lowe’s, Inc., have also beeninvolved in the development of uses of natu-ral zeolites in agriculture.

Overseas, six to eight agricultural stations inJapan continue to investigate natural zeolitesas soil amendments and dietary supplements;Pratley Perlite Mining Co., which owns a largec1inoptilolite deposit in South Africa, has madeseveral studies of the use of zeolites in the ra-tions of swine and poultry; and a recent Bul-garian-Soviet symposium on natural zeolitescontained seven papers on animal-nutrition ap-plications and two on soil-amendment uses,

‘Second Bulgaria n-%t’iet Symposium on Natu ra] Zeolites,Kardzhali, Bulgaria, Oct. 11-14, 1$)79,

Similar projects are in progress in Cuba andHungary, where deposits of clinoptilolite andmordenite are abundant. The intense interestin the several socialistic countries mentionedabove undoubtedly stems from their efforts touse their own natural resources and therebyreduce their dependency on foreign sources ofexpensive fertilizers and animal rations. Thesesame objectives, of course, are desired by eachdeveloping nation—maximum use of local rawmaterials and minimal use of imported prod-ucts that must be purchased with hard curren-cy. Where they can be found within a particu-lar nation or where they can be obtained fromneighboring countries at minimum cost, nat-ural zeolites have the potential to increase theagricultural productivity of that nation by re-ducing the need for or increasing the efficiencyof chemical fertilizers and animal feedstuffs.

To convert the agricultural promise of natu-ral zeolites into commercial reality, a concertedeffort must be made in the United States andelsewhere by both the private sector and byState and Federal funding organizations. Thestudies to date have been mainly of a prelimi-nary nature—radishes have been grown insteadof potatoes, and rats have been raised insteadof beef cattle—or of limited duration or extent.

Table 19.—Zeolite Property Holders and Zeoagricultural Research Efforts

Organization Zeolite Speciesa Research Effort

Anaconda Company Clinoptilolite, Erionite, In-house; sponsoredChabazite/Erionite, Clinoptilolite, Chabazite, Mor-denite, Phillipsite

Colorado Lien Co. Clinoptilolite SponsoredDouble Eagle Petroleum & Mining Co. Clinoptilolite, Clinoptilolite SponsoredForminco Clinoptilolite NoneHarris & Western Corp. Clinopti/elite/A40rdenite NoneLadd Mountain Mining Co. Erionite/Clinoptilolite NoneLeonard Resources Clinoptilolite SponsoredLetcher Associates ClinoptiloliteMinerals Research

NonePhillipsite None

Minobras, Inc. Erionite NoneMobil Oil Corp. Erionite NoneMonolith Portland Cement Co. Clinoptilolite NoneNL Industries Clinoptilolite NoneNorton Co. Chabazite/Erionite, Ferrierite NoneNRG Corp. Chabazite/Erionite NoneOccidental Minerals Corp. Clinoptilolite, Clinoptilolite, Erionite In-house; sponsoredRocky Mountain Energy Co, ClinoptiloliteUnion Carbide Corp.

SponsoredChabazite/Erionite, Mordenite, Erionite In-house; sponsored

U.S. Energy Corp. Clinoptilolite NoneW. R. Grace & Co. Chabazite/Erionite, Ferrierite NoneaRoman type = working mines, italics = prospects

154

Little information has been developed to illum-inate the long-term benefits or adverse impactson food production. Many of the companiessponsoring this research have considered theresults proprietary, and rightfully so, but work-ers in the field are therefore unable to obtainthe latest information, a situation that often re-sults in massive duplication of effort. Large-scale testing of zeolites under sustained fieldconditions and projects involving statisticallysignificant numbers of animals are greatlyneeded at this juncture. Such projects will re-quire continuous funding by State and Federalagencies, or perhaps, international agencies ifthe results are to be applied to developing na-tions. It would be extremely instructive to carryout such testing in several developing nationsthemselves, where agricultural practices arenot as finely tuned as in the United States.

The actual introduction of natural zeolitesinto specific agricultural processes should poseno major problems. Crushed and sized mate-rial could be added to the fields directly orbanded into the soil either alone or with nor-mal fertilizers using standard equipment. Like-wise, the zeolite could be mixed as a powderor fine granules with normal feedstuffs pro-vided for livestock, or be inserted as a bolusinto the stomachs of ruminants. It could alsobe sprinkled on or mixed with manure accumu-lations on a daily basis for nutrient retentivity.

None of these processes would require spe-cial machinery; in fact, all could be carried outby hand, if such were the common practice inthat country. Users would, of course, need tobe instructed as to the correct amount to ap-ply to fields or to mix with normal rations, andthe optimum time to apply it for specific crops,and considerable educational efforts may benecessary to convince the small farmer of thebenefits of zeolite additives. In this regard, zeo-lites are no different than any innovative pro-cedure that many farmers are slow to accept.

Because the use of zeolites in agriculturalprocesses has not yet reached the proven orcommercial stage, any scenario developed tointroduce this promising technology into de-veloping nations would involve contributions

from both the United States and the develop-ing nations. The contribution of the UnitedStates would be both geological and agricul-tural expertise in zeolite technology, whereasthe contribution of the developing nationswould be a willingness to search for depositsof zeolites and a willingness to carry out somenecessary long-term or large-scale testing un-der field conditions. Any implementation planshould begin with a series of visits by a teamof zeolite experts from the United States toselected developing nations in the world wherezeolites are known or have a high probabilityof occurring. In addition to a leader who wouldhave a broad background in zeolite technology,the team would consist of four to eight geolo-gists, agronomists, animal nutritionists, andagricultural engineers who are not only experi-enced in the use of zeolites in agriculture orin the occurrence of zeolites in volcanogenicsedimentary formations, but who can incite anenthusiasm in others for the wonderful thingsthat zeolites can do. The team would include:

●

●

c

●

a geologist who is not only knowledgea-ble about the occurrence of zeolites in suchenvironments, but who is capable of work-ing with local resource people to find andevaluate potential deposits of zeolites inthese countries;an agronomist or plant scientist with con-siderable experience in the use of zeolitesto improve crop productivity;an animal nutritionist with the necessaryexpertise in the use of zeolites as dietarysupplements in animal nutrition; andan agricultural engineer who has workedwith zeolites in excrement treatment to im-prove the health of confined livestock orthe ammonium retentivity of animal wastes.The agricultural engineer would also pro-vide practical experience to the team.

Prior to the first visit to a developing nation,the team would arm itself with the latest infor-mation in the field by visiting the leading ex-periment stations and research laboratories inthis country and abroad where zeoagriculturalinvestigations are being carried out, Specialemphasis would be placed on the recent workin Japan and in countries of Eastern Europe.

It is vital that the introduction of zeoagricul-ture into a developing nation not end with thevisit of a team of U.S. experts. On the contrary,the initial visit should be folloed up as soonas possible with specific plans for implement-ing the technology into the nation’s agriculturalprocesses. Although the implementation sce-nario of all innovative technologies would ap-pear to be similar from this point on, the zeo-lite scenario would involve a search for thesematerials in the developing nation if such ma-terials had not already been reportrd from thatcountry. Such exploration would probably becarried out by the local geological survey ormining agency, but should be assisted in thefield by a geologist familiar with the occur-rence of zeolites. If zeolites are known in thecountry or if they can be obtained from neigh-boring regions without difficulty, plans shouldbe made with the country's agricultural peo-ple to field test the technology under optimumconditions. Such plans and tests should alsobe made with the assistance of agronomists oranimal scientists already familiar with the useof zeolites in these processes.

-1!

2<

3.

4.

5

6.

7.

0.

9.

10.

11.

12

13.

14,15.

16.

155

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38-846 0 - 85 - 6

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17.

18.

19

20,

21,

22.

23.

24.

25.

26,

27.

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Chapter IX

AgrotechnoIogies Based onSymbiotic Systems That

Fix Nitrogen

Page

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162The Biological Nitrogen Fixation (BNF) Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163Agrotechnologies Based on BNF by Legumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163The Use of Legumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164Inoculant Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164Current Use of Legume-Based BNF Technology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

The Use of Legumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168Inoculant Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

How BNF by Legumes Increases Crop Yields and Soil Fertility . . . . . . . . . . . . . . . . 169Future Potential of Legume-Based BNF Technology . . . . . . . . . . . . . . . . . . . . . . . . . . 172Constraints on Implementation of BNF Technology.. . . . . . . . . . . . . . . . . . . . . . . . . . 173Scenario for Full Implementation of BNF Technology . . . . . . . . . . . . . . . . . . . . . . . . . 176

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

Table

Table No. Page

I. Allocating Funds for a BNF Resource Center . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

Figure

Figure No. Page

l. Pathways for Flow of Nitrogen From Legumes to Other Crops . . . . . . . . . . . . . . . 170

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Chapter IX

Agrotechnologies Based onSymbiotic Systems That Fix Nitrogen

When sustained productivity is sought fromlow-input farming systems, legume crops areespecially attractive because of their ability tobe self-sufficient for nitrogen supply. Life onEarth is dependent on transformations of at-mospheric nitrogen to a form that can be ab-sorbed from the soil by plants and used inprotein synthesis. The process can be accom-plished industrially, but at a very high energycost, Biological nitrogen fixation (BNF) by sym-biotic associations of plants with micro-orga-nisms is more sound economically and envi-ronmentally than using nitrogen fertilizer inagriculture.

Agrotechnology based on BNF by legumeshas two facets: the use of legumes and the useof inoculant technology. Currently, legumesare used in many systems without any specificattempt to maximize their nitrogen fixationthrough inoculant technology. But yields canbe increased and nitrogen fertilizer require-ments reduced by using appropriate inoculanttechnology. Maximum gains from BNF inagriculture will arise from innovative use oflegumes in areas and in roles they have not oc-cupied previously, provided that their modula-tion and nitrogen fixation is assured. Mostlegumes in the Tropics “fix” about 100 kg/ha/year of nitrogen. The common forage tree leu-caena fixes around 350 kg/ha/year and the po-tential for some species is as high as 800 kg/ha/year. Fertilizer savings represent not onlysignificant savings in foreign exchange, butalso reduced dependence on the oil-rich na-tions whose influence over the cost and avail-ability of nitrogen fertilizer is increasing,

The use of legumes involves the managementof legume species in farming systems not onlyfor direct benefits accruing from the multipleuses of legume products and the greater sta-

bility of mixed-cropping, but also for indirectbenefits arising from their ability in some cir-cumstances to make a net contribution of ni-trogen to the soil. This provides nitrogen forcompanion or later nonleguminous crops.

The objective of inoculant technology is tointroduce sufficiently high numbers of pre-selected strains of rhizobia that they have acompetitive advantage over any indigenous soilstrains of lesser nitrogen-fixing ability into thevicinity of the emerging root. Inoculation tech-nology involves: selecting strains of rhizobiathat are compatible and effective nitrogen-fixers with particular legumes; multiplyingselected strains to high population densitiesin bulk cultures; incorporating the liquid rhizo-bial cultures into a carrier material [usuallyfinely milled peat) for packaging and distribu-tion; and finally, coating the seeds of legumeswith the carrier or implanting the soil with theinoculant.

Legumes already are used widely and con-sistently, though as minor crops, in farmingsystems of the Tropics. Inoculant technologyis used on a meaningful scale only in a fewcountries other than the United States and Aus-tralia. Great future potential rests in the devel-opment of:

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legume-based pastures and viable multiple-cropping systems including legumes forunder-used savannahs;agroforestry systems that combine fast-growing, nitrogen-fixing trees, legumes,and other crops to meet the food and fuelrequirements of the rural poor;fast-growing leguminous trees for reforest-ing water catchment areas following for-est clearance;

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legume-based cropping systems to givesustained productivity in cleared junglesoils which typically exhibit a rapid de-cline in fertility under conventional crop-ping; andselection of deep-rooted, drought-tolerantleguminous tree-s that can serve as browsespecies in the world’s dry lands.

The major constraints to full implementationof legume-based BNF technology in the Trop-ics relate to the delivery and acceptability ofthe technology at the farm level. The con-straints are political, cultural, socioeconomicand, to a lesser extent, scientific. The majorscientific constraint is inadequate understand-ing of host legume, rhizobial strain, and envi-ronment interactions. This results in an in-ability to predict whether a given legume willrespond to inoculation in a particular regionor not. A constraint on better understandingof these interactions is the lack of trained per-sonnel to execute legume inoculation trials todetermine the economic benefits. A lack of do-mestic inoculant production plants also con-strains research, development, and productionenterprises.

Legume-based BNF technology would ben-efit

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from:

increasing economic and political pressurefor greater energy efficiency in agriculture;increased recognition by decisionmakersin funding agencies and in governmentsof the potentials for exploiting BNF in de-veloping country agriculture;an increase in trained professionals andtechnicians in tropical countries;improved integration of legume germ-

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concerted application of international fund-ing to establish a BNF Resource Center(this Center could be staffed, equipped,and budgeted to provide technical assis-tance; offer germplasm and informationservices; provide professional and techni-cal training; conduct research necessaryto adapt BNF technology to individual de-veloping countries when it is beyond thecapability of local researchers);improved opportunity to exchange find-ings from field research programs; andimplementation of a sequence of standard-ized experiments designed to quantify theeconomic yield benefit attributable to leg-ume inoculation under field conditionsand followed by studies to quantify the ni-trogen balance in multiple cropping sys-tems that include legumes.

Legume inoculation does not substantially af-fect the need for farm labor. The inoculationis accomplished as an integral part of the sow-ing method whether by hand or mechanizedplanter. If fertilizers are normally applied, elim-ination of the need for nitrogen reduces thecapital cost but no substantial labor saving isrealized as other fertilizers still need to be ap-plied. The use of legumes to benefit companionor following crops is consistent with the farm-ing systems already prevalent in the Tropics.To use legume-fixed nitrogen for, as an exam-ple, cereal production in the United Stateswould necessitate adoption of mixed-croppingsystems that are not easily mechanized. Thus,an increased demand for labor would be an im-pact. The major positive impacts of BNF tech-nology are indirect through elimination of themultitude of negative environmental impacts

plasm improvement programs and legumebacteriology programs;

associated with nitrogen fertilizer production,distribution, and use in agriculture.

INTRODUCTION

Beans and peas are well-known examples of terns. This is because of their unusual abilityfood products from the array of plant species to be self-sufficient for nitrogen supply. “that belong to the legume family. Legumes areespecially attractive when sustained produc- Nitrogen is an essential component of all lifetivity is sought from low-input farming sys- forms; it is a cornerstone in the chemical struc-

163

ture of proteins, Ironically, nitrogen is abun-dant in the atmosphere—the air we breathe is80 percent nitrogen. In its gaseous form, how-ever, nitrogen occurs as dinitrogen molecules,each having two nitrogen atoms joined by a tri-ple bond. This is among the most stable, inertmolecules known and cannot be used directly,Thus, life on Earth is totally dependent ontransformations of atmospheric nitrogen to aform in which it can be use readily by plants,and subsequently, by animals and man.

This process is referred to as “nitrogen fix-ation” and involves splitting dinitrogen intotwo nitrogen atoms that are then reacted withhydrogen (generated by splitting water mole-cules) to form first ammonia and subsequently

a range of nitrogenous compounds. Nitrogenfixation can be accomplished industrially, butthe process is one of the most energy demand-ing in today’s agriculture. The energy cost offixing nitrogen in the form of urea, ammoniumsulfate, or ammonium nitrate is compoundedby the additional costs involved in transportand application. Additionally, the rather smallproportion of nitrogen-fertilizer actually takenup by the crop to which it is applied and theserious environmental pollution that can becaused by nitrogen lost from agricultural landthrough run-off are incentives for appraisingalternate nitrogen-sources. Self-sufficiency fornitrogen supply as exemplified by the legumesis thus a highly desirable trait.

THE BIOLOGICAL NITROGEN FIXATION (BNF) PROCESS

Biological nitrogen fixation (BNF) in legumesis possibly because of the mutually beneficialassociation (symbiosis) that can form betweenleguminous plants and certain micro-orga-nisms from a specific family of soil bacteriaknown as Rhizobium. Rhizobia can penetratethe roots of legumes and give rise to highly spe-cialized organs referred to as root nodules.These are quite different from tumors or otherswellings that commonly occur on plant rootsas a result of infection by disease-causing (path-ogenic) organisms. The structure and functionof nodulated legumes is modified in such a waythat carbohydrates (sugars) produced in theleaves of the plant during photosynthesis aredelivered to the nodulated root where they arerespired to provide energy. In the nodules, thisenergy is consumed during nitrogen fixationand it is used to sustain the growth require-ments of the rhizobia.

Gaseous dinitrogen enters the nodule fromthe air spaces in the surrounding soil. An en-zyme, nitrogenase, that is the unique contribu-tion of the microsymbiont, catalyzes the split-ting of dinitrogen molecules and the reactionof their component atoms to form ammonia.Neither the sequence of reactions and transfor-mations that follow initial fixation nor theprecise sites in the nodule where the events oc-cur are fully understood. The steps involve veryrapid incorporation of ammonia, which wouldordinarily be toxic to both symbionts, into ni-trogenous compounds such as amino acids,amides, and/or ureides depending on the par-ticular legume species. These are used through-out the ‘plant as building blproteins,

ocks for plan

Most farmers in the Tropics do not know that variably include legumes (52,59), Thus, legumelegumes fix nitrogen. Yet, traditional and mod- cultivation happens because farmers overern farming systems of the Tropics almost in- many centuries have recognized that legumes

164

are valuable components in farming systemsrather than from intentional exploitation of bio-logical nitrogen fixation per se.

Agrotechnology based on BNF by legumes,therefore, has two major aspects. One relatesto the deliberate inclusion of legumes in crop-ping systems to derive benefits from their ni-trogen fixation. The other concerns the inten-tional use of specific practices to maximizenitrogen fixation by legumes. For conveniencethese two facets of BNF technology will be re-ferred to as “use of legumes” and “inoculationtechnology. ” The distinction is drawn to em-phasize that currently legumes are used widelywith less than maximal benefits because of de-ficient symbiotic associations. Productivity

could be increased by using appropriate tech-nology to assure effective symbiotic nitrogenfixation by legumes. Much greater gains in pro-ductivity and economies of energy can berealized from reduced fertilizer requirementsthrough innovative use of legumes in roles theyhave not occupied previously in productionsystems (e. g., the use of fast-growing legumi-nous trees in agroforestry systems). Productiongains will be greatest if the use of legumes isalways complemented by appropriate inocu-lant technology. This is because legumes canonly benefit fully from biological nitrogen fix-ation if they encounter rhizobia with whichthey are genetically compatible.

THE USE OF LEGUMES

The benefits from BNF through the use oflegumes in farming systems are both direct, be-cause the legume has an intrinsic value, andindirect, because inclusion of a legume affordsgreater yield stability in adverse growth con-ditions and can benefit companion or follow-ing nonleguminous crops.

Direct benefits from BNF by legumes in crop-ping systems arise from the multiple uses ofplants in the legume family. Though knownprimarily for grain, forage, or feed production,legumes are also cultivated in the Tropics fortimber, fuelwood, green manures, oils, fibers,gums, drugs, dyes, and resins. Additionally,they may be used as hedges; ground covers forweed, insect, and disease control; as soil sta-bilizers on terraced slopes; or simply for shadeor as ornamental (59).

Indirect benefits accrue from the stability ofperformance and assurance of some economicreturn for at least one component under un-favorable conditions when legumes are inter-cropped with other crops. Stability is afforded,for example, in erratic rainfall zones when thecomponents in the intercropping system areseparated in time such as with sorghum/pigeonpea and groundnut/cotton (59,56). When thereis an outbreak of pests or diseases, maize/beansand other intercrops afford stability of yieldsand income (3,32). Other indirect benefits ac-crue from the ability of legumes to make a netcontribution of nitrogen to the soil under somecircumstances, thereby reducing the nitrogen-fertilizer requirements for a companion or fol-lowing nonleguminous crop.

INOCULANT TECHNOLOGY

There is a commonly held view (2) that trop- without inoculation (49,30). This view is noical legumes are much more promiscuous than longer well-founded. Some species and acces-temperate legumes—that they nodulate freely sions from genera previously considered to bewith a wide range of tropical rhizobia and that promiscuous (2) require specific strains oftropical soils are laden with so many bacteria Rhizobium (9,28,26) or form highly effectivethat effective modulation is virtually guaranteed symbioses with only a few out of the wide ar-

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ray of strains with which they nodulate (69,16,22). Recent intensification of interest in thetropical legumes and their rhizobia is reveal-ing much greater variation in genetic compat-ibility and nitrogen fixation effectiveness thanhas generally been acknowledged (38,23), Aplea has been made for recognition that tropi-cal legumes fall into one of three categories(23).

c Promiscuous effective (PE) group, wheremodulation occurs with a wide array ofrhizobia isolated from many legume gen-era and the resultant symbioses are pre-dominantly effective in nitrogen fixation.

● Promiscuous ineffective (PI) group, wheremodulation occurs with an array of strainsof rhizobia isolated from many legumegenera, but where fully effective symbiosesform with only a few of those strains.

c Specific (S) group, where those strainsfrom the same genus (or a restricted num-ber of other genera) form effective sym-bioses.

Just as with the temperate legumes, the like-lihood that compatible, effective rhizobia willnot always be present in sufficient numbers inthe soil microflora is the rationale for using in-oculation technology for tropical legumes (24).When a tropical legume seed is sown uninocu-lated in a tropical soil, a native rhizobial pop-ulation of strains differing greatly in their sym-biotic effectiveness compete for the finitenumber of modulation sites on the legumeroots. Many forage legumes bear only 10 to 20nodules on which they depend for nitrogenduring the first three months of their establish-ment. Thus it becomes critically important thateach of the nodules that form on the root con-tain a strain of Rhizobium that is fully effec-tive in fixing nitrogen. The underlying objec-tive in inoculation technology is to introducesufficiently high numbers of preselected strainsof rhizobia into the vicinity of the emergingroot that they have a competitive advantageover any indigenous soil strains of lesser ni-trogen-fixing ability in the formation of root-nodules.

Inoculation technology involves:

selecting strains of rhizobia that are com-patible and effective nitrogen-fixers withparticular legumes;multiplying selected strains to high popu-lation densities in bulk cultures;incorporating the liquid rhizobial culturesinto a carrier material (usually finelymilled peat) for packaging and distribu-tion; andfinally, coating the seeds of legumes withthe carrier or implanting the soil with theinoculant directly into the seed drill (64,14,25).

An inoculum strain of Rhizobium recom-mended for a particular host must be able toform effective nitrogen-fixing nodules with thathost under a wide range of field conditions. Ni-trogen fixation effectiveness is only one impor-tant criterion for an inoculant strain. Othercriteria include: competitiveness in nodule for-mation, particularly against less effectivestrains; persistence in the soil in the absenceof the host, especially for strains for annual spe-cies; promptness to form nodules; ability to fixnitrogen under a range of soil temperature con-ditions; tolerance to pesticides; tolerance of lowsoil pH; modulation in the presence of high lev-els of soil nitrogen; and ability to grow and sur-vive in peat inoculants.

The host genotype interacts with the infect-ing strain of Rhizobium in determining thelevel of nitrogen fixation, with the host play-ing the dominant role. Thus, two sources ofvariation (plant and Rhizobium strain) can beexploited in selection programs, Most com-monly, though, the plant is selected independ-ently and a suitable strain sought thereafter,thus allowing only for exploitation of strainvariability. The range of specificities of hostgenotype interactions is well-illustrated by soy-bean (77) and in the African clovers (51).

Three approaches to select strains for inoc-ulants exist: select numerous inoculants, eachwith a highly effective strain for individual spe-cies; select “wide-spectrum” strains that vary

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from good to excellent in nitrogen fixation witha range of legumes; or select multiple-strain in-oculants containing the best strain for eachhost species. There may be a conflict betweenthe option that would be chosen for commer-cial expediency and that which is scientificallypreferred (25). In Australia, “wide-spectrum”strains are used when these are available, butthere is increasing use of specialized inoculantswith specific strains for individual hosts. De-spite findings that suggest that multi-strain in-oculant should be avoided because of possibleantagonistic and competitive effects (46) andcompetition in nodule formation from the lesseffective strains (17) this is the approach usedsuccessfully by the U.S. inoculant industry.

Strains for testing can be obtained from otherlaboratories working with the same species,from nodules on plants in the native habitatfrom which they were originally collected, andfrom nodules formed on the legume by nativestrains after sowing uninoculated seed in theregion where the new species is expected tobe used. None of these sources is invariably bet-ter in screening programs.

Most legume inoculants are prepared by add-ing liquid cultures of rhizobium to a finelyground carrier base material such as peat. Al-though mixtures of peat with soil or compostmixtures, lignite, coir dust, and some otherorganic materials have been used, peat hasproven to be the most acceptable carrier world-wide. Agar, broth, and lyophylized cultures arenot recommended because survival rates forthese forms are poor (20,21,72).

Peat cultures can be prepared in two ways.Either ground (milled) peat is mixed with ahigh viable count (more than 109 rhizobia/ml)broth culture in sufficient volume to providethe minimum number of rhizobium acceptablefor use, or sterilized peat is inoculated with asmall volume of culture and incubated to allowmultiplication of the rhizobia. The choice ofmethod will depend on two factors—the sur-vival of the rhizobia in peat in numbers highenough to meet a minimum standard of quality,and the availability of suitable, sterilizable con-tainers and sterilizing facilities. The two fac-

tors that most affect survival of rhizobia in peatare temperature of storage and sterility of thepeat. There are differences among species andalso between strains of the same species ofRhizobium in their ability to survive well inpeat (63).

Like all biological products, legume inocu-lants are prone to loss of quality because of var-iation in the organism and from unforeseenfactors affecting some aspect of growth or sur-vival. It is therefore essential that a quality con-trol system be established. In Australia, large-scale manufacture of legume inoculants is byprivate enterprise and a separate, official (gov-ernment) control laboratory is responsible formaintaining a high-quality product. The con-trol laboratory maintains and supplies recom-mended strains of Rhizobium to the industry,checks strains annually for ability to fix nitro-gen, assesses quality of cultures during andafter manufacture, and conducts any researchthat is necessary to overcome problems asso-ciated with production and survival. In theUnited States, the industry is free to select itsown strains and official control ensures thatthe product can form nodules on the legumefor which it is recommended.

Although control of inoculant quality is pri-marily in the manufacturer’s interest and there-fore his responsibility, control by external bod-ies provides protection from less scrupulousoperators and genuine failure of a strain out-side manufacturer control. Not all countriesback their control labs with legislation. A con-trol group requires suitably qualified and ex-perienced personnel with facilities to permitnormal aseptic culture transfer and plantgrowth facilities suitable for legumes frommany environments. Methods of assessmentinvolve both qualitative and quantitative tests.The number and extent of these may vary ac-cording to competence and experience of man-ufacturers and the standards desired. In Aus-tralia, this control extends to holding stocks ofthe strains used in inoculants. This is not thecase in the United States (29,70). In additionto assessment of quality throughout manufac-ture, it is important to monitor product qualityin retail outlets. Standards acceptable at this

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level may vary between countries. It is impor-tant that standards be realistic and within thecapability of manufacturers yet ensure that suf-ficient viable rhizobia are applied to the seedto provide a satisfactory inoculation. In manyinstances this can be as few as 100 rhizobia perseed but in cases of severe environmental stressas high as 10,000 or even 500,000 (1 1,12,21),

The prime objective of inoculation of legumeseed with rhizobial inoculants is to induce nod-ulation of the introduced legume host plant.Rhizobia introduced into new environmentsmust live saprophytically in competition withother rhizobia and soil micro-organisms in anenvironment that may be adverse for theirgrowth and survival until the host seedlingroots provide the ecological niche to whichthey are adapted. Thus, steps should be takento help inoculant strains: remain viable untilthe host seedling is at the susceptible stage forinfection; compete with any natural rhizobiafor infection sites on the roots of the host leg-ume and permit maximum nitrogen fixation;nodulate its host promptly and effectively overa range of environmental conditions; and per-sist in the soil for at least several years in suf-ficient numbers to maintain modulation ofperennial legumes or to achieve prompt nodu-lation of regenerating annual species.

The first attempts at inoculation involvedtransferring soil from one field to the next, butwhen the organisms responsible for nodule for-mation were isolated, artificial cultures soonreplaced the laborious soil transfer technique,The usual inoculation technique is to apply theinoculant to the seed just before sowing eitheras a dust or as a slurry with water or adhesivesolution. Adhesives such as gum arabic or cell-ulose not only ensure that all the inoculumadheres to the seed but also provides a morefavorable environment for survival of the in-oculum. Pelleting of seed with finely groundcoating materials such as lime, bentonite, rockphosphate, and even bauxite (11,12) have beenused to protect rhizobia during their time onthe seed coat. pelleting is a simple on-farmtechnique (11,50) but custom-pelleted (by seeds-men at farmer’s request) and preinoculatedseed is now more popular. This latter proce-

dure is potentially able to provide high popu-lations of rhizobia on the seed for a long periodof time (one growing season to the next) buthas not yet been fully developed or exploited.

Most preinoculation procedures arc based onmultiple coatings, alternately of adhesive andfinely ground pelleting materials as used insimple pelleting, The peat inoculant is includedas one (or more) of these coating layers. Soak-ing seeds in a broth suspension and then ex-posing them to either high pressure or vacuumto impregnate the rhizobia into or below theseed coat has not proven successful. Theoreti-cally, rhizobia introduced in this way wouldbe protected from drying and other adverse en-vironmental conditions, but the quality of prod-ucts produced commercially has been variableto very poor (16,10,66). It is, in fact, an indict-ment of the research workers in this area that25 years has yielded so little progress in an areawhere there is so much potential,

These production techniques are particularlyapplicable to less well-developed and inexpe-rienced rural groups, If high-quality and relia-ble products were marketed by a manufactureror seeds distributor, the farmer would not needto be involved in legume inoculation.

A recent alternative to pelleting and pre-inoculation has been the use of concentratedliquid or solid granular peat culture that canbe sprayed or drilled directly into the soil withthe seed during planting. Suspensions of rhizo-bia either as reconstituted frozen concentratesor suspensions of peat inoculant can be appliedwith conventional equipment. Similarly, gran-ulated peat inoculants can be drilled in fromseparate hoppers on the drilling equipment.These methods have been especially successfulfor introducing inoculant strains into situationswhere there are large populations of competingnaturally occurring soil rhizobia (6), in casesof adverse conditions such as hot-dry soils (68),and where insecticide or fungicide seed treat-ment precludes direct seed inoculation (67,12).Solid inoculant, also known as granular or “sodimplant” inoculum, is advantageous also, whereseeding rates for crop legumes of 70 to 100kg/ha make on-the-farm inoculation logisticallyimpracticable.

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CURRENT USE OF LEGUME-BASED BNF TECHNOLOGY

The Use of Legumes

Grain legumes are cultivated widely in a va-riety of agro-climatic zones in the Tropics andSubtropics. Total area in grain legumes in 1979was 175 billion hectares. Dry bean (Phaseolusvulgaris) is the most important grain legumein Latin America, groundnut (Arachis hypo-gaea) in Africa and collectively groundnut,piegeon pea (Cajanus cajan) and chickpea(Cicer arietinum) in Asia. These and othergrain legumes have been consistent compo-nents of human diet in the Tropics for centu-ries, yet in quantitative terms they continue tobe minor crops.

The use of legumes in mixed legume/grasspastures in the Tropics is at present restrictedto northern Australia, the United States (Ha-waii, Florida), southern Brazil, and northeast-ern Argentina. The total area in improved leg-ume/grass pasture is insignificant compared tothe area of native grasslands under grazing.The use of temperate forage legumes in mixedpastures at high altitude locations in develop-ing countries is frequent but is outside thescope of this report.

Production statistics for tropical grain leg-umes are seldom accurate. Most of the produc-tion is on a subsistence scale on small farmsand the yields are seldom included in officialstatistics. Thus, a figure of 186 million tons (31)should be regarded as an understatement.

There are many agencies supporting andconducting research related to the use of leg-umes. International agencies such as FAO,UNDP, IBPGR, and the IARCs all have grainand forage legume programs. USAID, togetherwith the governmental agencies of many coun-tries, engaged in foreign agricultural develop-ment support research on legumes. The worldBank and several private and public founda-tions also support legume research. The authoris not aware of any country in the Tropics thatdoes not have a legume project within its offi-cial agricultural program. Additionally, univer-sities and agricultural colleges in tropical coun-tries usually have legume programs. These

projects cover the physiology, plant nutrition,agronomy, pathology, entomology, breeding,and seed production of legume crops. Insofaras BNF proceeds at a rate governed stronglyby the plant’s ability to deliver carbohydrateto its root nodules, most technologies that im-prove overall plant performance are likely tohave a beneficial impact on modulation and ni-trogen fixation. Relatively few projects, how-ever, give adequate attention to specific tech-niques for maximizing BNF by the respectivelegume. In fact, some research programs withlegumes are conducted under nitrogen-ferti-lized conditions or in fertile, nitrogen-rich soils.Breeding for high-yielding varieties under suchconditions has resulted in plant types that areonly weakly symbiotic and heavily dependenton soil nitrogen.

Given the important role of grain legumes asthe major dietary protein source for low-in-come groups in the developing countries, it ishardly surprising that such a multitude of fund-ing agencies and implementing organizationsgive attention to research on legume technol-ogy. While it is to be expected that there willbe overall gains in the amount of nitrogen fixedfrom improved performance by legumes in theroles, and on the acreage they currently oc-cupy, the major gains in BNF will follow in-creases in the total land area where legumesare grown and especially the innovative use ofhitherto underutilized legumes.

lnoculant Technology

Inoculant technology is used widely on acommercial scale in the developed countries.The United States and Australia have substan-tial industries to produce, distribute, and mar-ket legume inoculants. There is also commer-cial-scale production in Brazil, Uruguay,Argentina, India, and Egypt, Inoculants areavailable commercially in many other coun-tries but they are produced in U.S. or Austra-lian laboratories. Some research centers, suchas CIAT and the University of Hawaii NifTALProject, produce inoculants in pilot-scale plants

as a service to researchers and occasionally tolegume growers. Demands for inoculation tech-nology are increasing, primarily because of theincreased use of soybeans.

There are dangers in trying to satisfy this de-mand by importing inoculants developed in theUnited States or elsewhere. This is because pre-sent inoculation technology has not proventransferable. That is, strains of Rhizobium andinoculation methods developed for conditionsat one location in a particular farming systemdo not perform equally well at another loca-tion in a different farming system. Further-more, the viability of rhizobia in legume in-oculants is great ly affected by storageconditions during shipment. Since producersare unable to control such factors, no guaran-tee can be given that the inoculants are of mer-chantable quality on arrival at their destination.For both these reasons inoculation failures area common occurrence and this is harming con-sumer acceptance of the technology. An idealscenario for improved implementation of BNFtechnology is described in a later section.

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The organizations funding research to adaptinoculant technology to the circumstanceswhere it will be used in tropical countries in-clude: UNDP by its support to the IARCsthrough CGIAR and for a specific research pro-gram involving IITA and BTI/Cornell Univer-sity; UNEP and UNESCO support inoculanttechnology under the MIRCEN Project; FAOis actively considering the role it might playin the adaptation of inoculant technology foruse in developing country agriculture; USAIDthrough its contracts with University of Hawaii(NifTAL Project) and USDA, Beltsville ARC(World Rhizobium Study and Collection Cen-ter) through grants under Section 211(d) to theU.S. Universities’ Consortium on BNF in theTropics, and through a portfolio of small grantsadministered by USDA SEA/CR; USAID andseveral governmental and nongovernmentalagencies that support the CGIAR are therebysponsoring work at CIAT, IITA, ICRISAT, andICARDA on the adaptation of inoculant tech-nology for use in the Tropics.

HOW BNF BY LEGUMES INCREASES CROP YIELDSAND SOIL FERTILITY

Consider the possible pathways to transfernitrogen from legumes to other crops (figure1), The relative importance of the transfer path-ways of nitrogen from legumes to other cropsand/or the soil can be estimated. Nitrogen gainsper hectare per year entering the cycle as seeds(1 to 2 kg) (41) and in acid rainfall (1.5 to 3.5kg) (78) are small compared to the nitrogenfixed biologically. About 50 percent of the ni-trogen accumulated in legumes in fertile soilsis attributed to BNF (71), though the propor-tion from fixed nitrogen will be greater in im-poverished soils and lesser under nitrogen fer-tilization. Nitrogen accumulation in legumemonocrops ranges from 50 to 350 kg/ha/year,It is generally accepted that nitrogen fixationof around 100 kg/ha can be expected from themajority of grain and forage legumes. Higher

levels are possible for leucaena and other for-age legumes with a 12-month growing season.Low levels are likely for bad nitrogen fixerswith short growing seasons (e. g., Phaseolusvulgaris).

As an example, follow the fate of 100 kg ofbiologically fixed nitrogen entering the cycle.Between 60 and 90 percent of the nitrogen ac-cumulated in legumes is removed as grain—depending on the species, harvest index, andharvesting practice, or as animal products de-pending on the intensity and selectivity of graz-ing. Thus, in an intercropping system only 10to 40 kg nitrogen could potentially benefit othercrops. Some of the organic nitrogen of the leg-ume residues is mineralized rapidly. The restis added to the soil organic matter pool and it

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Figure

is mineralized slowly over a much longer pe-riod, Studies show that 60 percent is probablythe maximum portion of the nitrogen in the or-ganic residue of a legume crop that could bemineralized in time to benefit a following crop.

If 50 percent of the nitrogen is used in theinitial mineralization, in a cropping systemwhere the legume fixes 100 kg/ha/year only 5to 20 kg of nitrogen is likely to benefit the fol-lowing crop, One practice that could substan-

tially increase the contribution is green manur-ing. If one year’s production were incorporatedinto the soil, it would leave a residual benefitof 50 kg/ha/year for the following crop. Experi-ence has shown, however, that crops do notnecessarily respond to exaggerated applica-tions of green manures.

There are few farming systems where greenmanuring is economically feasible (41,8) sinceland is tied up without immediate economic

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return. Where green manuring is practiced, 5tons of green matter per hectare is an acceptedapplication rate (54). This would represent anaddition of only 40 kg/ha of nitrogen to the soil,of which only about 20 kg would mineralizeto the benefit of the crop. Green gram contrib-uted 22 kg of nitrogen to following crops andcalapo/stylo green manure contributed 15 kg(l).

The situation is more complex in mixed crop-ping systems where the legume and nonlegumeare growing concurrently. Legumes usuallytake up less soil nitrogen in competition withnonlegumes and a greater fraction of the ni-trogen they accumulate in a mixed crop is fromfixed nitrogen. Somewhat surprisingly, the ni-trogen fixation of intercropped beans (Phase-OlUS vulgaris) per hectare is not significantlydifferent from beans raised in monoculture(36). This is attributed to competition betweenthe maize and the bean for light and nutrientsbeginning after the decline in nitrogen-fixingactivity in the bean’s root nodules. Not all leg-umes shut down nodule function as early inthe growth cycle as Phaseolus vulgaris but theeffect of intercropping on nitrogen fixationmay be detrimental in other intercroppingsystems.

It is a common misconception that there issubstantial direct transfer of nitrogen from thelegume to a nonlegume companion species ina mixed cropping system. There is no convinc-ing evidence that actively growing, healthy leg-umes, whether grain or forage, excrete signif-icant amounts of nitrogen from their roots ornodules. The hypothesis originally proposed byVirtanen and coworkers (73,74,75) that surfaceexcretion of simple amino compounds fromhealthy, functioning legume root-nodules re-sulted in direct transfer of significant quantitiesof nitrogen to nonlegume companion specieshas found little support from other workers(45,7,47,80,81).

Subsequent research under carefully con-trolled conditions using the “fox box” tech-nique (18) indicated that excretion of a widerange of substances from plant roots does oc-cur, but that the quantities involved are small,less than 0.5 percent of the plant’s nitrogen (65).

Stated differently, a crop fixing 100 kg of ni-trogen a year would excrete only 0.5 kg to thesoil.

Nitrogen benefit to nonleguminous cropsthrough association with companion legumespecies is considered to be of an indirect naturethrough loss and decay of shoot, root, and nod-ule tissue, or by recycling via the grazing ani-mal, rather than by a direct pathway (76,15,29,79),

Clearly then, mixed cropping systems thataim to use legume-fixed nitrogen for the bene-fit of a companion nonlegume species mustmatch species so that the nonlegume is longer-lived than the legume. Nitrogen will be releasedin significant amounts only after cessation ofactive growth and decomposition of tissues ofthe legume. The maize/bean association usedwidely in Latin America shows this principal.Beans fix about 20 to 40 kg of nitrogen pergrowing cycle (34). Assuming 70 percent re-moval of nitrogen as protein in the legumegrain, this leaves only 6 to 12 kg in legumeresidues, of which 3 to 6 kg (assuming 50 per-cent mineralization) will be mineralized in timeto benefit the maize. Some estimates place themineralization that can benefit a companionspecies as low as 20 percent. Consistent withthis, it is not uncommon for there to be no de-tectable nitrogen benefit in companion cropsthat are intercropped with legumes.

It is evident that the BNF benefit to nonleg-umes due to inclusion of legumes in a croppingsystem is small compared to the level of nitrog-enous fertilizer used in the more intensive ce-real production systems of the developedworld. Thus, the principal contribution of BNFto human nutrition will continue to be via theprotein in legume grains. Any suggestion ofsubstantial replacement of nitrogen fertiliza-tion of cereals and root crops by biologicallyfixed nitrogen is unrealistic because thesecrops respond to levels of nitrogen fertilizer fargreater than those currently supplied throughBNF by legumes, Thus, there is an urgent needto devise ways to increase the contribution thatBNF by legumes can make to cropping systemsas a complement to nitrogen fertilizer-basedproduction, rather than as an alternative to it.

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Legumes can be managed to increase theirnitrogen contribution. They vary in total nitro-gen fixed, the proportion retained in non-har-vested residues, the percentage nitrogen levelin residual tissue, and the facility with whichthe organic nitrogen is mineralized. Thus,some species, managed in particular ways, willgive greater residual nitrogen benefits. Giventhis, the priority now given in legume breedingprograms to improving their harvest index, i.e.,maximizing the fraction of each plant’s totalproduction that is removed as grain, should becalled into question.

In summary, the principal benefits from BNFthrough the use of legumes in farming systemsin the Tropics are derived from the dietary pro-tein of the legume grain, the multiple uses thatlegumes serve for the subsistence farmer, andthe greater stability of yield and financial re-turn of intercrops over monocrops. The indi-rect benefits from contribution of biologicallyfixed nitrogen to companion or following spe-cies are small but are significant in the con-text of input levels in subsistence farming.

Insufficient reliable data exist on the poten-tial benefits from enhancing, through inoculanttechnology, the nitrogen fixation in tropicallegumes. It is tempting to recommend rhizobialinoculation of all legume sowings as an insur-ance measure against the risk of modulationfailures that would otherwise occur. However,inoculant technology does represent a cost, al-beit small, and does add a degree of complex-ity to the sowing practice. Thus, inoculant tech-nology should only be advocated when thereis a known need to inoculate and a demonstra-ble benefit. Additionally, the concept and prac-

tice of inoculant technology is so foreign to thefarmer’s normal practices that it should not berecommended lightly. A subsistence farmercan be forgiven for not comprehending nor ac-cepting a technology that involves stickingblack powder containing bacteria to his seeds.This contradicts concepts which he had onlyrecently learned, namely, that bacteria are badand clean seed is important. It is to be ques-tioned whether inoculant technology in thisform will ever be accepted widely among sub-sistence farmers in the Tropics and Subtropics.

Unfortunately, many trials performed to eval-uate inoculant technology with tropical leg-umes under tropical conditions have been donewith imported inoculants that may not havecontained acceptable levels of viable rhizobia.Lack of response to inoculation in such trialsdoes not preclude the possibility that the leg-ume could potentially benefit from inoculation.More recently, coordinated networks of trialshave been initiated to determine whether thereis an economic yield benefit from inoculationof legumes or not. INTSOY conducts interna-tional Soybean Rhizobium Inoculation Exper-iments (ISRIE) throughout the Tropics. CIATdistributes an International Bean InoculationTrial (IBIT) throughout Latin America. TheUniversity of Hawaii coordinates an Interna-tional Network of Legume Inoculation Trials(INLIT) offered for 13 agriculturally importantlegumes and involving a three-stage experi-mental program where cooperators through-out the Tropics select strains specifically fortheir legume variety and local soil conditions,thereby maximizing the opportunity for a yieldresponse following inoculation.

FUTURE POTENTIAL OF LEGUME-BASED BNF TECHNOLOGY

Despite their seeming attractiveness for sus- use of nitrogen fixed biologically by legumes?tained productivity from low-input production A small-scale, subsistence farmer elects to raisesystems, and despite also their consistent stra- those crops that best meet his household’stegic use in many farming systems of the Trop- needs but he also chooses one crop, at least,ics, legumes have remained minor crops in the to sell or exchange for goods or services. Large-systems where they occur (52). Why is this the scale farmers consider the economic returncase, and what factors would lead to greater and ease of management associated with the

crops they plant. A grower preference for ce-reals over legumes, when the grain is to be mar-keted, would be understandable. It is usual foryields of cereal grains to be as much as fourtimes higher than legumes (typically 3.0 t/havs. 0.7 t/ha), Although the protein content i smuch higher in legumes (30 percent) than incereals (6 percent), the market value of legumegrains, albeit higher than for cereals, does notcompensate the grower for their low relativeyield.

Many factors will contribute to an increasein the use of legumes. Cereals will continue tobe the major source of protein and calories forhuman nutrition worldwide, but an increasein importance of root and tuber crops and plan-tains over the next two or three decades is an-ticipated (58). Legumes can be expected to beone means of complementing the dietary qual-ity of these starchy protein-deficient foods.

Another factor that has already caused a re-appraisal of biological ni t rogen f ixat ionthrough legumes is the cost and availability ofenergy to produce nitrogen fertilizers. Already,20 percent of nitrogen fertilizer production inthe United States is cost-ineffective because ofthe cost of energy (in the form of natural gas)for the process. Producer costs have been cal-culated as $160/ton (61) whereas the sellingprice is in the range of $85 to $105/ton. Thus,biological nitrogen fixation through the use oflegumes may be resorted to increasingly, notonly to reduce the cost of on-farm inputs, butalso to save foreign exchange and avoid over-dependence on foreign powers.

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But economic pressure alone will not guar-antee adoption of BNF-based technology with-out compelling demonstration of greater ben-efits from BNF by legumes. The dramaticincrease in interest in BNF since the energycrises of 1973, 1974, and 1979 has brought itunder the scrutiny of agencies and individualswhose concern is its viability as a productiveagricultural technology now rather than itsoften acclaimed potentials for the future.

The agricultural research community needsto undertake a comprehensive program of tech-nology development where the relative distri-bution of funding and manpower investmentis realistically prioritized. Research to stabilizegrain legume yields can increase the contribu-tion of biological nitrogen fixation in tropicalfarming systems more than much of the re-search on the BNF process per se in grain leg-umes. Similarly, research to select forage leg-ume germplasm that is adapted to the soils andclimates of the world’s underused savannahs,and development of appropriate legume-basedpasture management technology, can be ex-pected to increase the use of biological nitro-gen fixation even without further research onthe BNF process. These statements assume thateffective modulation can be guaranteed. Sincethis is not always the case, those specific as-pects of BNF research that study the factorsthat limit modulation and nitrogen fixation intropical soils should be given highest priority.

CONSTRAINTS ON IMPLEMENTATION OF BNF TECHNOLOGY

There are still many unknowns in the scien- ulant technology have been known for manytific understanding of BNF, and research into years and have already made major contribu-the biochemistry and genetics of the process tions to agricultural production—initially inis particularly intense and competitive. B u t Australia and, more recently, worldwide asfew, if any, of these unknowns are really con- soybean cultivation has been increasing. Thestraining the implementation of legume-based real constraints to fuller implementation ofBNF technology. The basic principles of inoc- BNF technology relate to delivery of the tech-

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nology, both to potential inoculant producersand to farmers, and acceptability of the tech-nology.

There has not been adequate demonstration,under realistic conditions in the developingcountries, of the yield increases and/or reducedfertilizer needs that are repeatedly stated to bethe benefits of BNF technology. In some cases,inoculation trials have been performed and noresponse obtained. But these trials have beenmainly with imported inoculants, the qualityof which at the time of their use was not orcould not be verified. Thus, a related constraintis the lack of trained personnel with the essen-tial combination of agronomic and microbio-logical skills for executing production-orientedresearch on BNF technology.

Research is necessary to adapt BNF technol-ogy and develop appropriate Rhizobium strainsand inoculation procedures for use in the Trop-ics and Subtropics. Current inoculation tech-nology as used in the United States and Aus-tralia is suited to legumes grown under favor-able conditions with relatively high comple-mentary agronomic inputs. Transferability ofthis technology to situations where the legumesare grown under marginal conditions withminimal inputs, and confronted with one ormore soil and climatic stresses, is in somedoubt (37).

It is the genotype of the legume that is to beinoculated that is the prime determinant of thestrain used in rhizobial inoculants, rather thanthe characteristics of the soil where the inoc-ulant will be introduced. This is contrary towhat is expected by many first-time users.

For example, in providing inoculant servicesin Latin America and Hawaii, it has been com-mon to receive data from soil analysis togetherwith requests for inoculants. Farmers expectthe selection of legume inoculant to be madeafter consideration of local soil and climate,just as would be the choice of crop variety. Yetthere are few instances in which an inoculantstrain is recommended in commercial produc-tion because of the soil characteristics. Rhizo-bium strain CB 81 is recommended for Leu-

caena leucocephala sown in acid soil and NGR8 for alkaline soils (48).

When soil characteristics are very different,the response to inoculation and the relative per-formance of rhizobial strains is also different.Even apparently similar soils can show differ-ent performances. Thus some authors advocatethat simple “need-to-inoculate” trials alwaysbe performed at the local level due to the un-predictability of the response to inoculation(11,22,23). This suggestion would result in leg-ume inoculation being tested, essentially bytrial-and-error, at every site where legumes areto be grown. Inoculation technology needs tobe more transferable than this, otherwise itsvalue as an agrotechnology is questionable.

There are significant differences betweensites in the size of their indigenous rhizobialpopulations (42,55) and in the range of strainsof Rhizobium in the indigenous microflora(43,55). Such differences have been attributedto the effect of soil factors (43,5) though the pos-sibility of widespread correlations betweenspecific soil characteristics and rhizobial oc-currence in tropical soils has not been criticallyexamined.

The response by tropical legumes to inocu-lation with rhizobia also varies from site to site(11,22,34,35,44,16). Such variation has been at-tributed to: differences in number, effective-ness, and competitiveness of native strains (40,27,55,38); variation in quality of the inoculantat its time of use (14); and variation in soil ni-trate levels (57). The possibility that the re-sponse to inoculation could be predicted on thebasis of a more thorough description of soil andenvironmental characteristics has not beentested.

The relative performance of strains selectedunder optimal conditions for a specific legumeis variable, depending on the site where theyare introduced (16). With inoculants that con-tain a mixture of strains of Rhizobium, it iscommon for one strain to dominate in the re-sulting nodule population (33,39). The possi-bility that rhizobial strains might be selectedfor adaptation to particular soil and environ-

mental conditions is not now exploited in trop-ical agriculture.

A serious constraint to fuller implementationof BNF technology is the lack of domesticallyproduced, high-quality inoculants in the Trop-ics and Subtropics, Thus, factors which detergovernment organizations or private enterprisefrom undertaking inoculant production in aparticular country are also constraining BNFtechnology. Among these are: high capital costof inoculant production plant (of the type usedin the United States and mistakenly assumedto be needed in any production plant); highoperational cost associated with retaining aprofessional and well-trained staff to run theplant; operational risks associated with lossesdue to such factors as contamination; absencein most developing countries of an adequateinfrastructure that would permit marketingand distributing a biological product with no-torious vulnerability to high temperatures;reticence to embark on an enterprise in ad-vance of official control standards being estab-lished (compounded by official reticence to setstandards until there is an industry to be con-trolled); and insufficient demand and uncer-tain future demand for inoculants.

The present nature of BNF technology meetsconsiderable farmer resistance, i.e., the coatingof seeds with peat inoculant. In Brazil, packetsof inoculant are included “free” by some seeddistributors with all seed sales. However, theinoculant is frequently discarded by farmersnot only because of the nuisance associatedwith its use, but also in part because of an un-fortunate impression that if inoculant is “free”it is of little value.

The cost of inoculants is not usually a con-straint to farmers who outlay capital for seed.Inoculant will seldom exceed 1 percent of theseed cost. For subsistence farmers who do notordinarily purchase seed, the capital outlay forinoculant, albeit small, may be a disincentive.Cost becomes a more important considerationwith granular forms of inoculant because therate of application is much greater than withseed-applied inoculant.

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BNF technology is a difficult technology todeliver by normal extension mechanisms.Thus, a lack of illustrative pamphlets and otheraids both for extension agents and the farmersis also a constraint on implementation of BNFtechnology at the farm level.

Furthermore, few of the senior administra-tors and decisionmakers who determine agri-cultural policy in the developing countries arefully aware of the applications for legume-based BNF technology. Most policy makers areaware of some of the attributes of legumes,Relatively few appreciate the role played bybiological nitrogen fixation, and among thosean even smaller number recognizes that it maybe essential to employ specific technologies toensure that maximum nitrogen fixation occurs.Thus, there is a need for educational material,specifically developed for decisionmakers,bringing to their attention the need to adaptavailable technology to the particular circum-stances where it is to be employed.

As BNF technology is being implemented,new constraints are emerging that are best de-scribed as “scientific” and are researchable.For example, some countries do not have peatdeposits suitable for carrier materials for in-oculant production and alternate materialsmust be identified and validated. Also, specificsoil and climatological stresses such as extremesoil acidity and the associated high levels oftoxic elements like aluminum and manganesemay require selection of strains of rhizobia tol-erant to those conditions.

The large number of competent researcherswho expend their energies and resources re-searching aspects of BNF other than limitingfactors such as the examples cited above is alsoa constraint on fuller implementation of BNFtechnology. Funding agencies do not alwaysrecognize a distinction between applied andless practical research in the area of biologi-cal nitrogen fixation. Biological nitrogen fixa-tion has great pertinence to agriculture produc-tion in developing countries, but not all re-search conducted under the BNF umbrella isapplicable in agriculture.

176

SCENARIO FOR FULL IMPLEMENTATION ON BNF TECHNOLOGY

The constraints on fuller implementation ofBNF technology are not solely scientific, butinclude cultural, socio-economic, and politicalfactors. Thus, the scenario where BNF mightrealize its potential would necessarily be multi-faceted and comprehensive.

The current trend toward energy-efficientfarming systems to reduce capital outlay forimported fertilizers can be expected to contin-ue and intensify. Manufacture of nitrogen fer-tilizers requires high energy consumption, sotheir price and availability is influenced in-creasingly by oil-rich nations. There is addedattractiveness in alternate nitrogen sources toavoid further dependence on foreign powers.Legume-based BNF technology is the major op-tion available and is likely to be resorted tomore and more.

The use of legumes and appropriate inocu-lant technology has the potential to increasethe amount of biologically fixed nitrogen enter-ing agricultural production systems. Given thatthe main value of legumes is their high-proteingrain, rather than their nitrogen contributionto nonleguminous food crops such as cerealsand root crops, the scenario for full realizationof BNF technology’s potential would need toinclude a swing in consumer preferences awayfrom crops that depend so heavily on nitrogenfertilizer. Thus, in the gambit of BNF researchpriorities, attention will need to be given tolearning the cultural and scientific bases forthese preferences and to alleviating the con-straints to greater consumer acceptance oflegumes.

The major increases in benefits from legume-based BNF technology will arise through an in-crease in the total acreage in legume produc-tion; innovative use of legumes in roles theyhave not previously occupied; and by ensur-ing that biological nitrogen fixation in legumesis maximum through appropriate inoculationtechnology. Much remains to be done to im-prove the role now played by biological nitro-gen fixation components. There is a wide dis-crepancy between farmers’ yields and the

known yield potential of grain legumes. Fur-thermore, it is disconcerting that in the major-ity of legume trials that include nitrogen fer-tilizer application, the legumes responded tonitrogen fertilization. This is disconcerting be-cause it means that even when legumes weregrown under favorable management in exper-iments, let alone in farmers’ fields, the symbi-otic association of the legume with rhizobiumwas defective. Therefore, the potential to dou-ble or triple the nitrogen benefits described inthis report exists through development of tech-nology that would assure establishment of max-imally effective rhizobial symbioses in tropi-cal legumes under tropical conditions.

Greatest future potential would appear to restin developing:

●

●

●

●

●

legume-based pastures and viable multiple-cropping systems including legumes forunderused savannahs;agroforestry systems that combine fast-growing, nitrogen-fixing trees, legumes,and other crops to meet the food and fuelrequirements of the rural poor;fast-growing leguminous trees for reforest-ing water catchment areas following for-est clearance;legume-based cropping systems to givesustained productivity in tropical soils fol-lowing jungle clearance; andselection of deep-rooted, drought-tolerantleguminous trees that can serve as browsespecies in the world’s dry lands.

Reference has already been made to the needto exploit fully the variation in host plant,rhizobial strain, and environment interactionwhen selecting the optimal BNF package foreach circumstance. Legume programs shouldretain the services of a professional microbiol-ogist, but this suggestion is not practical. First,few legume programs can afford the luxury ofa full-time microbiology position and second,there is a worldwide shortage of professionalsoil microbiologists that is unlikely to bealleviated significantly for about 10 years. Theworld’s major multidisciplinary legume pro-

177

grams should, however, have their own micro-biologists. This is already the case with theIARC programs for beans, cowpeas, pigeonpeas, groundnuts, chickpea, and tropical for-ages. INTSOY, working with soybean, has itsown soil microbiologist. Also, there are severalnational legume programs where microbiolog-ical support is integrated through a participat-ing institute with expertise in the BNF area(e.g., Brazil, India).

The needs of the other legume programs forBNF expertise could be met through the pro-vision of one (or more) BNF Resource Center(s).Such centers could provide technical assis-tance, offer support services (germplasm andinformation), provide professional and techni-cal training, and conduct research necessaryto adapt BNF technology to specific local con-ditions when it is beyond the capability of localresearchers. Such centers would require a crit-ical mass of BNF researchers to be able to carryout a comprehensive support program and stillretain a capability to respond to technical assis-tance requests.

The BNF Resource Center(s) would best belocated at universities in developed countries,and preferably in the Tropics. A university sitewould help provide professional training, im-portant if national institutions in developingcountries are to be able to sustain their ownBNF programs. Short-term, non-degree train-ing programs in BNF technology should be of-fered to key personnel working on researchprograms involving the legume/rhizobium sym-biosis. This is more effective in the short termthan Ph.D. or M.S. programs which tend to bea passport out of research into better paid ad-ministrative positions for many graduates re-turning to their home country. The short coursesshould be offered in cooperation with devel-oping country institutes to generate a regionalcapability for offering such courses. Theyshould be complemented by on-the-job train-ing tailored to the needs of selected individualsthat would be conducted at the BNF ResourceCenter and include visits to pertinent indus-try facilities.

Such BNF Resource Centers would engageinformation specialists to develop communi-cations materials suitable for the many cli-entele groups. This would range from news-letters for administrators to pamphlets for ex-tension agents and include providing informa-tion for developing country researchers, whooften do not have access to libraries.

Agricultural research tends to focus man-power and resources on improvement of singlecommodities. Some organizations, like IARCs,are characterized by multidisciplinary teamswith specific crop and/or geographic man-dates. Establishing a BNF Resource Centerwould be considered by some as a return todiscipline-oriented research. This author con-tends that the key element in the success ofcommodity programs such as some of those inthe IARCs has been that they are highly fo-cused and actively managed in pursuit of well-defined research priorities rather than attribut-able to the commodity approach per se. A pro-gram investing manpower and financial re-sources in an actively managed BNF programthat is sharply focused on the constraints to fullimplementation can be expected to make realprogress. The specialized and sophisticated na-ture of rhizobium bacteriological expertise andthe scarcity of experienced manpower is fur-ther justification for assembling a critical massof rhizobiologists in a single BNF ResourceCenter.

An additional advantage in the existence ofsuch a BNF Resource Center would be a ca-pability to extend BNF technology developedat a particular place to other crops and regions.Staff of the BNF Resource Centers would travelas required and undertake short (1 to 3 months)or longer (3 months to 3 years) assignments insupport of specific outreach activities whenwarranted. Only travel would help the person-nel of the BNF Resource Centers focus theirattention on researchable constraints in realagricultural situations in the developing coun-tries. Additionally, the Resource Centers wouIdwork closely with other universities and re-search organizations where specific research

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on factors limiting BNF use could be referredunder subcontract.

The BNF Resource Center would need to de-velop links with commercial inoculant produc-ers to begin appropriate assistance programsfor government organizations or private enter-prise in developing countries contemplating in-oculant production. Such programs would cov-er not only technical aspects of the productionof inoculants but also the business aspects ofsmall enterprise production, marketing, anddistribution of inoculants. The BNF ResourceCenter should develop specifications, includingsources of all equipment items, for inoculantproduction facilities that would be feasible atlevels of capital investment ranging from$50,000 to as high as $1 million. The Centershould also advise governments on an appro-priate mechanism for quality control.

The Center would also need to develop stronglinks with major legume germplasm centersand those involved in legume improvement toencourage simultaneous exploitation of hostlegume and rhizobial germplasm in selectionsfor particular soils and climates.

The BNF Resource Center would take a ma-jor organizational responsibility for callingworkshops and scientific meetings to coordi-nate international experimentation and dissem-inate results.

The major activity to be undertaken by theBNF Resource Center would be the coordina-tion of competent, standardized experimentsdesigned to generate the data necessary toquantify the economic yield benefit attributableto legume inoculation under field conditions.Such trials would also serve as local demon-strations of the benefits from legume inocu-lation.

The core budget for such a BNF ResourceCenter should be guaranteed by the host gov-ernment through its agency responsible for in-ternational development. The host institution(university) cannot realistically be expected toprovide direct financial support for such a Cen-ter given that the Center staff will not have con-

ventional instructional responsibility and thatthe research will aid mainly foreign nationswith only minor benefits for agriculture wherethe Center is located. The mandate of a BNFResource Center is international and therefore,the support should be international.

There is understandable reticence on the partof international funding agencies to expend re-sources in a center located in a developedcountry. The author contends that it is in thebest interests of the developing countries thatBNF programs be conducted by a Center lo-cated in the Tropics but sited in a developedcountry where it can receive unimpeded logis-tic support for its sophisticated operations andenjoy continuity of service from high calibreprofessional staff. Such a Center would be ul-timately more cost effective than fragmentedsupport to a myriad of in-country programs,an approach that often causes wasteful duplica-tion of effort. Furthermore, support of a BNFResource Center, for example in the UnitedStates with funding by USAID, would be pru-dent use of public funds. A large share of thebudget would be expended in the United Statessustaining employment of U.S. residents andstrengthening a U.S. institution without lessen-ing the support for the developing countries.Additionally, a greater degree of control couldbe exercised over the activities of a U.S.-basedCenter than is possible with grants to foreigninstitutions.

Agencies that could be anticipated to contrib-ute to a BNF Resource Center would be: FAO,UNEP, UNESCO, and UNDP. Technical assis-tance on a continuing basis to any specificcountry ought to be funded externally as aspecial project with funding arranged by thatcountry from its national budget and interna-tional development assistance grants or loans.

As a hypothetical estimate, the author sug-gests the following distribution of $10 milliontoward the implementation of legume-basedBNF technology (table 1). It is assumed that the$10 million is additional to current support forBNF.

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Table 1 .—Allocating Funds for a BNF Resource Center(How to Spend $10 million on BNF)

Salaries (6 professional and 12 subprofessionals)African network of trials/demonstrationsAmerican network of trtals/demonstrationsAsian network of trials/demonstrationsTraining programs in technologyProfessional (M.S., Ph.D.) trainingInformation servicesGermplasm servicesWorkshops/conferences (3 regional, 1 global)Research

Simplification of inoculant productionInnovative inoculation methods , . .Stress tolerance in inoculant strainsQuant i fy ing N f ixat ion/cyc l ing in cropping

s y s t e m s i n t h e t r o p i c sAdvisory servicesContingency fundI n d i r e c t c o s t s

BNF Resource Centersub-total

$3,000,000200,000200,000200000500,000150,000120,000100,000270.000

90,00090,000150,000

220,000200,00060,000

1,350,000

$7,000,000’Pilot Inoculant Plants

Zambia (year one) 250,600Ivory Coast (year one) 100,000Others (beginning third year) 1,000,000

Nitrogen-Fixing Tree Research (initially inHaiti/Thailand/Senegal). 500,000

Socio-economic Evaluation of BNF Technology 250,000Outreach Programs of BNF Resource Center

(beginning year 3)Z a m b i a 300,000B a n g k o k 300,000Peru 300,000

GRAND TOTAL $10,000,000%This figure is low for the level of operations envisioned and IS possible because a center withappropriate equipment and buildings has already been established and IS operating in the pro-posed BNF Resource Center mode (I. e. University of Hawaii NifTAL Project)

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69. Souto, S. M,, et al., “Espicificidade de umavariedade nativa de ‘alfalfa de Nordeste’ (Stylo-santhes gracilis H. B. K,) na simbiose com Rhi-zobium sp,, ” Proceedings V RELAR (Brazil,1970), pp. 78-91.

70, Thompson, J. A., “Application of Legume SeedInoculants,” (New York: Wiley-Chichester,1980), p. 489.

71. Vincent, J. M., “Environmental Factors in theFixation of Nitrogen by the Legume,” Soil Ni-trogen, ASA, 1965, pp. 384-435.

72. Vincent, J. M., “A Manual for the PracticalStudy of the Root-nodule Bacteria, ” IBP Hand-book No, 15, 1970.

73. Virtanen, A. I., and Laine, T., “The ExcretionProducts of Root Nodules and Mechanism ofN-Fixation, ” Biochem. J. 33:412-427, 1939.

74. Virtanen, A. I., and Linkola, H., Nature 158:515,1946.

75. Virtanen, A. I., Biol. Revs. L’ambridge Phil. Soc.22:239-269, 1947.

76, Walker, T. W., et al., “The Nitrogen Economyof Grass Legume Associations, ” J. Brit. GrassId.SOC. 9:249-274, 1954,

77. Weber, D. F., et al,, “Some USDA Studies onthe Soybean-Rhizobium Symbiosis, ” Plant andsoil, special volume, 1971, pp. 293-304.

78. Wetselaar, R,, and Hutton, J. T., “Ionic Com-position of Rain Water at Katherine, N. T. andIts Part in the Cycling of Plant Nutrients,” Aust,J. Agric. Res. 14:319-329, 1963.

79. Williams, W., “White Clover in British Agricul-ture, ” Brit. GrassId. Soc. Occ. Symp. 6, 1970,pp. 1-1o.

80, Wilson, P, W,, and Burton, J. C,, J. Agric. Sci.28:307, 1938,

81. Wyss, O., and Wilson, P. W,, Soil Sci. 52:15-29,1941.

182

Acronyms

ARC —Agricultural Research CenterBNF —Biological Nitrogen FixationBTI —Boyce Thompson Institute (Cor-

nell University)CB 81 —CSIRO, Brisbane, Rhizobium

strain 81CGIAR —Consultative Group on Interna-

tional Agricultural ResearchCIAT —Centro International de Agricul-

tural Tropical (Colombia)CRSP —Cooperative Research Support

ProgramFAO -–-Food and Agriculture Organiza-

tion (of the United Nations)IARC(s) —International Agricultural Re-

search Center(s)IBIT —International Bean Inoculation

TrialIBPGR —International Board for Plant

Genetic ResourcesICARDA —International Center for Agricul-

tural Research in Dry Areas(Syria)

ICRISAT —International Crops Research In-stitute for the Semi-Arid Tropics(India)

IITA —International Institute for Tropi-cal Agriculture (Nigeria)

INLIT —International Network of Leg-ume Inoculation Trials

INTSOY —International Soybean Program(University of Illinois)

ISRIE —International Soybean Rhizobi-um Inoculation Experiment

MIRCEN—Microbiological Resources Cen-

NGR 8NifTAL

OTA

SEA/CR

UNDP

UNEP

ter (UNEP/UNESCO project)—New Guinea, Rhizobium strain 8—Nitrogen Fixation by Tropical

Agricultural Legumes (Universi-ty of Hawaii)

—Office of Technology Assess-ment (U.S. Congress)

—Science and Education Adminis-tration/Cooperative Research(USDA)

—United Nations DevelopmentProgram

—United Nations EnvironmentalProgram

UNESCO—United Nations Educational,Scientific, and Cultural Organi-zation

USAID —United States Agency for Inter-national Development

USDA —United States Department ofAgriculture

Chapter X

Mycorrhiza AgricultureTechnologies

John A. MengeAssociate Professor

Department of Plant PathologyUniversity of California

Riverside, CA 92521

Contents

Page

Introduction—What Are Mycorrhizal Fungi? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185Ectomycorrhizae . . . . . . . . . . . . . . . . . . . . ,,, .,, ,, . . . .,.,.,... . . . . . . . . . . . . . 185Vesicular-Arbuscular (VA) Mycorrhizae . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . 185

How Do Mycorrhizal Fungi Improve the Growth of Agricultural Plants? . . . . . . . . 187Mycorrhizae as Substitutes for Fertilizers . . . . . . . . . . . . . . . . . . . . . . . .,.,., ,..,,, 189Current Commercial Use of Mycorrhizal Fungi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

Disturbed Sites ..............,,. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191Fumigated or Chemically Treated Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191Greenhouses .. .,..., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .....,.,., . . . . . . . . . . 192

Commercial Production and Inoculation With Mycorrhizal Fungi . . . . . . . . . . . . . . 192Potential Uses of Mycorrhizal Fungi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195Constraints on the Commercial Use of Mycorrhizal Fungi . . . . . . . . . . . . . . . . . . . . . 197Effects of Mycorrhizal Fungi on Agriculture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198Conclusions and Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

Table

Table No. Page

1. Estimated Cost of production of Vesicular-Arbuscular Mycorrhizal Inoculum onSudangrass in 4 Inch Pots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

Figures

Figure No. Page

l. Diagram of a Typical Ectomycorrhiza Including the Hartig Net, Fungal Mantle,and External Hyphae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

2. Diagram of a Typical Vesicular-Arbuscular Mycorrhiza Including Vesicles,Arbuscules, Spores, and External Hyphae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

3. The Growth of Citrus Seedlings With and Without VA Mycorrhizal Fungi andat Different Nutrient Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,. . . . . . , 188

4. Dry Weights of Mycorrhizal and Non-Mycorrhizal Brazilian Sour Orange andTroyer Citrange Seedlings Fertilized With Different Amounts of Phosphorus., . 190

5. Proposed Scheme for the Commercial Production of Vesicular-ArbuscularMycorrhizal Inoculum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

Chapter X

Mycorrhiza Agriculture Technologies

INTRODUCTION-WHAT ARE MYCORRHIZAL FUNGI?

Mycorrhizal fungi are beneficial fungi thatare associated with plant roots via a symbioticassociation whereby both the host plant andthe fungus benefit. Mycorrhizae are the struc-tures formed by the symbiotic association be-tween plant roots and mycorrhizal fungi. My-corrhizae contain both plant roots and fungaltissues. In nature, mycorrhizae are far morecommon than non-mycorrhizal roots (24,92,94).Nearly all plant species are associated with my-corrhizal symbionts. Because of their impor-tance to plants and their widespread distribu-tion, mycorrhizae must be considered in allaspects of plant ecology, crop science, and agri-culture.

Mycorrhizal fungi are divided into four verydifferent types (66): ectomycorrhiza, vesicular-arbuscular mycorrhiza (abbreviated as VA my-corrhiza), ericaceous mycorrhiza, and or-chidaceous mycorrhiza. As indicated by theirnames, ericaceous mycorrhiza and orchida-ceous mycorrhiza are associated with erica-ceous plants (blueberries, cranberries, azaleas,etc.) and orchidaceous plants (orchids), respec-tively. Because of the relatively low economicimpact of these plants and the small amountof available data on these types of mycorrhiza,they will not be discussed further.

Ectomycorrhizae

Ectomycorrhizae are associated primarilywith trees such as pine, hemlock, spruce, fir,oak, birch, beech, eucalyptus, willow, and pop-lar, Ectomycorrhizae are formed by hundredsof different fungal species belonging to theBasidiomycetes (mushrooms and puffballs) andAscomycetes (cup fungi and truffles). Thesefungal symbionts are stimulated by root ex-udates and grow over the surface of host feederroots to form a thick fungal layer known as afungal mantle (figure 1). Hyphae of ectomycor-

Figure 1 .—Diagram of a Typical EctomycorrhizaIncluding the Hartig Net, Fungal Mantle, and

External Hyphae (courtesy D. H. Marx)

rhizal fungi penetrate between the cells of thehost root, develop around the root corticalcells, replace the host middle lamella, and formwhat is called the “Hartig net’’—the distin-guishing feature of ectomycorrhizae. In re-sponse to the fungal invasion, the host rootsusually swell substantially and may branch di-chotomously or in a coralloid manner. The rootcells are not injured, however, and function ofthe roots is enhanced, as we shall discuss.

Vesicular-Arbuscular (VA)Mycorrhizae

VA mycorrhizal fungi have the widest hostrange and form by far the most common typeof mycorrhizae. VA mycorrhizae occur onliverworts, mosses, ferns, some conifers, andmost broad-leaved plants. Only 14 families thatare considered primarily non-mycorrhizal (28).The important crop families that are non-my-corrhizal are Cruciferae (cabbage, broccoli,mustard, etc.); Chenopodiaceae (spinach, beet,

185

— —

186

etc.); Cyperaceae (sedges); and Caryophyllaceae(carnation, pinks, etc.). wetland rice also is usu-ally non-my corrhizal. Nearly all other impor-tant agronomic crops including wheat,potatoes, beans, corn, alfalfa, grapes, datepalms, sugar cane, cassava, and dryland riceare associated with VA mycorrhizal fungi. Al-though many trees have ectomycorrhizae, mosthave VA mycorrhizae. Sixty-three of sixty-sixtropical trees in Nigeria (77) are associated withVA mycorrhizae. So are most important treecrops such as cocoa, coffee, rubber, and cit-rus. Some trees such as juniper, apple, and pop-lar can have either ectomycorrhizae or VAmycorrhizae.

The fungi that form VA mycorrhizae, about80 species, are in a few genera in the Zygomy-cetes class of fungi. They are so common insoils that literally any field soil sample fromarctic to tropical regions will contain thesefungi (66).

The hyphae of VA mycorrhizal fungi pene-trate directly into the root cortical cells of hostplants. Inside of the host plant cells, VA mycor-rhizal fungi form minute coralloid structuresknown as arbuscules (figure 2). Arbuscules arethought to be the site of nutrient transfer be-tween the symbiotic partners. The host plantsobtain fertilizer nutrients from the mycorrhizalfungus while the fungus obtains sugars or otherfood materials from the plant. Although the ar-buscule of VA mycorrhizal fungi occurs insideroot cells, they remain covered by the host cellmembrane and so are not in direct contact withthe host cytoplasm. Vesicles are balloon-likemycorrhizal fungus structures that usuallyform inside the host root. These structures arethought to be storage organs that the fungusproduces to store nutrient materials inside ofthe plant host.

VA fungi also produce abundant spores ei-ther inside or outside of host roots. These

Figure 2.—Diagram of a Typical Vesicular-Arbuscular Mycorrhiza Including Vesicles, Arbuscules,Spores, and External Hyphae

187

spores are the survival structures of VA mycor-rhizal fungi. They are long-lived and extremelyresistant to most unfavorable soil conditions.These spores are responsible for the wide-spread occurrence of VA mycorrhizal fungi innearly all soils throughout the world. Despitethe intracellular penetration by VA mycorrhi-zal fungi, they do not affect the roots’ outwardappearance except by inducing a yellow col-oration in some hosts (4). Detection of VA my-corrhizal roots is best done by staining rootsand examining them microscopically for thepresence of hyphae, arbuscules, or vesicles (73).

Arbuscules of VA mycorrhizal fungi areshort-lived and generally survive for less than

2 weeks before they are digested by the hostplant (61,90). Plant roots normally release largequantities of chemical “exudates” into the rootzone (8). Since the arbuscules are covered bythe host membrane it is thought that the sym-biotic association is regulated by the host plantvia the cell membrane. The more nutrient ma-terials released by the plant membrane to thearbuscule of the mycorrhizal fungus, the moreabundant the mycorrhizal colonization (76). Byrestricting nutrients passing through the plantmembrane the plant is capable of restrictingmycorrhizal infection in roots. A similar mech-anism can be postulated for the regulation ofectomycorrhizae by plant roots.

HOW DO MYCORRHIZAL FUNGI IMPROVE GROWTH OFAGRICULTURAL PLANTS?

The VA mychorrhizal symbiosis results i nmarked increase in crop growth and develop-ment. For example, inoculation of fumigatedsand or soil with VA mycorrhizal fungi will in-crease the growth of citrus by as much as 1600percent (figure 3); (42), grapes by 4,900 percent(74), soybeans by 122 percent (84), pine by 323percent (100), and peaches by 80 percent (44).Growth responses due to VA mycorrhizal fungihave been observed in cotton (82), tomatoes(16), corn (27), wheat (41), clover (75), barley(5), potatoes (7), ornamental plants (99), and inmany other crops.

VA mycorrhizal fungi stimulate plant absorp-tion of phosphorus (85,74,28,62), zinc (44,61),calcium (84), copper (84,85,60,42), iron (60),magnesium (36,61), and manganese (84,61). In-creased uptake of phosphorus is perhaps themost important benefit provided by mycorrhi-zal fungi,

Most researchers agree that the increase ineffective nutrient absorbing surface providedby mycorrhizal fungi is primarily responsiblefor the increase in uptake of soil nutrients bymycorrhizal plants. Hyphae from figure 3 my-corrhizal plant roots can extend up to 8 cm intothe surrounding soil and transport nutrientsthis distance back to the roots (83).

VA mycorrhizal fungi may increase the ef-fective absorbing surface of a host root by asmuch as 10 times (6). Nutrient ions such asphosphorus, zinc, and copper do not diffusereadily through soil. Because of this poor dif-fusion, roots deplete these immobile soil nu-trients from a zone immediately surroundingthe root. Mycorrhizal hyphae extend into thesoil past the zone of nutrient depletion and canincrease the effectiveness of absorption of im-mobile elements by as much as 60 times (6).Others have calculated that approximately 50cm of mycorrhizal hyphae per cm root is nec-essary to account for the uptake of phosphorusby mycorrhizal plants (89), Experimental obser-vations indicate that plant roots can have morethan 80 cm of mycorrhizal hyphae, more thanthe amount necessary to account for the ob-served phosphorus uptake,

Plant uptake of mobile soil nutrients such asnitrogen and potassium is rarely improved bymycorrhizal fungi, Normal soil diffusion is ade-quate to supply roots of plants with these nu-trients whether the roots have a large absorb-ing surface or not. Generally, plants that aremost dependent on mycorrhizal fungi for nu-trient uptake are those having roots with a lowsurface to volume ratio; that is, plants withcoarse, fleshy roots with few root hairs (2).

38-846 0 - 85 - 7

188

Although some scientists speculate that my-corrhizal fungi can solubilize and absorb nu-trients that are unavailable to plant roots, thereis little evidence to support this claim. Sandersand Tinker (88) showed conclusively with 32p-labelled phosphate that mycorrhizal fungi usethe same phosphorus sources as do plant rootsbut they are able to absorb from a larger soilvolume and so are responsible for the vast ma-jority of phosphorus absorption by crop plants.

Mycorrhizal fungi can also enhance watertransport in plants (87) and prevent water stressunder some conditions (54). This probably isnot a direct effect of mycorrhizal fungi, but in-stead is because of the improved nutrient statusprovided by the mycorrhizal fungi. Mycorrhi-zal fungi can endure much dryer soil condi-tions than can most plants and it is thought thatplants may benefit from mycorrhizal infection

under drought or water-stressed conditions(66,86). Ectomycorrhizae, in particular, withtheir mantle surrounding the roots, may pro-vide a physical barrier against root dessication.

Considerable evidence exists to suggest thatmycorrhizal plants may be better equipped towithstand the toxic effects of salt. Calcium,magnesium, and sodium concentrations innon-mycorrhizal citrus were 41 percent, 36 per-cent, and 150 percent greater than in mycor-rhizal citrus (55). Hirrel and Gerdemann (35)found that mycorrhizal fungus increased bellpeppers tolerance to salinity. Trappe, et al. (98),indicated that VA mycorrhizal fungi providedresistance to the toxic effects of arsenic. My-corrhizae may also provide tolerance to ex-cessive soil manganese and aluminum (34).

Mycorrhizal fungi also act to increase modu-lation by symbiotic nitrogen-fixing bacteria

189

such as Rhizobium (64,69). Mycorrhizal fungimay stimulate other beneficial rhizosphere or-ganisms as well (1)0

Ectomycorrhizal fungi have been reported toprovide resistance to plant disease in manyplants (48). Although mycorrhizae never con-fer complete immunity, they often appear toreduce the severity of disease or symptom ex-pression. Resistance of ectomycorrhizae to dis-ease may result from (48):

● mechanical protection by the mantle,● better plant nutrition,Q production of antibiotics by the mycorrhi-

zal fungus,● competition for infection sites,● formation of phytoalexins, and● alteration of root exudates.

Evidence is accumulating that VA mycorrhi-zal fungi exert similar effects on plant patho-gens. Schenck, et al, (91), has reported mycor-rhizal resistance to root-knot nematodes.Schonbeck (93) has examined a variety of foliarand root pathogens on mycorrhizal plants andconcluded that root pathogens (Thielaviopsis,

Fusarium, nematodes, etc.) are usually inhib-ited by mycorrhizal fungi while foliar patho-gens (viruses, rusts, etc.) are often more severeon mycorrhizal plants. Davis, et al. (21,22), andDavis and Menge (20) concluded that the VAmycorrhizal fungus Glomus fasciculatus pro-duced little resistance to Phytophthora root rotin citrus and indeed increased Phytophthoraroot rot in avocado and Verticillium wilt in cot-ton. VA mycorrhizal effects on disease may re-sult from improved phosphorus nutrition be-cause of the increased absorbing surface of themycorrhizal hyphae. This effect is magnifiedwhen the roots’ normal absorbing capacity isreduced because the roots are partiallydecayed.

There have been reports of mycorrhizal fungiactually reducing growth of some plants (11,39,13). These parasitic effects are rare and thereason for them is not understood, but they ap-parently occur in grasses, cereals, andtomatoes at or above optimum soil nutrientlevels when the plant is actively regulatingmycorrhizal invasion,

MYCORRHIZAE AS SUBSTITUTES FOR FERTILIZERS

In the past 40 years the use of agriculturalfertilizers has more than doubled. Crop yieldshave risen dramatically as a result. However,because of shortages in some fertilizer suppliesand the high cost of energy, the cost of fertil-izers has risen tremendously. Agriculturaleconomists indicate that as energy costs risethe most responsive agricultural input is fer-tilizer. That is, as energy costs rise, fertilizeruse will decrease. This response is a dangerousone since chemical fertilizers are said to ac-count for one-third to one-half of the currentU.S. agricultural output (47).

Estimates indicate that agriculture uses be-tween 2.6 and 4.4 percent of all U.S. energyuse. Fertilizers and their application comprise30 to 45 percent of the total agricultural energyuse. Nitrogen is the main energy user, with

phosphorus and potassium accounting for only16 percent of the fertilizer energy use (47).

Because mycorrhizal fungi increase the effi-ciency of fertilizer use, they can be thought ofas “biotic fertilizers” and can indeed be sub-stituted for substantial amounts of some fer-tilizers (53,55). Mosse (61) maintains that 75percent of all phosphorus applied to crops isnot used during the first year and reverts toforms unavailable to plants. In soils high in pH,aluminum, or calcium carbonate, nearly 100percent of the phosphorus fertilizer can be im-mobilized to nonusable forms via chemical re-actions in the soil. Tropical oxisols and ultisolsare notorious for their capacity to immobilizephosphorus. Because mycorrhizal plants arebetter suited to exploiting soil with low amountsof available phosphorus, zinc, and copper, the

190

addition of large amounts of these fertilizerseach year may be unnecessary. Menge, et al.(55), compared mycorrhizal citrus seedlingswith non-my corrhizal seedlings that receivedvarious amounts of phosphorus fertilizer (fig-ure 4).

Mycorrhizal Troyer citrange that received nofertilizer phosphorus were equal in size to non-mycorrhizal Troyer citrange that received 112kg phosphorus per hectare, Similarly, mycor-rhizal Brazilian sour orange that received nofertilizer phosphorus were equal in size to non-mycorrhizal plants that received 560 kg phos-phorus per hectare. Concentrations of phos-phorus in non-mycorrhizal Brazilian sourorange leaf tissue were never above 0.05 per-cent (less than 0.9 percent phosphorus in-dicates phosphorus deficiency) even whenseedlings were fertilized with 1,120 kg

Figure 4.—Dry Weights of Mycorrhizal andNon-Mycorrhizal Brazilian Sour Orange andTroyer Citrange Seedlings Fertilized With

Different Amounts of Phosphorus

phosphorus per hectare. Concentrations ofphosphorus in leaves of mycorrhizal Braziliansour orange were above deficiency levels in allseedlings fertilized with more than 56 kgphosphorus per hectare. Concentration ofphosphorus in leaves of mycorrhizal Troyercitrange were never in the deficiency rangeeven when plants were not fertilized withphosphorus.

Non-mycorrhizal Troyer citrange, on theother hand, required over 56 kg phosphorus perhectare before adequate phosphorus concen-trations were restored to the leaves. At 1980retail costs for triple super-phosphate, it ap-pears that use of mycorrhizal fungi could re-sult in savings of $111 to $558/ha ($45 to$226/acre) in the cost of phosphorus fertiliza-tion of citrus in fumigated nursery soil. In oneCalifornia citrus nursery, it was found that in-oculation with mycorrhizal fungi could reducephosphorus fertilization by two-thirds and save$652/ha ($264/acre). Similar savings in phos-phorus fertilizers have been shown by Kor-manik, et al. (43), in fumigated forest nurseriesin the production of sweetgum.

Mycorrhizal fungi also can be substituted forcopper fertilizer in the culture of citrus seed-lings (97). Other data has shown that mycor-rhizal fungi can be substituted for zinc fertilizerin the greenhouse culture of citrus and evennitrogen fertilization can be reduced by asmuch as 300 percent in the presence of mycor-rhizae (Menge, et al., unpublished data). Thisnitrogen savings effect is probably due to anincreased efficiency of nitrogen use resultingfrom improved phosphorus nutrition of theplant.

Since mycorrhizal fungi are present in mostsoils, their unique fertilizer-absorbing abilitiesare normally already being used by most crops.If mycorrhizal fungi are removed or damagedin any way, then the amount of fertilizer re-quired by a crop increases enormously. Thisis demonstrated by reports that citrus grownin fumigated soil or in hydroponic solutionsoften require massive phosphorus applicationsfor adequate growth compared to field growncitrus (55). Citrus in the field can absorb phos-

191

phorus from phosphorus-deficient soils moreefficiently than either corn or tomatoes, andcitrus orchards do not normally require phos-phorus fertilization (9), Differences in phospho-rus absorption by citrus grown in fumigatedsoil and citrus grown in nonfumigated soils canbe reconciled if mycorrhizal fungi, which arepresent in nearly all citrus orchards (52), arethe equivalent of 100 to 500 pounds phosphorusper acre.

When and if the cost of fertilizer becomes ex-orbitant, we must devise the most efficient fer-tilizer supply systems possible—to minimizecosts while conserving energy and nonrenew-able resources. I submit that mycorrhizal fungicould be one alternative that might increasecrop yields and yet reduce fertilizer costs andenergy demands.

CURRENT COMMERCIAL USE OF MYCORRHIZAL FUNGI

Although nearly all plants require mycorrhi-zal fungi for maximum growth, the widespreadoccurrence of these fungi in nearly all soilslimits the immediate needs for inoculation withmycorrhizal fungi. Mycorrhizal fungi are cur-rently commercially usable in only three ma-jor agricultural areas: 1) disturbed sites, 2)fumigated soils, 3) greenhouses.

Disturbed Sites

Mycorrhizal fungi have been conclusivelyshown to improve revegetation of coal spoils,strip mines, waste areas, road sites, and otherdisturbed areas (18,19,15,49,81). In these stressedsites, mycorrhizal fungi are usually lacking andadding mycorrhizal fungi provides a nutrition-al advantage to associated plants in additionto providing possible resistance to low pH,heavy metal toxicants, and high temperature,

Fumigated or Chemically Treated Sites

Fumigation with biocides or pesticides suchas methyl bromide (56), chloropicrin (72),dazomet (50), 1,3-D (72), vapam (71), and vorlex(71) may destroy or inhibit root infection bymycorrhizal fungi, Application of many soilfungicides such as arasan (71), banzot (95),benomyl (96), botran (71), carbofuran (3),chloramformethane (37), dichlofluanid (37),ethirimol (37), lanstan (71), mylone (71), PCNB(96), sodium azide (3), thiabendazole (37),thiram (96), triademifon (37), tridemorph (37),and vitavax (96) have also been reported to be

harmful to mycorrhizal development, Flood-ing, planting non-my corrhizal crops, or remov-ing topsoil, may also reduce the population ofmycorrhizal fungi to a level requiring reinocu-lation (7,78).

Fumigation with the biocide methyl bromideto remove soil-borne pests is required by reg-ulation for the production of many nurserycrops. It is also regularly used in many fieldagricultural situations. This chemical is ex-tremely toxic to mycorrhizal fungi and mostfield fumigations are sufficient to destroy thenative mycorrhizal inoculum (56). Stunting ofcrops following fumigation with methyl bro-mide is common and is due to the destructionof mycorrhizal fungi. Although a relativelysmall amount of land is treated with this chem-ical, less than 100,000 acres annually in theUnited States, stunting following fumigationwith methyl bromide has been reported in theUnited States, Africa, Spain, Peru, Venezuela,and many other countries (52). Crops that areroutinely grown in methyl bromide fumigatedsoils include strawberries, tomatoes, tobacco,nursery crops, tree crop replants, and somevegetable crops. For many of these crops theaddition of mycorrhizal fungi following fumi-gation with methyl bromide is not only recom-mended but is imperative.

It appears that inoculating methyl bromidefumigated crops is economically possible. Thecost for inoculating nursery-grown citrus withmycorrhizal fungi is about $288/acre, while thecost for phosphorus fertilizer alone is $338/acre. Fumigated tomatoes receive $51 worth

192

of phosphorus per acre while the cost for my-corrhizal inoculation is less than $28/acre. My-corrhizal fungi can provide additional benefitsto the crop other than just improved phos-phorus nutrition.

For nursery plants grown in methyl bromidefumigated soil, inoculation with mycorrhizalfungi should be imperative for the followingreasons:

●

●

●

●

●

the plants grow better (prevents stuntingfollowing fumigation);there is a decreased need for fertilization,specifically phosphorus, zinc, and copper,resulting in decreased fertilizer cost andenergy conservation;there is decreased chance for water stressand therefore reduced transplant injury;mycorrhizal plants survive better especial-ly if transplanted to fumigated, poorly fer-tilized, or disturbed soil;plants will be inoculated with effective my-

●

corrhizal fungi rather than leaving mycor-rhizal infection to chance; andmycorrhizal plants may be more resistantor tolerant to some plant diseases.

Greenhouses

Greenhouse culture uses growth media suchas pine bark, vermiculite, perlite, builders sand,and peat moss and these are devoid of mycor-rhizal fungi. In addition, most greenhouseoperators steam, pasteurize, or chemically treattheir mixes to eradicate harmful pathogens.Nurserymen have compensated for the absenceof beneficial mycorrhizal fungi by applying lux-ury amounts of fertilizer and water to achievedesired growth. Inoculation of containergrown plants to reduce irrigation, fertilizer,and pesticide applications and cost can be doneas demonstrated by Chatfield, et al. (10), Lin-derman (46), and Crews, et al. (12).

COMMERCIAL PRODUCTION AND INOCULATION WITHMYCORRHIZAL FUNGI

Many ectomycorrhizal fungi can be readilycultured on artificial media and inoculum canbe grown under standard laboratory conditions(49). Experimentally, sterilized vermiculite andpeat moss is frequently saturated with a liquidnutrient medium (49) and is infested with a de-sirable ectomycorrhizal fungus. Ectomycorrhi-zal fungi generally grow quite slowly and maytake several months to colonize the vermiculite-peat moss mixture. This material can be usedon a small scale to inoculate nurseries andgreenhouses with mycorrhizal fungi. AbbottLaboratories, North Chicago, Illinois, has pro-duced massive amounts of inoculum of the ec-tomycorrhizal fungus Pisolithus tinctorius (86).Abbott Laboratories produced the peat moss-vermiculite-nutrient solution inoculum underlarge-scale commercial conditions using com-mercial fermenters.

Under the direction of D. H. Marx, the U.S.Forestry Service has undertaken a massivetesting program using the commercially pro-

duced inoculum. The inoculum will be testedin nearly 100 tree nursery test sites through-out the United States. Results will be availablewithin 4 years and will indicate the commer-cial feasibility of producing and using mycor-rhizal inoculum in fumigated tree nurseries.

Ectomycorrhizal inoculum can best be ap-plied in the nursery. Once the trees becomeinfected, the benefits can be transferred towherever the trees are grown. In the nursery,mycorrhizal inoculum can be distributed byhand and rototilled into the soil before plant-ing seed. Special machinery has already beenbuilt and is being used to incorporate ectomy-corrhizal inoculum.

Commercial production of mycorrhizal in-oculum for use in sterilized or fumigated soilis being attempted at several locations in theUnited States. Currently, the only way to pro-duce suitable quantities of a mycorrhizal in-oculum is on roots of susceptible host plants.

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The possibility of pathogenic organismscontaminating mycorrhizal inoculum is an ex-tremely serious problem when growing VAmycorrhizal inoculum in semi-sterile culturesin the greenhouse. For this reason, many scien-tists will consider mass production of VAmycorrhizal fungi only if it is done axenically(one organism only).

Realistically, however, not only must theseobligate parasites be grown in vitro, but theymust produce large quantities of spores inculture which will survive under soil condi-tions and infect plants in nature. Informationgained from the culture of other formerlyobligate parasites suggests that the possibilityof realizing this goal in the near future isunlikely. Even if mycorrhizal fungi are culturedaxenically, mycorrhizal inoculum for field use

will probably be produced on the roots of suit-able host plants.

With proper safeguards, mycorrhizal inocu-lum, free of plant pathogens, can be producedon plants in the greenhouse. Figure 5 illustratesa proposed scheme for producing mycorrhizalinoculum [53). VA mycorrhizal fungi can beisolated by using bits of roots or soil from thefield to inoculate roots of “trap plants” grow-ing in sterilized soil in the greenhouse. Sudan-grass (Sorghum vulgare Pers.) is frequentlyused, but other plants such as tomato, soybean,corn, and safflower may be equally suitable.The soil used throughout is a low nutrient sandfertilized once per week with one-half thestandard Hoagland’s solution minus phospho-rus. After production of VA mycorrhizal sporesin the “pot cultures,” the spores can be

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removed by wet sieving (29), elutriation (25),or centrifugation (85). These spores must besurface disinfested with substances such aschloroamine T or sodium hypochlorite andstreptomycin to assure that pathogens do notaccompany the spores (68).

These surface disinfested spores are used toinoculate the roots of plants that were ger-minated and grown under aseptic conditionsin growth chambers. The containers illustratedare made from plastic petri plates and filledwith the low nutrient sand. After 1 to 4 weeks

when the mycorrhizal fungi have infected rootsgrown under aseptic conditions root pieces canbe removed and stained (73) to observe infec-tion, root pieces are carefully removed andused to infect suitable host plants grown insterilized soil in the greenhouse. Similar rootpieces can be removed, examined, and platedon agar to observe pathogenic organisms.

If no pathogens are observed, the greenhouse“pot culture” may be used as a “mother cul-ture” to produce inoculum that will be used inthe field. Inoculum should be produced on se-lected hosts that have no root diseases in com-mon with the host plant for which the in-oculum is intended. For instance, inoculum forcitrus could be produced on sudangrass butnever on citrus. In this way the wide host rangeof most VA mycorrhizal fungi can be used. Asanother precaution against propagating path-ogens along with mycorrhizal inoculum, thefield inoculum should be drenched severaltimes with pesticides chosen to eliminate path-ogens known to infect the host for which theinoculum is intended. Mycorrhizal inoculumintended for citrus should be drenched witha nematicide to control the citrus nematodeand fungicides to control Phytophthora andRhizoctonia. Suggested pesticides are Ethazoleand PCNB. PCNB reduces the population ofmycorrhizal spores but the other pesticide canactually increase spore production (57). Severalother pesticides can be used without harmingmycorrhizal fungi (96).

Horticultural practices also could be used atthis point to maximize spore production. Elim-inating fertilization and slowly reducing the

water may be effective in increasing spore pro-duction. When spores are mature, plant topsare removed and roots, soil, and spores can beground up and partially dried (7 to 20 percentmoisture content) and stored at 40 C until used.If concentrated spore suspensions are desired,spores can be concentrated by wet sieving (38),elutriation (25), or centrifugation (85) beforestorage. VA mycorrhizal inoculum can befreeze-dried if desired (38). Inoculum producedin this manner should be consistently infectiveand yet pathogen free.

Using the method described above, the esti-mated costs for producing mycorrhizal in-oculum are shown in table 1. These figures arederived from production costs of a foliage plantgreenhouse and could be reduced considerably

Table 1 .—Estimated Cost of Production ofVesicular-Arbuscular Mycorrhizal Inoculum

on Sudangrass in 4 Inch Pots

Item Cost/pot1. Labor:

a. to prepare the soil mix . . . . . . . . . . . . . . . . . . $0.03b. potting, inoculating, and seeding. . . . . . . . . . 0.05c. moving pots to growing area . . . . . . . . . . . . . 0.03d. pruning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02e. spraying (insecticides and fungicides) . . . . . 0.03f. watering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02g. harvesting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.01h. grinding and packaging . . . . . . . . . . . . . . . . . . 0.03i. quality control . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02j. maintenance of mother cultures . . . . . . . . . . 0.05

Labor cost . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. Materials:

a. pots 4 ' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .b. seed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .c. fertilizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .d. shipping containers . . . . . . . . . . . . . . . . . . . . .e. insecticides and fungicides . . . . . . . . . . . . . .

Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3. Overhead expenses:

a. heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .b. depreciation on greenhouse . . . . . . . . . . . . . .c. depreciation on boilers . . . . . . . . . . . . . . . . . .d. maintenance allowance . . . . . . . . . . . . . . . . . .e. office supplies . . . . . . . . . . . . . . . . . . . . . . . . .f. management and office work . . . . . . . . . . . . .g. return on investment . . . . . . . . . . . . . . . . . . . .h. loss due to undeveloped plants . . . . . . . . . . .i. taxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .j. laboratory, incubator, etc. . . . . . . . . . . . . . . . .

$0.29

$0.070.0020.020.0250.03

$0.147

$0.080.0080.0030.0060.0020.030.010.0010.060.04

Total for overhead . . . . . . . . . . . . . . . . . . . . . . $0.24Total cost ... ... .$0.677Selling price ... ..$0.900.18¢/500 spores

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since mycorrhizal inoculum quality is of im-portance and not plant quality, A reasonablygenerous estimate of the cost of mycorrhizalproduction, including technical labor andquality control, together with a small marginof profit, indicates that consumers may payabout 0.180/500 spores of VA mycorrhizalfungi. Such a cost could reasonably be borneby consumers such as greenhouse operators ornurserymen.

A similar method to that outlined above hasbeen patented in England and is being per-fected for large-scale commercial use (34). Inthis method plants are grown in peat blocksthat are standing in a shallow nutrient-flowculture. After VA mycorrhizal spores are pro-duced in the peat blocks they are ground up,roots and all, for inoculation. The finishedproduct is not only excellent mycorrhizal in-oculum but is light and easy to ship.

Although many methods have been used toinoculate plants with VA mycorrhizal fungi ingreenhouse trials, few inoculation methods areacceptable for large-scale commercial inocu-lation. Several different methods to inoculatecorn have been studied and layering inoculumunder the seed was superior to seed inocula-tion or banding the inoculum (38), Hall (30) de-veloped a method for pelleting seed with a my-corrhizal infection and determined thatmycorrhizal fungi could survive up to 28 daysunder these conditions. Menge, et al. (53),found that layering inoculum below the seedand banding inoculum were superior to seedinoculations. Crush and Pattison (14) experi-mented with several means of inoculatingseeds with VA mycorrhizal fungi, but againfound that sowing seed above pelleted mychor-rhizal inoculum was the most effective methodfor obtaining mycorrhizal infection. Hattinghand Gerdemann (31) reported growth re-

sponses of citrus in a fumigated nursery afterinoculating citrus seed with mycorrhizal in-oculum. Gaunt (26) inoculated onion andtomato seeds with a VA mycorrhizal fungusand reported that seed inoculated plants grewas well as plants that were inoculated by mix-ing VA mycorrhizal inoculum into the soil.Commercial applications of mycorrhizal in-oculum using fertilizer banding machinerywere success fu l ly ca r r i ed ou t in c i t rusnurseries in California (23).

Commercial VA mycorrhizal inoculum isproduced using the method described above intwo citrus nurseries—Brokaw Nursery, SaticoyCalifornia and the Thermal Ranch, Thermal,California. Experimental VA mycorrhizal in-oculum is being produced and distributed ona large scale by Abbott Laboratories, North Chi-cago, Illinois. Other major corporations thatare supporting or carrying out research on VAmycorrhizal fungi include Dow Chemical Co.,Rohm & Haas Co., Dupont, Monsanto Co., andCeiba-Geigy Chemical Co.

Plants growing in all soils do not respond fa-vorably to VA mycorrhizal inoculum. If soil nu-trition is optimum, mycorrhizal fungi will notenhance growth of plants. A method for detect-ing which soils require mycorrhizae for max-imum production of citrus was devised byMenge, et al. (58). In soils with less than 34 ppmavailable P (Olson analysis), 12 ppm availableZn, 27 ppm available Mn, or 3 percent organicmatter, citrus trees will probably require my-corrhizal fungi for maximum growth. Mycor-rhizal inoculations are recommended only insoils with these characteristics, It is estimatedthat this includes approximately 85 percent ofthe southern California citrus soils. Similarstudies could be done with other crops to de-termine which soils require mycorrhizal in-festation.

POTENTIAL USES FOR MYCORRHIZAL FUNGI

Because mycorrhizal fungi occur on most Large-scale field inoculations with mycorrhizalagronomic crop plants and improve the growth fungi are rare because of limited inoculum, andof these plants, the potential use of these fungi natural field soils usually contain adequateas commercial “biotic fertilizers” is enormous. populations of indigenous mycorrhizal fungi.

196

Under these conditions, any growth benefitdue to mycorrhizal inoculation would dependprimarily on the superiority and/or placementof the mycorrhizal inoculum. Beneficial re-sponses under these conditions would be pre-dicted to be far less than the responses obtainedin fumigated or partially sterilized soil. How-ever, greenhouse and field experiments inwhich plants were inoculated with mycorrhizalfungi in nonfumigated soils have demonstratedthat growth responses due to mycorrhizal fungican occur under these circumstances.

In greenhouse experiments, using untreatedsoil, Mosse and her colleagues (62,63,65,67,70)demonstrated that preinoculation with mycor-rhizal fungi could provide the following growthincreases:

Crop Growth increaseCentrosema spp. . . . . 34 percentcorn . . . . . . . . . . . . . . . 306 percentMelinis spp. . . . . . . . . 41-60 percentonions . . . . . . . . . . . . . 48-3155 percentstrawberries . . . . . . . . 250 percentStylosanthes spp. . . . 85-88 percentsweetgum . . . . . . . . . . 45 percentViola spp. . . . . . . . . . . 527 percentOther studies have noted similar growth increases in untreatedsoil:corn . . . . . . . . . . . . . . . 14 percent (Gerdemann, 1964)corn . . . . . . . . . . . . . . . . 0-53 percent (Jackson, et al., 1972)mahogany . . . . . . . . . . 151 percent (Redhead, 1975)sudangrass . . . . . . . . . . 0-18 percent (Jackson, et a]., 1972)white clover . . . . . . . . 80-100 percent (Powell, 1977)

In a large-scale field experiment conductedin nonsterile, virgin, infertile fields, wheat pre-inoculated with a mycorrhizal fungus pro-duced 220 percent more grain than non-mycor-rhizal wheat (41). In a similar experiment (40),corn inoculated with a mycorrhizal fungus was122 percent larger than non-mycorrhizal corn.Hayman (33) reported white clover growth in-creases in the field due to inoculation with amycorrhizal fungus. Black and Tinker, in anextremely well-documented field experiment,found that fallow field inoculation with a my-corrhizal fungus increased potato yield 20percent.

Not all mycorrhizal inoculations in nonster-ile soil result in increased growth. Hayman (33)indicated that mycorrhizal fungi did not stim-ulate growth of white clover at several loca-tions. Powell (75) obtained significant growth

increases of white clover after inoculation withmycorrhizal fungi in only three of nine sites.Jackson, et al. (38), indicated that with certainmycorrhizal inoculation methods, growth ofcorn, sudangrass, and soybeans was not stim-ulated in nonsterile soil. Mosse (65) obtainedsignificant growth responses of Stylosanthesspp. due to mycorrhizae in 6 of 11 nonsterilesoils. Ross and Harper (85) reported no growthstimulation of soybeans in nonsterile soil.

Mosse (65) indicated that the inoculum po-tential of indigenous mycorrhizal fungi is themajor determinant governing growth responsesof plants to mycorrhizal fungi in nontreatedsoil. Powell (75) indicated that many indige-nous mycorrhizal fungi are “inefficient” sym-bionts, and that inoculation by more efficientmycorrhizal fungi will result in growth in-creases even in nonsterile soil that contain highpopulations of “inefficient” mycorrhizal fungi.placement of mycorrhizal inoculum is equallyimportant in affecting a plant growth response(38). Certainly, plants infected early in thegrowing season by mycorrhizal fungi are bet-ter than plants that do not become infected un-til later (82).

Huge expanses of tropical soils (e.g., the Bra-zilian Cerrado) are either deficient in phos-phorus or immobilize phosphorus fertilizers.These marginal agricultural lands could be pro-ductive if mycorrhizal fungi, with the abilityto efficiently use extremely small quantities offertilizer, were developed and added to the soil.Cheap but readily available rock phosphatecould be added as the phosphorus source. Thisphosphorus source is a poor fertilizer but re-leases small quantities of phosphorus for longperiods of time. Some mycorrhizal fungi userock phosphate much better than others andcan tremendously improve growth of plantsgrowing in poor soils fertilized with this ma-terial (59,66).

Mycorrhizal fungi have been proposed as un-stable soil or sand dune stabilizers (96). Finallyectomycorrhizal fungi have been shown to im-prove rooting of a wide variety of non-hostplants and the possibility of using them as acommercial root stimulant has been proposed(45).

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CONSTRAINTS ON THE COMMERCIAL USE OFMYCORRHIZAL FUNGI

The current major obstacles to the commer-cial use of mycorrhizal fungi are:

c the lack of large-scale field experimentsunder normal agricultural conditions,

Q the lack of cost-benefit analysis to deter-mine the economics of mycorrhizal appli-cations, and

● the trend toward excessive fertilization tosubstitute for the lack of mycorrhizalfungi.

Perhaps the most important deterrent of com-mercial use of mycorrhizal fungi is the lack oflarge-scale field tests in a variety of agriculturalsoils and locations. The program initiated byD. H. Marx and the U.S. Forest Service willcorrect this deficiency for ectomycorrhizal fun-gi and within 4 years it will be known if thesemycorrhizal fungi will indeed be economicallyfeasible to use on a wide scale in the produc-tion of forest trees.

This type of program remains to be establishedfor VA mycorrhizal fungi. Without such datait is difficult to establish a potential market formycorrhizal inoculum. Without a market thereis little incentive for industry to initiate the pro-duction of commercial inoculum. Without com-mercial inoculum it is difficult to carry outlarge-scale field tests. With the recent establish-ment of several commercial sources of mycor-rhizal inoculum perhaps this cycle will be bro-ken and more field tests will result.

Once large-scale field tests are seen to be suc-cessful, light-weight commercial mycorrhizalformulations will develop and new applicationmethods will be devised, Most importantly,from large-scale field tests, cost benefit analy-sis can be accurately done to determine theeconomic benefit derived from the use of my-corrhizal fungi. In the end, this will be the de-termining factor in the commercial applicationof mycorrhizal fungi. Biological scientists arerarely able to critically assess the economic fac-tors involved in the application of a new tech-nique and I recommend that agricultural econ-omists should be asked to participate in the

cost-benefit assessment of VA mycorrhizal in-oculation.

Heavy phosphorus fertilization severely in-hibits mycorrhizal infections (17,68). Morerecently, it is becoming evident that heavy ni-trogen and zinc applications are also inhibitoryto mycorrhizal fungi (32,51). Daily applicationsof 100 ppm nitrogen under greenhouse condi-tions have been shown to completely eliminatemycorrhizal infections (J.A. Menge, unpub-lished data). Many commercial greenhousesadd over 200 ppm nitrogen daily to their plants.In greenhouse and fumigated nursery condi-tions, growers are using excessive fertilizationto substitute for the lack of mycorrhizal fungi.Under these conditions, not only do mycorrhi-zal fungi not benefit their host plants, but it isdifficult to successfully establish mycorrhizalinfections so that the plants will be mycorrhizalonce they leave the supraoptimal fertilityregime. As long as fertilizer is relatively avail-able and not excessively expensive, it will takea major educational program to convince manygrowers to change their standard operatingprocedures and use mycorrhizal fungi that willnot only be cheaper but will conserve fertilizerand energy.

In my opinion, granting agencies such as theNational Science Foundation, RockefellerFoundation, USDA competitive grants, and theIsraeli-U.S. granting agency BARD have effec-tively provided adequate funding for basic my-corrhizal research. The number of scientificpapers on mycorrhizal fungi has quadrupledsince 1960, which is evidence that there is greatinterest and money available for basic mycor-rhizal research. However, there are few agen-cies that will fund the final applied steps in abiological commercialization project. Researchmoney for large-scale “applied” or “demonstra-tion” experiments is unavailable. Funding forsmall-scale pilot projects is also not available.It remains for private industry to pick up theprojects from this point, but they have been re-luctant to do so. The transition is not goingsmoothly and seems to be proceeding slowlyif at all,

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It is very difficult for a scientist to speculateon the effects of a new procedure on the socialand economic structure of an agricultural so-ciety. Frequently good ideas do not receive theacclaim they deserve because of prejudices, ig-norance, religious preferences, social mores,and other reasons not fully understood by sci-entists. In my opinion, the effects of mycor-rhizal technology would most alter the socio-economic structure in areas of intensive agri-culture. These situations would be more prev-alent in agriculture in developed nations.Mycorrhizal fungi are most useful in reclaim-ing sites disturbed by heavily mechanized in-dustries or soil fumigation. Mycorrhizal fungican reduce energy and fertilizer and increasethe efficiency of crops grown intensively.Therefore, mycorrhizal fungi can be viewed asconservation measures or as substitutes forhigh energy uses in developed nations.

In less developed nations, growers wouldhave to be educated to the methods of produc-ing, handling, and inoculating living micro-organisms. This may be difficult. In countries

FUNGI ON AGRICULTURE

with a less well-developed agricultural system,mycorrhizal fungi have not been altered andare probably functioning effectively and neednot be applied under such conditions. Fertilizerin most underdeveloped countries is probablyapplied sparingly as manure and therefore my-corrhizal fungi will not result in a great sav-ings either of fertilizer or energy.

If superior strains of mycorrhizal fungi aredeveloped, marginal agricultural land could bemade productive. Huge amounts of marginalagricultural land exists in Africa and SouthAmerica and the proper use of this land maywell decide the future of some countries. In-creased use of agricultural land will providefor a greater economic base, larger agriculturalproductivity, and a better way of life for largepopulations in underdeveloped countries. Edu-cating agriculturists to the importance of my-corrhizal fungi may allow developing countriesto avoid the excessive use of energy, fumigants,and fertilizers associated with intensive agri-culture.

Mycorrhizal fungi may be one alternativethat can immediately improve revegetation ofdisturbed sites, increase crop growth in fumi-gated soils and greenhouses, and yet reducefertilizer costs and energy demands. If superiorstrains of mycorrhizal fungi were developed,they could potentially improve growth of near-ly all agronomic crops in a wide variety of soilsthroughout the world. Both ectomycorrhizalfungi and vesicular-arbuscular mycorrhizalfungi are in commercial production on a smallscale. The greatest obstacles to the commercial-ization of mycorrhizal fungi appears to be: 1)the lack of large-scale field tests under typicalagricultural conditions in a variety of locations;2) adequate cost-benefit analysis to determinethe economics of the utilization of mycorrhizalfungi; and 3) a reluctance on the part of grow-ers to switch from an energy dependent, heavy

fertilizer system to a new, but cheaper, energyconservative system using mycorrhizal fungi.

Recommendations that could substantiallyincrease the commercial use of’ mycorrhizalfungi (in relative order of importance) are asfollows:

1. Improved availability of grant funds forlarge-scale field applications of mycorrhi-zal fungi in a wide variety of soils through-out the world. It would be useful to estab-lish several pilot projects in various lessdeveloped countries. These pilot projectscould produce and distribute mycorrhizalinoculum on a variety of crops growingunder different soil conditions. Cost-ben-efit analysis on such projects could ade-quately assess the economics of inocula-tion with mycorrhizal fungi.

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2.

3.

4.

5.

6.

7.

Funds should be made available to createa worldwide bank of beneficial mycorrhi-zal fungi. The establishment of such afacility is being investigated by the mycor-rhizal community and the National Sci-ence Foundation has agreed to entertaina proposal for such a facility. The Univer-sity of Florida has agreed to supply the fa-cilities as well as substantial operatingcosts for such an establishment. A secondidea would be to add the responsibility formaintaining mycorrhizal cultures to thealready established government facilitycalled the American Type Culture Collec-tion which maintains many importantfungal cultures.It would be desirable to establish a USDA-supported vesicular-arbuscular mycorrhi-zal research center that would be respon-sible for maintaining and coordinatingU.S. research on mycorrhizal fungi. Thisfacility would complement the Mycorrhi-zal Institute in Athens, Georgia, which wascreated by the Forest Service to coordinatemycorrhizal research on forest trees.A world survey should be conducted tocollect and test as many different vesicu-Iar-arbuscular mycorrhizal species as pos-sible. The discovery of a superior mycor-rhizal strain with a wide host range couldtremendously increase agricultural pro-ductivity throughout the world.Research is necessary to elucidate the ex-act role of mycorrhizal fungi play in im-proving plant growth under stress condi-tions such as drought, salt, toxic soilmaterials, or in marginal agriculturallands.Research is necessary to elucidate the ge-netics of mycorrhizal fungi. Virtuallynothing is known on this subject. Theability to breed these organisms could re-sult in tremendously increased agricul-tural productivity.Efforts should be intensified to grow ve-sicular-arbuscular mycorrhizal fungi in thelaboratory using artificial media. Abreakthrough in this area could improvethe feasibility of attaining all of the aboverecommendations, However, since scien-

tists have been trying to artificially cultureVA mycorrhizal fungi since 1900, this ob-jective may be difficult to achieve and in-centives to work on such a problem are dif-ficult to justify.

References

1. Bagyaraj, D. J., and Menge, J. A., “Interaction

2,

3,

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6.

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9.

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11.

Betweeen VA Mycorrhiza and Azotabacterand Their Effects on Rhizosphere Microfloraand Plant Growth, ” New I%ytol. 80: 567-573,1978.Baylis, G. T. S., “Experiments on the Ecologi-cal Significance of Phycomycetous Mycorrhi-zas,” New l%yto~. 66: 231-243, 1967.Backman, P. A., and Clark, E, M., “Effect ofCarbofuran and Other Pesticides on Vesicular-Arbuscular Mycorrhizae in Peanuts, ” Nema-tropica 7: 13-15, 1977.Becker, W, N., “Quantification of Onion Vcsic-ular-Arbuscular Mycorrhizae and Their Resis-tance to Pyrenochaeta tarrestris, ” Ph. D. thesis(University of Illinois at Champaign-Urbana,1976).Benians, G. J., and Barber, D. A., “Influenceof Infection With Endogone Mycorrhiza onthe Absorption of Phosphate by BarleyPlants, ” Letcombe Lab. Ann. Rpt., 1971: 7-9,1972.Bieleski, R, L., “Phosphate Pools, PhosphateTransport and Phosphate Availability, ” Ann.Rev. P]ant Physiol 24: 225-252, 1973,Black, R. L. B., and Tinker, P. B., “InteractionBetween Effects of Vesicular-Arbuscular My-corrhiza and Fertilizer Phosphorus on Yieldsof Potatoes in the Field, ” Nature 267: 510-511,1977.Bowen, G. D., “Nutrient Status Effects on Lossof Amides and Amino Acids From PineRoots,” Plant and Soil 30: 139-143, 1969.Chapman, H. D., and Rayner, D. S., “Effect ofVarious Maintained Levels of Phosphate onthe Growth, Yield Composition and Quality ofWashington Naval Oranges, ” Hilgardia20:325-358, 1951.Chatfield, J. A., Rhodes, L. H., and Powell, C.C., “Mycorrhiza in Floriculture, the PotentialUse of Beneficial Fungi in Flower Crops, ”Ohio Florists’ Assn., Bull, No. 594: 5-6, 1979.Cooper, K. M., “Growth Responses to theFormation of Endotrophic Mycorrhizas inSolarium, Leptospermum and New Zealand

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38-846 0 - 85 - 8

Chapter XI

A Low Fertilizer Use Approachto Increasing Tropical Food

Production

William C. LiebhardtPlant Science Department

University of DeIawareNewark, Delaware

Contents

Page

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .”””.”.”” ““”...”.””””’””... 207The Tropics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ., . . . . ..,.””.’” “’””.,... 207Land Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ““””””..”.””+ 208Farming Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .“.”.””” 208Tropical Food Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .....”.”” 209Soil Fertility Concepts—A General Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209Soil Acidity and Liming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210Finding the Correct Lime Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..#.........”...””’o” ““.”””. 212Nitrogen Supply Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212Biological Nitrogen Fixation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213Productivity of Improved Grass-Legume Mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214Nitrogen Release From Organic Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214Phosphorus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215Management of Phosphorus Fertilizer . . . . . . . . . . . . . . . . . . . . . . . . . . . + . . . . . . . . . . 215Sources of Phosphorus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216Sulfur Deficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ... ... .....$. ... ..””..O 217Potassium Deficiency. ....< .. .. .+ ... . ~ .......,. ...........~....’” . . . . . . . . . 218Rice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .“”. 218Plants That Tolerate Adverse Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . “.””’”.”.. 221

Chapter Xl

A Low Fertilizer Use Approach toIncreasing Tropical Food Production

ABSTRACT

Low fertilizer use in the Tropics appears tobe a desirable goal and it could involve severalstrategies aimed at increased crop productionwith minimal use of inputs.

According to the general response curve thatshows the effects of added nutrients, the useof small amounts of an input may result in sub-stantially increased production. The philoso-phy employed here is to use less than maxi-mum inputs to achieve the highest output:input ratio or to make maximum use of inputsrather than to maximize yields. That often re-quires a much greater use of scarce inputs suchas fertilizer, capital, etc.

Because they have inherent high fertility, lim-ited inputs are needed on the “high base soils”(18 percent of tropical soils) when there is suffi-cient water, Small amounts of nitrogen, phos-phorus, and/or micronutrients are sufficient.High yielding varieties should be used on thesesoils to take advantage of the naturally high soilfertility.

On the “low base soils” (51 percent of tropi-cal soils), which have high soil acidity and alu-minum and the associated phosphorus defi-ciency, the production package should beconsiderably different. Lime may be necessaryto reduce the availability of toxic aluminum.This will also increase the availability of phos-phorus. However, additional phosphorus and/

or sulfur will probably be necessary to increaseyields.

The use of crops that will tolerate adversesoil conditions should also be employed onthese soils. This reverses the philosophy ofchanging the soil to fit the crop (an expensiveprocedure on these soils) to one that takes thesoil as it is (or changes it minimally) and usescrops that grow well under existing conditions.Examples of such crops are upland rice, cas-sava, sweet potatoes, cowpeas, and some grassand legume pasture crops.

With both high and low base soils, nitrogenis probably the most limiting element. Lowyields in many tropical areas reflect a low levelof nitrogen availability. Low yields and the lackof nitrogen result in low levels of protein forlocal human consumption, causing malnutri-tion. An excellent source of protein and nitro-gen are leguminous crops. These crops havethe potential to biologically fix nitrogen fromthe atmosphere when growing in associationwith the correct bacteria. When these crops areused, the nitrogen input into the cropping sys-tem can be increased several fold. This tech-nology is inexpensive, easy to use, and avail-able. Most important, it can substantiallyincrease the yield of crop plants as well as meatand milk production to the benefit of the smaIIfarmer and the landless poor.

THE TROPICS

The Tropics are that area of the world lo- lion people in 1975) live in this area. Most ofcated between 23.50 north and south of the the world’s developing countries lie in theEquator. Thirty-eight percent of the Earth’s Tropics, although some areas in the Tropics areland surface (about 5 billion hectares) and 45 not considered developing and many develop-percent of the world’s population (about 1.8 bil- ing countries are outside the zone.

207

208

Because of the proximity to the Equator, theTropics experience little change in temperatureduring the year. Variation of daylength is alsorelatively small compared to temperate zones.Rainfall is the variable which differentiatestropical areas. About one-quarter of the Trop-ics, mostly those near the Equator, have a rainyclimate. Seasonal climates—those with a dis-tinct wet and dry period—cover about one-halfof the Tropics. Dry climates, usually having ashort wet season, cover 16 percent of the Trop-ics. Tropical deserts comprise the remainingarea, about 11 percent.

In 1960, the world’s population reached 3 bil-lion; by 20006 billion will inhabit the Earth.Much of this population increase is takingplace in the Tropics, primarily in Asia. This

About 10 percent of the tropics are cultivatedfor food production; pastures and meadows ac-count for an additional 20 percent. The Presi-dent’s Science Advisory Committee estimatedthat only 500 million hectares were croppedin 1967 even though the potential for cultiva-tion was 117 billion hectares. Grazing occupied1 billion hectares, but the potential was 1.6 bil-lion hectares. These figures indicate that there

Common farming systems in the Tropics are(56):

1. shifting cultivation, where the land iscropped and then abandoned when yieldsfall, covers 45 percent of the Tropics;

2. settled subsistence farming is practiced on17 percent of the Tropics;

3. nomadic herding covers 14 percent of thearea;

4. livestock ranching uses 11 percent; and5. plantation systems, which cover 4 percent

of the tropical area.

population explosion will place a much greaterstrain on the resources of the Tropics. Malnu-trition, particularly protein deficiency, is wide-spread throughout the area. Protein deficiency,a lack of high protein food, is related to a lackof nitrogen in the soil-plant system.

Protein synthesis in the plant only occurswhen there is sufficient nitrogen in the soils,therefore, a lack of soil nitrogen decreases therate of protein production in plants and hence,in the food supply. Inexpensive and efficientmeans to increase nitrogen in the tropical sys-tem are known. Use of these simple technolo-gies could increase protein production andeliminate much of the misery and suffering inthe Tropics caused by poor nutrition.

USEis much potential to expand in agricultural pro-duction in the Tropics.

The use of land will vary depending on soilfactors, climate, economic, social, and politi-cal factors. In general, the farming systems arevastly different than those practiced in theUnited States.

SYSTEMSIf food production is to be increased and the

majority of people benefit, programs must beaimed at the small farm rural population sincesmall farms are the most numerous. In tropi-cal Asia, 75 percent of all farms are smallerthan 2 hectares (5 acres) (36). Sixty-nine per-cent of Central American farms are smallerthan 5 hectares (12 acres) (14). The averagefarm size of 20 tropical African countries re-porting such data in the 1973 FAO ProductionYearbook was 5.4 hectares. Studies by CATIE(14) and Pinchinat, et al. (53), showed that about70 percent of the food consumed in Colombia

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and Central America is produced on smallfarms. Therefore, any strategy dealing with

Common tropical crops are sugarcane, pine-apple, bananas, coffee, and tea. These crops,however, contribute little to the nutrition ofpeople in the Tropics because they are ex-ported, largely to the temperate zone. The ma-jor food crops consumed by tropical people arerice, cassava (root crop), corn, sweet potatoes,yams, wheat, sorghum, peanuts, potatoes, anddry beans (in order of decreasing importance).The total area cultivated for these 12 crops isonly 300 million hectares compared to 1 bil-lion hectares of pasture and meadow.

food production in the Tropics must deal withthe small farmer.

FOOD CROPS

and likely to remain that way in the near fu-ture. But on the positive side, the soils and cli-mate provide a resource base that can expandproduction and help meet these food needs.The introduction of simple technologies couldgreatly increase food production, helping tostabilize these countries in many ways.

Much of this increase must come from a bet-ter use and understanding of the tropical soils’capacity to produce. Therefore, the bottom linequestion becomes a question of soil fertility.

The Tropics can be characterized as a regionwhere population pressures are often highest

SOIL FERTILITY CONCEPTS-A GENERAL STATEMENT

A fertile soil has the capacity to produce ahigh yielding and high quality crop. More spe-cifically, it is a soil that does not limit produc-tion because of physical, chemical, or biologi-cal constraints.

Numerous essential elements are requiredfor crop production, including carbon, hydro-gen, oxygen, nitrogen, phosphorus, potassium,calcium, magnesium, sulfur, iron, copper, bo-ron, zinc, manganese, and molybdenum. Thefirst three are obtained from water and the car-bon dioxide in the atmosphere. The rest mustbe taken up from the soil by the plant’s rootsystem. Another important element is alumi-num. Although not considered essential togrowth, if excessive, it is severely toxic toplants and can reduce plant growth and cropyield.

Soil tests attempt to predict crop yield for anumber of elements. These tests determine asnearly as possible the soil’s capacity to supplythe elements necessary for plant growth.where the soil’s supply is considered insuffi-cient for a desired yield, additional amend-

ments are supplied to the soil increasing its“fertility,” or ability to produce.

A typical soil test crop response curvefollows:

The response curve has three general areas.Area “a” is the part of the curve where smallinputs of nutrients result in increasingly great-

Relative soil test value

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er production, i.e., the output: input ratio isfavorable. Area “b” is a relative plateau whereincreasing fertilizer inputs do not result in in-creasing yields and the output: input ratio ispoor since yield can be maximized at a lessorinput rate. Area “c” represents the portion ofthe curve where additional nutrients actuallyreduce yield because of excessive or toxic con-centrations. Obviously this is a situation to beavoided. This is the situation with aluminumin many unlimed soils of the Tropics.

A few simple equations help to explain therelationship between the soil and plant nutri-ents. The general relationship between ele-ments in the soil and plants maybe seen in thefollowing, where E represents an element usedin plant growth.

Soil solid phase(E) Soil solution phase(E)Plant root(E) Plant top(E)

As the above equation indicates, an element istaken in by plant roots and moved to the planttop as a soluble element dissolved in the soilsolution. Elements are generally considered tobe available when they are in the solution phaseof the soil. In many instances an element is un-available to the plant because it is not in a formthe plant can use, that is, not in solution. An-other equation helps to explain the soil fertil-ity-plant nutrition relationship. Again, E rep-resents an element necessary for plant growth.

This simple equation shows the equilibrium inthe soil that determines if the nutrient can beused by a plant. This equilibrium is controlledby the soil environment: soil pH, micro-orga-nisms, oxygen, water, temperature.

Soil pH is a term used to delineate the rela-tive acidity or alkalinity of soils. It is impor-tant because soil pH affects the availability ofmost nutrients. The soil pH scale follows:

1 2 3 4 5 6 7 8 9 10 11 12 13 14

More acid Neutral More alkalineor basic

Early in history, man learned to cultivate highbase soils (soils high in calcium, magnesium,and potassium and low in aluminum) becausethey are naturally more productive. The ma-jority of cultivated soils of the Tropics are notacid (56), although the majority of soils of thehumid Tropics are acid. Soils of tropical Amer-ica are more acid than those of tropical Africaand Asia.

Liming of acid soils has been a longstandingpractice. For a long time, the practice involvedadding sufficient lime to raise the soil pH to7 (neutrality). However, in the early 1950s soilchemists showed that exchangeable aluminum,toxic to plants, was the predominate elementin acid mineral soils as contrasted to organic

soils (18). Exchangeable elements such as cal-cium, magnesium, and potassium are positive-ly charged and are held in the soil by negativelycharged sites. Strongly acid soils (pH less than5.0) favor aluminum availability to plants,whereas above pH 5.5, calcium, magnesiumand potassium prevail.

High soil solution aluminum, the availableform for plants, causes reduced plant growthbecause aluminum is toxic to plants. Evans andKamprath (25) found that an exchangeable alu-minum saturation of 60 percent was requiredbefore a large amount of aluminum was pres-ent in the soil solution. Work in Guyanashowed that an aluminum saturation of lessthan 60 percent resulted in less than 1 ppm—1 part per million—in the soil solution (13). In-creasing fertilizer results in an increase of alu-minum in the soil solution (34). Therefore, useof high amounts of fertilizer could increase alu-minum toxicity if the soil is sufficiently acid.Available aluminum in the soil solution de-creases with increasing organic matter sincealuminum forms very strong complexes, mak-ing it unavailable.

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Research by Kamprath (42) showed that elim- 10W. Growth of sugarcane was severely de-ination of all the exchangeable aluminum was pressed on a soil with an exchangeable alumi-not necessary to obtain maximum yield in field num saturation of 70 percent. Addition of limeand greenhouse studies. Maximum yields of to reduce the aluminum saturation to 30 per-corn, soybeans, and cotton were achieved with cent resulted in a four-fold increase in sugar-aluminum saturation values of less than 45, 20 cane growth (l).and 10 percent respectively where soil pH was

FINDING THE CORRECT LIME LEVEL

The work cited above, plus other work, hasshown that lime should be added to reduce thetoxic levels of aluminum. This results in amuch lower soil pH and the use of much lesslime than the traditional approach of liming toneutrality. Liming beyond this point has re-sulted in reduced yields on soils of the Trop-ics because of deficiencies of manganese, zinc,and/or iron. Like aluminum, manganese be-comes available as the soil becomes more acid(7). Some soils are low in aluminum but highin manganese. In either case, liming will re-duce the availability of manganese. However,since manganese is an essential element, lim-ing must not be so high as to make the elementunavailable and reduce the soils productivity.

A wise liming philosophy, therefore, shouldbe to add sufficient lime to decrease the avail-ability of aluminum without limiting manga-nese to the point of deficiency. The factors tobe considered are: 1) the amount of lime neededto decrease the percent of aluminum satura-tion to a level where the particular crop andvariety will grow well, 2) the quality of lime,and 3) the placement method (56). Kamprath(42) suggests that lime recommendations bebased on the amount of exchangeable alumi-num and that lime rates be calculated by mul-tiplying the milliequivalents (meq) of aluminumby 1.5, to find the meq of calcium needed aslime. Lime rates calculated by this method neu-tralize 85 to 90 percent of the exchangeable alu-minum in soils with 2 to 7 percent organic mat-ter, which includes the majority of soils.

This method has been successfully used inBrazil since 1965 and is employed in most

American countries. The application of thisformula has reduced rates of liming substan-tially, particularly in acid, highly leached soilslow in cation exchange capacity (this term re-fers to the amount of negatively charged sitesin the soil). In most cases where 1 to 3 meq ofexchangeable aluminum is present, lime appli-cations are now on the order of 1.6 to 5 tonsper hectare. In the past, rates of 10 to 30 tonsper hectare were frequently used with mixedresults.

Different crops tolerate different levels of alu-minum. Crops such as cotton, sorghum, andalfalfa are susceptible to levels of 10 to 20 per-cent aluminum saturation, therefore, limingshould be aimed at zero aluminum for thesecrops. Corn is sensitive to 40 to 60 percent alu-minum saturation, therefore, 20 percent alu-minum saturation could be more economicalfor corn. Other crops such as rice and cowpeasare more tolerant than corn. Coffee, pineapple,and some pasture species seldom respond tolime, even in soils with high aluminum sat-uration.

Sources of lime are difficult to find in theTropics. If possible, lime should contain bothcalcium and magnesium. The coarseness of thelime also affects its usefulness. Coarse lime,that which does not pass through a 20 meshsieve, will have very little reactivity; lime thatpasses through a 60 mesh sieve will react veryslowly. Fine lime, which passes a 100 meshsieve, will react quickly. Generally, a goodgrade of fineness is more than 60 mesh; a bet-ter grade is 100 mesh. Lime is commonly mixedin the top 6 to 8 inches of soil. In Puerto Rico,

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Abruna, et al. (z), observed no differences in cases, plants suffer from water stress duringpasture yields between surface-applied and short-term droughts even though the subsoil issoil-incorporated lime. still moist. Studies show that deep placement

When very acid leached soils are limed to pHof lime resulted in deeper root development,diminished water stress during drought, and

5.5, most of the root development occurs in thetopsoil. The highly toxic aluminum in the sub-

increased corn yield of 20 to 25 percent (56).

soil prevents deeper root development. In such

NITROGEN

Nitrogen, too, is very crucial to crop produc-tion and the availability of protein to tropicalpeople. Acid soils contribute to that problemlargely because soil acidity reduces nitrogenfixation by leguminous plants. In nitrogen fix-ation, the nitrogen of the atmosphere is madeavailable to plants. Next to water, nitrogen isthe most limiting factor in crop production inthe Tropics. It is necessary for protein synthe-sis and production. Plant-available nitrogen is

derived from organic matter, leguminous ni-trogen fixation, fertilizers, and animal manure.The main source of nitrogen in the Tropics isthe decomposition of organic matter. There-fore, practices that maintain organic matter inthe soil are essential. Organic matter not onlyprovides nitrogen, but it improves the soil’sphysical condition and water-holding capac-ity, increasing water to plants and decreasingthe soil temperature.

NITROGEN SUPPLY PROCESS

Nature has provided the nitrogen for cropproduction since the beginning of time throughnatural processes. However, seldom has it pro-vided an abundance of nitrogen for long andsustained periods of crop production on thesame piece of land. Moreover, natural proc-esses at their best have seldom providedenough plant-available nitrogen to achieve thelevel of food and fiber production needed tomeet the demands of present day crop produc-tion. Natural nitrogen-supplying processes in-clude: 1) mineralization of nitrogen from soilorganic matter and from crop residues; 2) thereverse process of immobilization in the de-composition of plant and animal debris and soilorganic matter; 3) fixation of nitrogen from theatmosphere, largely through biological proc-esses; 4) addition of nitrogen through rain andother forms of precipitation (5).

The nitrogen in soil organic matter is impor-tant for crop production, However, soil nitro-gen is not inexhaustible; it declines in quanti-ty in the soil as it is used by crops grown,

harvested, and consumed. Nitrogen in soil islargely organic, replenished by periodic addi-tions of fresh plant or animal residues.

Under normal conditions, nitrogen is addedto the organic supply in soil each year throughcrop residues (immobilization), but it is unavail-able to plants. Also through biological decom-position, organic nitrogen in the soil is continu-ously converted to the inorganic form (miner-alization), which is available to plants. Underany sustained system of crop and soil manage-ment, these two processes tend to approacheach other in magnitude so that mineralizationbalances immobilization (9). When this balanceis attained, the system is considered to be inequilibrium.

The implications and consequences of anequilibrium in the soil’s organic nitrogen needto be emphasized. At equilibrium, the amountadded to the supply of organic nitrogen is es-sentially balanced by a like amount of decom-position. The total quantity of soil nitrogen re-

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mains unchanged and the net amount that canbe and is supplied to a crop is zero (5). Duringperiods of virgin or noncultivated conditions,such as a forest, certain soils tend to build uporganic matter, accumulating as much as10,000 kg/ha of nitrogen under virgin condi-tions. During the first years of cultivation, thesesame soils may supply as much as 400 kg/haof available nitrogen per year to crops (59). Ascultivation continues and the organic nitrogendeclines, the quantity of nitrogen becomingavailable each year also declines. After longperiods of cultivation, the soil’s organic mat-ter becomes exhausted unless legumes are grownor the soil fertilized with nitrogen. A minimalamount of nitrogen is supplied by rainwaterand nonsymbiotic nitrogen fixation.

Many of the major land areas of the Tropicshave now been cropped for extended periodsand the organic matter stored under virgin con-ditions has been dissipated. With little or nouse of nitrogen fertilizer, tropical crop yields

reflect the paucity of the natural nitrogen sup-ply from rainwater and nonsymbiotic nitrogenfixation.

Yields of corn of 600 to 1200 kg/ha and ofwheat of 400 to 800 kg/ha require a nitrogensupply only a little larger than could be ex-pected from rain and from nonsymbiotic fixa-tion. Yields this poor remove no more than 15kg/ha of nitrogen from the land in the harvestedgrain products. Such minimal yields can besustained for a long period of time without fer-tilizer or legumes, but do little to sustain theprotein needs of animals or humans.

However, with inclusion of legumes in therotation either as a primary food crop or as agreen manure, the nitrogen supply in the soil-plant system can be increased substantially.This will result in increased crop and proteinproduction, helping to meet the primary mal-nutrition problem of the Tropics.

BIOLOGICAL NITROGEN FIXATION

Despite the great use of chemical fertilizertoday, biological nitrogen fixation processeshave been responsible for providing most of thenitrogen currently used by and tied up in plantsand animals and in the decomposed residuesfound in soil. It supplies the major part of thenitrogen for crop production in world agri-culture.

According to reviews by Henzell and Norris(37) and Jones (4)), Rhizobium bacteria fixationaccounts for 100 to 300 kg of nitrogen per hec-tare and year. Whitney (67), however, reportsan annual range of 47 to 905 kg of nitrogen perhectare for pure stands of an improved vari-ety of Leucaena leucocephala.

Obviously, the potential to increase the ni-trogen in a cropping system several fold (15kg/ha v. several hundred kg) using legumes incrops or pastures is possible. Differencesamong adapted species within a specific envi-ronment seem to be closely related to dry mat-ter production (total growth) (40). This suggests

that there is little difference in the capacity oflegumes to fix nitrogen as long as they areadapted to the environment. Factors affectingdry matter production, such as moisture or nu-trient stress, solar radiation, diseases, and otherfactors will determine nitrogen fixation.

pastures and meadows make up the greatestportion of the land that is managed for foodconsumption, therefore, potential increases infood are large if this segment of tropical pro-duction could be increased. Another importantfactor to consider is that production from pas-tures and meadows results in increased meatand milk, both high in quality proteins.

Some individuals consider cattle to be a veryinefficient source of protein for humans in thefood chain. This is true when animals and hu-mans compete for grain. It is not true when cat-tle convert forage from pasture and meadowlands into meat and milk. The determining fac-tor will be how much and what kind of landis available for cultivation.

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Beef production will normally increase by afactor of 2 to 4 due to establishment of grass-legume mixtures (40). Few experiments providelong-term data. Sanchez (56) cites a study ofa legume, Stylosanthes humilis introduced intoa Queensland pasture and followed beef pro-duction for 7 years. The following table sum-marizes the results:

Beef Production Systems in the Tropics

Treatment Beef kg/haGrass alone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Grass & fertilization* . . . . . . . . . . . . . . . . . . . . . . . 62Grass & legume . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93Grass & legume & fertilization* . . . . . . . . . . . . . . 148● Annual application 10 kg P/ha as0O-20-0 and 40 kg K/ha plus Mo.

It is interesting to note that the grass-legumetreatment produced more beef than did the fer-tilizer treatment. The grass-legume mixtureplus fertilizer more than doubled the beef pro-duced by grass alone plus fertilizer, demon-strating the effect of adding nitrogen to the sys-tem via the legume.

Another plant, a fern, Azolla, grows in asso-ciation with rice, the major crop of Asia. Azolladoes not fix nitrogen itself, however, it growsin symbiotic association with blue-green algaeAnabaena azollae (16). About 10 percent ofChina’s rice (3.2 million acres) are grown withAzolla. He states that yields of rice of 6 tonsper acre have been reported along with 60 tonsof Azolla. Rice with conventional fertilizersyields about 4 tons per acre. Preliminary ex-periments indicate that Azolla will produce so

to 180 pounds of nitrogen per acre, making ithighly attractive as a natural nitrogen source.

Another nitrogen fixing system has been re-ported by Dobereiner and her associates in Bra-zil (20,22). Their work has focused on nitrogenfixation by nonleguminous plants. This workhas a great potential if efficient strains of bac-teria can be found. At present, this rate ofasymbiotic fixation contributes only about 10kg of nitrogen per hectare per year.

Recent evidence suggests that symbiotic ni-trogen fixation takes place in some tropicalgrasses (22). The nitrogen fixation takes placein the rhizosphere (soil close to root), however,since this nitrogen is taken up directly byplants, it is considered symbiosis. Laboratoryexperiments suggest that the magnitude of thismechanism may be on the order of 1 kg of ni-trogen per hectare per day. This system needsto be taken out into the field to determine ni-trogen fixation under more realistic conditions.

Field beans, Phaseolus vulgaris, a staple inmany Latin American countries, appear to fixlittle nitrogen (56). This is attributed to poormodulation characteristics that may be due tolow phosphorus or high aluminum which in-hibit Rhizobium activity. When these legumesare grown, they contribute nitrogen to thesystem. It eventually becomes available viamineralization or the breakdown of complexnitrogen compounds into simpler nitrogencompounds.

Plant-available inorganic nitrogen in mosttropical areas shows a marked seasonal fluc-tuation (56). This is characterized by a slow ni-trate (available form to plants) buildup duringdry season. There is a large, but short-lived, in-crease at the beginning of the rainy season, anda rapid decrease during the rest of the rainyseason because of leaching.

Since the level of plant-available nitrogen inmany tropical soils is low, the use of extra ni-trogen (green manure, animal waste, or fertil-izer) will almost always increase yields of cropsif these crops can make use of the extra nitro-gen. Therefore, if nitrogen fertilizer is to be ad-ded, it should be at rates that can be justifiedeconomically.

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Since most nitrogen fertilizer is very transi-tory due to its soluble nature, the use of nitro-gen should be timed to the needs of the plant,This will avoid excessive loss due to leachingrain or denitrification, the loss of nitrogen asa gas. Numerous experiments in both temper-ate and tropical climates have shown that theapplication of nitrogen soon after planting,when demand is highest, will result in higheryields and more efficient use of the applied ni-trogen,

Nitrogen loss is not a serious problem withorganic nitrogen from legumes or animal wastesince these complex organic materials are not

subject to leaching like the more soluble inor-ganic fertilizers. This suggests that organicforms of nitrogen have a greater efficiency inhigh rainfall areas. In some cases, nitrogen ad-dition alone will not increase productivity sub-stantially because other elements may be defi-cient or toxic. This is the case with acid soils,Lime will promote legume establishment andgrowth by reducing aluminum availability andincreasing the availability of phosphorus. Phos-phorus deficiency is a serious problem in manytropical soils and must be considered in the fer-tility regime,

PHOSPHORUS

Following water and nitrogen, phosphorusis probably the most limiting nutrient in theTropics. This is particularly true in the acidsoils of the humid tropics since the high alu-minum and iron concentrations render phos-phorus unavailable to plants. The term used todenote this is phosphorus fixation. When phos-phorus is added as soluble monocalcium phos-phate (Ca(H2C9PO4)2) the soil pH is reduced to1 to 1.5 (very acid). The acid dissolves alumi-num, iron, potassium, and magnesium com-pounds and unsoluble phosphates of iron andaluminum are formed. The higher the phospho-rus-fixing capacity of the soil, the higher thecontent of iron and aluminum oxides (56).Higher exchangeable aluminum also increasesthe soil’s phosphorus fixation ability. Becauseof the fixation process, higher rates of phos-

phorus must be added to achieve the same levelof plant-available phosphorus compared to asoil that does not fix phosphorus. The amountof phosphorus added to a soil to get 0,2 ppmphosphorus (adequate level) in the soil solutioncan vary from 20 to 30 pounds per acre to asmuch as 1,500 pounds per acre. A general rec-ommendation for corn and rice in Latin Amer-ica is 100 to 150 of kg P2O5 per hectare for cornand from O to 60 kg for upland rice. In manycases, soils respond only slightly to phospho-rus unless they are first limed (15). In an ex-periment, limed corn plots showed a markedresponse to 50 kg P2O5 per hectare with a yieldincrease from 0.8 to 3.2 tons per hectare. Inlimed plots, rice did not respond to phos-phorus.

MANAGEMENT OF PHOSPHORUS FERTILIZER

Phosphorus responses are common in many In soils with high phosphorus fixation capac-tropical soils. Well-calibrated soil tests can ity, economically sound phosphorus manage-identify the soils with a high probability of ment involves several approaches (56). Twophosphorus response. Phosphorus manage- general approaches are used to deal with highment in soils with moderate fixation capacity phosphorus fixing soils. One is to apply smallis usually a simple procedure: small annual to moderate amounts in bands near the plant.rates of superphosphate can be broadcast The other is to apply a large amount at one time(spread over top of soil) and incorporated or saturating the soil’s fixation capacity, eliminat-banded (placed in a band near the seed). ing the problem right away. However, this has

38-846 0 - 85 - 9

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a disadvantage because it requires a high ini-tial investment and adequate financing. In ahigh-fixing soil from North Carolina, Kamprath(41) studied the residual effect of massive ini-tial applications versus small annual mainte-nance rates applied in bands. In that study, thesmall annual banded application is superior tothe massive single dose.

Applying phosphorus fertilizers in bands isa simple practice that satisfies the phosphorusfixation capacity of a small soil volume, mak-ing the fertilizer directly available to plants. Inusing a system of minimal inputs, banding isvery appropriate since the goal is to increasecrop production with minimal inputs withoutchanging the inherent fertility of the entire soil

volume. Sanchez (56) cites an example ofbanded versus broadcast applications in a highphosphorus-fixing soil in Brazil. The resultsshowed that broadcast-incorporated applica-tions were superior to banded applications inthe first crop. Banded applications concen-trated corn root development around the band.When a temporary drought struck, these plantssuffered more than those of the broadcast plotsbecause those had a more extensive root sys-tem. In time, however, the effectiveness of thebanded treatments increased while the broad-cast treatments decreased. Annually bandedtreatments begantreatments as thein the soil.

to approach the broadcastphosphorus became mixed

SOURCES OF PHOSPHORUS

Research in temperate regions indicates that application without testing. These are largelyphosphorus fertilizers should have at least 40to 50 percent phosphorus in water-soluble formto ensure an adequate supply at early growthstages (23). Ordinary and triple superphosphateand monoammonium and diammonium phos-phates meet this requirement and can be usedeffectively in soils with low to moderate fixa-tion capacities.

In acid soils that fix large quantities of phos-phorus, application of less soluble phosphorussources such as rock phosphate may be moreeffective and economical than the slightly solu-ble forms. Rock phosphates are more reactivein acid soils and usually cost one-third to one-fifth as much as superphosphate per unit ofphosphorus (56).

The literature on tropical agriculture is fullof research indicating the desirability of high-quality rock phosphate sources over superphos-phate in acid soils (46,4,23) and the poor per-formance of low-citrate-volubility rock phos-phate sources in acid soils (3,50,66). Studies atTVA by Lehr and McClellan (45) indicate thatwhen rock phosphate deposits (North Carolinaand Tunisia) are given an index of 100, rockphosphates with a volubility index of 70 per-cent or greater can be recommended for direct

concentrated in North Africa, the Soviet ‘Un-ion, and the Southeastern United States.

The effects of rock phosphates of varying ci-trate volubility on flooded rice yields in an acidsulfate soil from Thailand was studied by En-glestad, et al. (24). The initial and residual ef-fects of the rock phosphates were highly de-pendent on their absolute citrate solubilities.The yield responses of the North Carolina andFlorida rocks approximated those of triple su-perphosphate.

In the Tropics, high-citrate volubility depos-its are limited to relatively small areas in Peruand India (56). The majority of the deposits inmost tropical areas, including significant onesin Brazil, Colombia, Venezuela, Togo, and In-dia have relative solubilities lower than 40 per-cent. Most are unsuitable for direct applica-tions, but their reactivity can be increased byfine grinding or by thermal alteration and fu-sion with silica sand, sodium, or magnesiumcarbonates. These silicophosphates, called“Rhenenia” or thermophosphates, appear tohave promise for acid soils that fix large quan-tities of phosphorus because of the blocking ef-fect of silicon on phosphorus fixation sites(52,27).

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The potential effectiveness of these cheaperforms of phosphorus in acid soils is illustratedin the following table:

Behavior of Different Fertilizer Sources onWheat Grown in Oxisols of Southern Brazil

Phosphorus Relative yieldsource 5-year averageNo phosphorus . . . . . . . . . . . . . . . . . . . . . 100Olinda rock phosphate* . . . . . . . . . . . . . . 179Simple superphosphate . . . . . . . . . . . . . . 206Thermophosphate. . . . . . . . . . . . . . . . . . . . 218

‘Low citrate solubility.

SOURCE W.J. Goedert (personal communication) as cited by Sanchez (1976),

The low citrate volubility Olinda rock phos-phate was inferior to ordinary superphosphate;but when thermally treated with silicates andcarbonates to produce a thermophosphate, itseffectiveness was superior to that of ordinarysuperphosphate. In view of the substantiallylower costs of the rock phosphates and somethermophosphates, both seem desirable alter-natives for soils with high fixation capacities.

An additional strategy, sometimes feasiblefor managing soils with high phosphorus fix-ation capacities, is to reduce their fixationthrough amendments that will block some ofthe fixing sites in the soil. This can be accom-plished in some soils through liming or silicateadditions (56).

Liming soils to pH 5.5 generally increases theavailability of phosphorus by precipitating ex-changeable aluminum and hydroxy aluminum.

This has also been observed by Fox, et al. (29),in high fixing Hawaiian soils.

Applications of silicon or sand (an unessen-tial element), usually as calcium silicate, sodi-um silicate, or basic slag, are known to de-crease phosphorus fixation and increase phos-phorus uptake by crops. In one study, grassyields increased from 2 to 7.6 tons per hectareand phosphorus uptake rose from 4 to 15 kgphosphorus per hectare when 1 ton of siliconper hectare was applied without added phos-phorus (62),

Silicon is generally not considered to be es-sential to plant growth, however, positive yieldresponses have been achieved on highly leachedsoils of the Tropics under intense cultivationof sugarcane or rice. Soils having low contentsof soluble silicon are most likely to show re-sponse to silicon applications. Fox, et al. (32),suggested that the critical level is 0.9 ppm sili-con in water extracts. Responses have been ob-tained on the leached soils of Hawaii, Mauri-tuis, and the rice soils in Japan, Korea, and SriLanka,

In these rice soils, silicon applications in-creased yields because of a more erect leaf hab-it, greater tolerance against insects and diseaseattacks, lower uptake of iron and manganesewhen present in toxicsoil, and perhaps a riseof rice roots.

SULFUR Deficiency

An element with plant requirements very found in sub-Saharan

concentrations in thein the oxidizing power

Africa and the sandysimilar to phosphorus is sulfur. Sulfur defi-ciency results in a reduction of growth and pro-tein deficiency, often resembling nitrogen defi-ciency. widespread sulfur deficiencies andresponses have been reported all over the Trop-ics. McClung, et al. (48), observed sulfur re-sponses in the Brazilian Cerrado in both sa-vannas and recently cleared forests. In CentralAmerica, sulfur deficiencies are also wide-spread (5 I ,28), Sulfur deficiency has also been

soils of central Africa (8). They have been re-ported in Asia (52) and in Australia and Ha-waii (68,30). Sulfur-deficient soils are generallyhigh in allophane or oxides, low in organicmatter, and often sandy. Soils subject to re-peated annual burning are often sulfur defi-cient since about 74 percent of the sulfur isvolatilized (goes off as a gas) by fire. Sulfur-deficient soils occur in unpolluted, inland areaswhere the atmosphere is low in sulfur.

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Sulfur requirements are similar to phospho-rus in tropical conditions ranging from 0.1 to0.3 percent of plant tissue. A sulfur deficiencyat early growth stages may disappear laterwhen the roots come in contact with the sulfur-bearing subsoil.

POTASSIUM

The last major element to be considered, ofless importance than the other nutrients con-sidered here, is potassium. Potassium deficien-cies do occur in the Tropics, however, lack ofpotassium is not nearly as widespread as ni-trogen and phosphorus deficiencies. Boyer (10)in a review article suggests that the absoluteminimum requirement of exchangeable potas-sium—the amount considered to be availableto the plant—is close to 0.10 meq/100 g of soilbut that this may vary between 0.07 and 0.20meq/l00 g depending on the kind of cropsgrown and the soils.

In Africa, the most severe potassium defi-ciency appears in the savanna on sandy soils.In the lower Ivory Coast, potassium applica-tion resulted in very substantial yield increase

In general, small rates of sulfur (10 to 40kg/ha) will overcome sulfur deficiencies. Sul-fur as part of either nitrogen or phosphorus fer-tilizer is usually sufficient to take care of sul-fur problems. If not, any soluble sourcecontaining sulfate will work.

DEFICIENCY

with oil palm (9). Potassium deficiencies haveoccurred in the southwestern Cameroon (64)in Madagascar (65) and in Brazil on sandy soils.Laudelot (45) in the Congo (Zaire) showed thatthe exchangeable potassium increased from0.067 meq/100 g to 0.325 meq/100 after burn-ing a forest. Thus, clearing a forest by burn-ing substantially increases the potassium con-tent of soils. Busch (12) found that the increasesin bases (calcium, magnesium, and potassium)persists for a number of years after burning.

When soils are potassium deficient, fertili-zation with moderate amounts of potassiumusually corrects the problem. High yield cropsthat contain high carbohydrates such as pota-toes have a higher potassium requirement thana grain crop such as wheat or rice.

RICE

Since rice culture differs from other cropsbecause it demands flooding, it must be con-sidered separately. Regardless of their originalpH values, most rice soils reach a pH of 6.5 to7.2 within a month after flooding and remainat that level until dried (56). This increase insoil pH is a result of the release of OH. (base)ion when Fe(OH)3 is reduced. Consequently,liming is of little value in flooded rice produc-tion. If low pH is a problem, flooding 2 to 3weeks prior to transplanting may eliminate thisdanger.

Oxygen is consumed in flooded soils; there-fore, nitrates will be lost via denitrification.Since ammonium is already reduced, it is sta-ble in flooded environments. Organic matterdecomposition proceeds at a slower rate with-

out oxygen, however, materials such as ricestraw (which has a high carbon to nitrogen ra-tio) may mineralize more rapidly under theseanaerobic conditions, thus providing a sourceof plant-available nitrogen. Soil solution phos-phorus increases upon flooding, explainingwhy additional phosphorus in flooded condi-tions is rarely needed.

Nitrogen use in rice is very critical. An am-monium source is generally used when fertil-izer is used. It is incorporated in the soil be-fore seeding or transplanting, or broadcast atdifferent stages of growth. Incorporations of2 inches are usually sufficient for constantflooding conditions. This places the nitrogenbelow the oxidized layer, a necessary condi-tion to prevent denitrifiction (49). Nitrogen up-

219

take proceeds throughout the growth cycle ofthe rice plant but it is particularly critical dur-ing two physiological stages: at the beginningof tillering and at the panicle (grain head) ini-tiation stage (47). Adequate nitrogen at tiller-ing increases tillers, which is closely correlatedwith yield in short varieties. However, exces-sive nitrogen after maximum tillering and be-fore panicle initiation may result in a large pro-portion of unproductive tillers and prematurelodging in tall varieties. Excessive nitrogen af-ter flowering may extend growth duration andincrease susceptibility to some diseases.

The efficient use of nitrogen is very impor-tant economically. Scientists at the Internation-al Rice Research Institute (38) have almost dou-bled the efficiency of nitrogen fertilizer byeither mixing it in mudballs or making urea bri-quettes. Fifty pounds of nitrogen per acre inthis fashion was equal to 100 pounds per acreapplied on the surface.

Rice rarely responds to phosphorus fertilizerexcept in highly weathered leached soils (57).Traditional soil tests for phosphorus do a poorjob in predicting the need for phosphorus un-der flooded conditions.

Zinc deficiency is probably the most wide-spread micronutrient disorder in tropical rice,occurring in parts of India, Pakistan, the Philip-pines, and Colombia under low lowland con-ditions (63,69,15,39). It also occurs throughoutthe Cerrado of Brazil under upland conditions(19). In lowland rice, zinc deficiency is asso-ciated with calcareous (high base) soils and isaccentuated by prolonged flooding. Deficiencycan be corrected by applications of 5 to 15 kgof zinc per hectare as the sulfate or oxide in-corporated into soil before seeding (35). An al-ternative is dipping the transplant seedlings ina 1 percent zinc oxide suspension before trans-planting and mixing zinc oxide with pre-soakedrice seeds before direct seeding (69,15). Yieldincrease of 2 to 3 tons/ha have been achievedwith 1 to 2 kg of zinc oxide per hectare (11).This again is an example of fertilizing the plantand not the soil, a much more economical andeasy approach than treating the whole soil.

Potassium deficiency is rare in lowland riceas these soils are usually adequate in exchange-able potassium and receive potassium in theirrigation water when flooded. Soil tests aregood for estimating potassium-deficient soils(56).

PLANTS THAT TOLERATE ADVERSE CONDITIONS

Up to this point this paper has concentratedon soil modification as a way to increase cropproduction. Another approach is to select orbreed crops that will tolerate and produce wellunder natural, though sometimes hostile, con-ditions,

Certain crops grown exclusively in the Trop-ics normally grow at pH levels that would killcorn or soybeans (56). Pineapple is perhaps thebest known example, but coffee, tea, rubber,and cassava also tolerate very high levels of ex-changeable aluminum. Among the pasture spe-cies, several grasses and legumes are apparent-ly very well adapted to acid soil conditions,Tropical grasses such as guinea grass, Panicummaximum; jaragua, Hyparrhanea rufa; molas-

ses grass, Melinia multiflora, and several spe-cies of the genera Paspalum and Brachiariagrow well in very acid soils.

Legumes are considered very susceptible tosoil acidity because of their high calcium re-quirements for modulation. However, severaltropical pasture legumes are strikingly welladapted to acid conditions. Stylosanthes spp.,Desmodium spp., Centrosema spp., Calopogo-nium spp., and tropical Kudzu, Pueraria phase-oloides are the principal ones (56), Among thegrain legumes, cowpeas and pigeon peas aremore tolerant of acidity than field beans andsoybeans. Many of these species have evolvedin acid soils and have genetic properties thattolerate conditions associated with high alumi-num levels.

220

On the basis of research, Spain, et al. (61),have produced a list of species adapted to highsoil acidity and aluminum:

Crops and Pasture Species Suitable forAcid Soils With Minimum Lime Requirements

Lime Al Cropsrequirement saturation (using tolerant

(tons/ha) (percent) pH varieties0.25 to 0.5 68 to 75 4.5 to 4.7 Upland rice, cassava, man-

go, cashew, citrus, pine-apple, Stylosanthes,Desmodium, kudzu,Centrosema, molasses,grass, jaragua, Brichiar-ia decumbens, Paspalumplicatulum

0.5 to 1.0 45 to 58 4.7 to 5.0 Cowpeas, plantains1.0 to 2.0 31 to 45 5.0 to 5.3 Corn, black beans

In a review of tolerance to aluminum, Foy(1974) concluded:

1.

2.

3.

4.

5.

6.

Some aluminum-tolerant varieties keep de-veloping and are not injured.Some aluminum-tolerant varieties increasethe pH of growth medium which reducesthe availability of aluminum; sensitiveones decrease soil pH, compounding theproblem.Some tolerant species accumulate alumi-num in their roots or translocate (trans-port) aluminum at a slower rate to the top.Aluminum in roots does not inhibit the up-take and translocation of calcium, magne-sium, and potassium in tolerant varieties,whereas it does so in sensitive varieties.High plant silicon is associated with alu-minum tolerance in certain rice varieties.Aluminum tolerant varieties do not inhibitphosphorus uptake and translocation asmuch as susceptible varieties or species.Also, many aluminum-tolerant species orvarieties are very tolerant of low phospho-rus levels.

Cassava Manihot spp., a tropical root cropgrowing widely on infertile soils that are fre-quently acid, has acquired the reputation forbeing a crop that yields well under very lowfertility conditions (17). Cassava tolerates lowsoil pH and high levels of aluminum and man-ganese as well as low levels of soil calcium, ni-trogen, and potassium better than many other

species. While it has a high phosphorus re-quirement for maximum growth, it can usephosphorus sources that are relatively unavail-able to other plants. It is highly tolerant of un-certain rainfall patterns and is an extremely ef-ficient carbohydrate source on low fertility,acid soils with low levels of fertilizer applica-tions. Cassava yields of 36 metric tons per hec-tare per year have been obtained under condi-tions that are suboptimal for many crops.

An estimated 1.57 million people live in theTropics and this number is likely to expand to5 billion in 50 years (55). This rapidly growingpopulation will have to rely increasingly onplants as sources of both energy and protein.In the semiarid to subhumid climates, two-thirds of dietary calories come from cereals,while in the humid tropics the bulk of dietarycarbohydrate comes from roots and tubers. Theproduction of starchy root and tuber crops isinherently more efficient than the productionof cereals, especially on marginal lands and/orland with minimal external inputs. It is esti-mated that with roots and tubers, at least twoto three times more caloric energy can be pro-duced per unit of land and time and with onlyone-third to one-half the production cost ofcereals. It is, therefore, suggested that an in-creasing proportion of human energy needswill be derived from starch roots and tubers.The Tropics have a large amount of infertilelands, ill-suited for many crops with moderateto high nutrient requirements. One of the mostserious problems of some tropical soils is phos-phorus deficiency that seriously limits cropproduction.

Sweet potatoes (Ipomoea batatas (L.) Lam.),long associated with poor people and less pro-ductive soils, may be one solution (54). Thereis good reason that the sweet potato is grownso widely under such difficult conditions.Sweet potato had one of the lowest phosphorusrequirements of the crops studied (Lettuce,Lactuca sativa; corn, Zea mays; and Chinesecabbage, Brassica pekinesis) (31).

The International Rice Research Institute(39), classified varieties of rice that are toler-ant or sensitive to low phosphorus. They are

221

also selecting varieties for tolerance to iron de-ficiency or toxicity and the presence of toxicsoil reduction products.

In summary, it is apparent that high produc-tion can be achieved on rather hostile soils aslong as tolerant species or varieties of plantsare selected, This would be a strategy that re-lies on no or minimal inputs and yet can in-crease food production substantially,

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6.

7.

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9.

10.

11.

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. ., “- ,- ---

Chapter XII

The Gene Revolution:Maximizing Yields in the

Tropical Moist Forest Biome

James A. DukeU.S. Department of Agriculture

Beltsville, MD 20705

Contents

Page

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227Economic Botany Laboratory ...,. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229The Quest for Tolerant Germplasm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230Intercropping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230Legumes. ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231Azolla as Fertilizer. , . . . . . . . . . . . . . ,....., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232Heat or Meat... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233Sewage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234Oil Seeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235Allelopathy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236Drug Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236Essential Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237Fiber Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237Gums, Resins, and Balsams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237Rubber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238Wax Crops. ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,..., . . . . . . . . . . . . . . . . 238Weeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239Tropical Moist Forest Biomass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

References, . . . ., ......,, ,...., . . . . . . . . . . . . . . . . . . . . ...,, . . . . . . . . . . . . . . 242Appendix A–Magic Mountain: 2000 AD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,. 243

List of Tables

Table No. Pagel. Estimates of Net Primary Production in Tropical Forests. . . . . . . . , . . . . . . . . . . . 2402. Tropical Root Crops, .....,, ,, .,..,, ., . . . , , , ..., , , , ., . . . . . . . . . . . . . . . . . . . 2403, Tropical Vegetables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2404. Tropical Spices, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2415. Net Primary Productivity . . .+.,.. . . . . . . . . . . . . . . . ..,+. . . . . . . . . . . . . . . . . . . . 241

Chapter XII

The Gene Revolution:Maximizing Yields in the

Tropical Moist Forest Biome

It is the skills of plant geneticists, rather than record after another in crop yields in , . . bothlarge amounts of artificial additives such as temperate and tropical zones (Norman Meyers,pesticides and fertilizers, that have led to one The Sinking Art, 1980).

Should there be a Gene Revolution, based onlow-input multiuse extensive agroecosystems,to supplant the Green Revolution, based onhigh input intensive agriculture? Genes bestadapted to the marginal environments foundin the humid tropics should be pooled, com-bined, and recombined to produce moderate-yielding, well-adapted, multipurpose species.These gene combinations and recombinationshould be tested, not for their yields in mono-cultural situations, but in well-planned, multi-tiered intercropped agroecosystems.

The search for appropriate genes can bescientifically directed by a computerized cat-alog of the varieties, cultivars, and species ofpotentially economic native and introducedspecies. Technologies that would be part ofsuch a multiple-use agroecosystem would in-

clude small-scale biomass- and alcohol-fueledand solar plant-extraction equipment, as wellas fermentation and distilling apparatus, de-signed to run on some of the products of theagroecosystem. In summary, the Gene Revo-lution should be directed toward a multitiered,multiuse, polygenic, low-input agroecosystem,fueled and fertilized from within. The GeneRevolution should pull together the five majoringredients important in marginal environ-ments: 1) tolerant germplasm, 2) multiple andintercropping scenarios, 3) organic gardening(recycling animal and plant residues), 4) bio-logical control of pests (including allelopathy),and 5) whole plant fractionation and utilizationfor such integrated agroecosystems. Such sys-tems should be developed from existing farms,not from the forests.

INTRODUCTION

... Plant germplasm can be selected and su- long periods without a high level of inputs. Butperior cultivars developed on the basis of their such inputs are rarely affordable to develop-adaptation to problem soils. Although we have ing tropical countries. If these countries can-moved slowly to capitalize on this information, not afford the inputs required for high-levelit offers great promise in reducing energy in- production of conventional food crops, per-puts and improving the reliability of crop haps they should aim instead for a moderateyields in both developed and developing coun-tries (A. A. Hanson, 1976). production of nonconventional crops with

moderate inputs. The Green Revolution, whichThe highly weathered soils of the humid trop- called for maximum inputs, has pretty well run

ics will rarely support conventional crops for its course, maximizing productivity where high

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inputs are possible. It is time for the Gene Rev-olution, to tailor existing plant types to max-imize output with minimal input. The genes ex-ist in nature, but they are disappearing fast. Itis up to the Gene Revolutionists to get the genestogether in the most meaningful manner, tomaximize productivity under various low in-put scenarios.

With the end of the cheap energy era, devel-oped and developing countries must reassesstheir imports and exports, their agricultural in-puts and outputs, and their needs, often witha view toward substituting botanochemicalfibers, fuels, and pharmaceuticals for thosederived from petrochemicals.

Energy-hungry developing countries shouldclosely watch developments at the NorthernRegional Research Laboratory in Peoria, Il-linois. If the botanochemical approach is prac-tical today or tomorrow in an energy-rich coun-try like the United States, then it will be all themore practical in the energy-poor countries ofthe humid tropics because:

1. Natural (and agricultural) productivity perunit area is higher in tropical than tem-perate zones, other things being equal.Hence, there should be much more bio-mass for a total-utilization scheme. TheGene Revolutionist is charged with find-ing the best genes and combining them inthe best plants for maximizing output inthe marginal low-input farm scenario.

2. The diversity of useful species on whichto draw for our total-utilization concept isperhaps 10 times as high in the Tropics asin the temperate zone. Hence, the array ofcombinations for the recommended inter-cropping approach is staggeringly com-plex. The multitiered, intercropping agro-ecosystem being studied seems to be oneof the most highly productive terrestrialagroecosystems, competing with the highlyproductive aquatic ecosystems of the Trop-ics. Yields of either of these systems canbe improved vastly by the addition of ame-liorated sewage sludge or other natural fer-tilizers in lieu of artificial fertilizer inputs.However, sewage sludge is recommended

for biomass and chemurgic crops, not foodcrops.

In this talk, I will try to respond to the cen-tral issue: the highly weathered soils of the hot,wet tropics. These soils are rich in aluminum,silica, and iron, and poor in the common plantnutrients. What could USDA’s EconomicBotany Laboratory (EBL) do to improve “bio-logical productivity of such soils without usingmuch or any chemical fertilizer?” That is thecharge put to me by the Office of TechnologyAssessment. Let’s analyze that a bit before pro-ceeding. Is it rare that we can improve natu-ral biological productivity? Nature does a goodjob maximizing biological productivity undernature’s constraints. If I compared produc-tivity, I would only be comparing usable withtotal productivity. And if we are talking aboutthe maximum Usability Concept, then we arenot talking conventional agriculture at all.

Before laying out my plans for any country,I would analyze their import tables, especiallythe energy columns. Then I would plan amultitiered agroecosystem that would max-imize benefits to the countries, import-exportsituation, seeking the best genes to maximizeoutput for a modicum of inputs, under theecological conditions prevailing. Geneticistscould maximize the yields while Americantechnology could maximize the extraction ofuseful products from the total yield.

Humid tropics has been variously defined.Most of my examples relate to what is calledthe Tropical Moist Forest (TMF), where annualbiotemperatures are greater than 24° C and an-nual rainfall is between 2,000 and 4,000 mm.I have spent years in the Tropical Moist Forestsof Latin America, and am still awed by thediversity of economic products endemic to thearea. There are even more exogenous eco-nomic species from similar ecological zonesoutside Latin America. Unlike others in thisworkshop, I do not stress using native species,but I share the belief that we should not intro-duce exotics that are ill-adapted to an area.EBL’s computer system helps find the rightgermplasm for a given tropical ecosystem.

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Drawing on these tropical gene pools, theGene Revolutionist has perhaps more than 75percent of the world’s species to consider, per-haps 250,000 species. Each is a unique chemi-cal factory, manufacturing biomass that wemay need to draw upon as a source of energy.As the preface of the National Research Coun-cil’s book, Conversion of Tropical MoistForests, begins: “The tropical moist forestbiome is biologically the richest, and least wellknown portion of the earth’s surface.”

Unfortunately, much of TMF is underlain byfemalsols (strongly weathered soils of tropicalregions, consisting mainly of kaolinite, quartz,and hydrated oxides, and having a low base ex-change capacity). Dudal (6) summarizes themineral stress phenomena in such soils:

1. Deficiency in bases (Ca, Mg, K) and in-capability to retain bases applied as fer-tilizers or amendments.

2. Presence (pH < 5.2) of exchangeable Al,toxic to many species and active in bind-ing phosphates.

3.4.5.

6.

Presence (acid soils) of free Mn, also toxic.Fixation of phosphateDeficiency of molybdenum, especially forlegumes.Fe and Mn toxicity shown by paddy rice.

Such soils are said to occupy more than a bil-lion hectares, more than 8 percent of theworld’s soil.

There are those who say that conversion ofTMF to agriculture will lead only to the so-called “red desert. ” Ewel (8) says, however:

The red desert view of mature tropical eco-system destruction is incorrect. Nature abhorsa vacuum, so sites laid bare by human activ-ity are quickly covered by some kind of com-munity, although not usually the original one.We must face the fact that successional com-munities are going to be the dominant tropi-cal ecosystems of the future.

ECONOMIC BOTANY LABORATORY

I am still awed by the diversity of the Tropi-cal Moist Forest. Working at the EconomicBotany Laboratory, I have begun to try toorganize the information pertinent to the Trop-ical Moist Forest. There is already so much in-formation that we depend on computers toassimilate the information. We are primarilyconcerned with the medicinal plants of theworld, especially those with anticancer activ-ity. secondly, we are concerned with catalog-ing agronomic, ecological, geographical, andutilitarian information on economic plants ofany description. From his studies alone,Schultes (23) compiled a list of more than 1,300species employed by natives of the northwestAmazon as medicines, poisons, or narcotics.Our computer files already contain entries onmore than 4,000 folk medicinal species, someof which double as food plants, fiber plants,dye plants, etc. We have yield data on some ofthese, under various ecological regimes in theTropical Moist Forest.

With careful expansion, such a data basecould catalog information on ecology, utility,and yields of all economic plants, and guidethe Gene Revolutionists in their search for theright genes or germplasm. Details of some strat-egies that should be employed in the quest oftolerant germplasm are explored in Duke (7).Ecological data on more than 500 species suit-able for exploitation in the Tropical Moist For-est are tabulated. I will not relate all those datahere, but will present a few examples.

We know the conventional yield figures foronly a fraction of tropical crops. Biomass orresidue figures are even rarer, although suchnumbers are necessary for systems analysis ofthe yield potential of a multiuse agroecosystern.According to Westlake (29), conversion factorsrange from 1.3 to 4.0 for estimating aerialbiomass from conventional yield units. I calledall the experts I could find, in vain, in mysearch for the biomass figures for the temperate

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lentil. Who would I call for such figures on themyriads of tropical products? The numbers donot exist. “The accuracy of productivity meas-urements is the lowest for tropical areas. Thekey to future refinement of our understandingthe global productivity capacity lies, therefore,in the study of tropical primary productivity”(16). If biomass is a viable competitor in theenergy field, it is time pertinent numbers weregenerated by baseline research program.

If I were Secretary of State, determiningwhat strings were tied to AID funds overseas,I would see to it that funds went to carefullydistributed research plots in developing coun-tries. These plots would be funded to generatethe numbers needed to support Maximum Uti-lization Concepts. How much biomass can wegrow and harvest under various scenarios?Which scenario gives us the greatest net usablereturns? I would fund no studies that did notgive biomass yields related to climatic andedaphic data, and I would fund no country that

did not make a commitment to preserve theircurrent forests, and concentrate on increasingthe productivity of current croplands.

Why should the remaining forests not be con-verted into agroecosystems? If they are lost,thousands of undescribed species will disap-pear forever before they have been named.Thousands of others will disappear with nostudies of their economic potential. It is diffi-cult to put a price on their heads. One in tenspecies studied shows anticancer activity; butonly about 15 of the first 30,000 species stud-ied in our anticancer program are of sufficientinterest to have reached preclinical testing.Only one of those has resulted in thousands ofremissions in cancer. This superstar, Catharan-thus roseus, the Madagascar periwinkle, is apantropical ornamental and folk medicine inTropical Moist and Dry Forests. There areprobably nine more superstars awaiting discov-ery (if they do not fall victim to the tropicalaxe). Can we afford to extinguish them?

THE QUEST FOR TOLERANT GERMPLASM

Elsewhere, I have advocated and outlined is cheaper to increase yields by finding ameasures for seeking out the genes we need for cultivar that will tolerate the acidity, and itsmarginal environments in the Tropics (7). complications, than to increase the yields byOther research backs this idea: importing 6 tons of lime per acre. This is just

The correction of Al and Mn toxicities by the first step in the Gene Revolution. Incor-

liming is not always economically feasible, porating the appropriate genetically tailored

especially Al toxicity in strongly acid subsoils. species, varieties, races, and cultivars in aHowever, plant species and varieties with spe- multitiered, multiple cropping system requirescies differ widely in their tolerance to both even further genetic selection, manipulation,factors, and some of these differences are and experimentation.genetically controlled (10,25).

It is such differences we hope to capitalize onin the EBL Quest for Tolerant Germplasm. It

INTERCROPPING

Work on multitiered agroecosystems is pro- trees, are common. Thousands of combinationsceeding most rapidly in Asia, but temperate are possible in a tropical three-tiered system.systems are familiar to us all. Two-tiered sys- In one, pineapple was planted as the groundtems, with hay, legume, or cereal crops alter- crop, cocoa as the first story, and pepper as thenating or intercropped with rows of fruit or nut second story. Total harvestable crops and

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residues from such systems usually exceed sig-nificantly the expected crops of the individualspecies, had they been planted in monoculture.Advocating agroecosystems that simulate thenatural ecosystem it replaces Hart (12) says:

The replacement of weeds by analogouscrops and an increase in crop diversity willusually reduce the amount of energy used byweeds and pests.

Those systems of tropical forestry and agri-culture that have been successfully employedfor the longest periods are those that favor themaintenance of large mycorrhizal fungus pop-ulation. Traditional shifting agriculture in

small forest-enclosed plots probably attainsmycorrhizal homeostasis. Mycorrhizae seemto minimize the expense to the host of seeking-out minerals. Cultivation of annual crops maylead to increased prominence of nonmycor-rhizal species and grasses in weed communi-ties. Soil sterilization can eliminate mycor-rhizal fungi, and fungicides used againstpathogens may adversely affect mycorrhizalfungi as well. Monoculture of crops that areprobably nonmycorrhizal, such as grain ama-ranths and chenopods, might markedly lowermycorrhizal fungus populations and jeopard-ize subsequent mycotrophic crops (14).

LEGUMES

Even the nitrogen fixed by legumes is notfree. Under conventional farming, there is aprice to pay for the nitrogen contribution ofthe legume. In an unpublished paper, I pulled,at random, biomass yields for pure stands ofC-4 grasses, C-3 grasses, and legumes. Thoughrelatively higher in nitrogen and protein, thelegumes yielded only half as much total bio-mass as the C-3 grasses, which in turn yieldedonly about half as much total biomass as theC-4 grasses. These are the biological costs (1)for nitrogen fixation and (2) excessive photo-respiration. Although no one seems to have ac-cepted my simple 1:2:4 ratio, I believe it. Socalled super-yield targets in the United Statesare 100 bushels of soybeans; the target for cornis 400 bushels.

Appropriate combinations of legumes andgrasses seem to give the best yields for forageor hay, and probably for maximum utilizablebiomass under renewable situations wherewater is not the limiting factor. The C-4 grassmight give highest yields for a while, but itseems doubtful that such yields would be sus-tainable without the help of added N, be it fromlegume, crop residues, manure (green orbrown), or sewage sludge. For high-quality leafprotein, the legume seems indispensable formost scenarios (without the sewage increment)whether the protein is for animal food, humanfood, or chemurgic use.

The amount of N fixed by legumes varies ofcourse, but some of our economic legumes playa larger role than making beans and fixing ni-trogen. According to Nigmator, et al. (1978),the cultivation of the legume licorice (Glycyr-rhiza glabra) showed a marked ameliorative ef-fect on saline soil in Uzbekistan, Russia. Thelicorice, in pure stands, did not form a com-plete soil cover during the first 1 to 2 years, butthis was achieved by sowing it in mixture withsudan grass, cowpea, and lablab. The mixturedecreased the evaporation and the rise of saltsto the upper soil layers. Haines, et al. (11), re-ported that undersowing sycamore (Platanusoccidentals) with clovers and vetch in a dis-cultivated, z-year-old plantation suppressedweed growth to the point where height and vol-ume increments of the young trees were in-creased significantly.

According to Felker (9):

Leguminous trees have a unique advantageover annual legumes in dealing with the in-hibitory effect of drought stress on nitrogenfixation because the deep-rooted leguminoustrees may reach moisture, and thus relieve theplant of water stress for a longer time in theyear than is possible with annuals.

An illustration of the ability of leguminoustrees in semiarid climates to increase soil fer-tility more than annual legumes can be found

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in West Africa, where yields of peanuts are in-creased if grown beneath Acacia albida trees.

The work on “teaching the grasses to fix ni-trogen” goes on, but does not generate as manyheadlines as in the past. Nitrogen-fixation isbeing reported in more and more nonlegumes.Just this month, I noted an abstract dealing

with nitrogen fixation in blackberries. Becking(z) assayed nitrogenase activity by acetylenereduction in detached Rubus ellipticus rootnodules. It was similar to that in several non-legume N2 fixing nodules. The endophyte wasan actinomycete.

AZOLLA AS FERTILIZER

While legumes are one source of fertilizer forour multitiered agroforestry units, tropicalazollas might be another. Azolla, an aquaticfern, is a source of nitrogen. Clark (5), review-ing Azolla use in China, notes that Azolla“seed” are started in nurseries, then the seedferns are introduced directly into rice paddies.In some areas, two rows of rice are plantedwith the Azolla growing in larger rows on ei-ther side of the double rice rows. Yields of 15MT/ha of rice and 150 MT of Azolla have beenreported for this simultaneous cultivationmethod. Rice grown with conventional fer-tilizers averages only 10 MT/ha (5). No men-tion is made of fish biomass harvested fromsuch ecosystems. Could they also harvest 15MT/ha catfish as have been reported from well-aerated Louisiana fishponds (21)? Grass carp(Ctenopharyngodon idella) and Tilapia mossam-bica are said to relish azolla, which has alsobeen fed to cattle, chickens, ducks, and evenhas been suggested for human consumption.Typically, yields of grass carp are 10 timeshigher in the Tropics (l,500 kg/ha) than in thetemperate zone (164 kg/ha).

Unfortunately, we do not know that Clark’s150 MT of Azolla is dry weight or wet weight;if dry weight, we have our fertilizer factory pro-ducing biomass equivalent to some of the high-est reported, while increasing the yields of therice crop, almost incredible. Here let me pointout serious conflicts facing USDA officials:there are potent advocates and opponents ofthe introduction of many of the biomasswonders of the world (Acacia, Azolla, Leu-caena, Prosopis, etc.) and the opponents hope

that the advocates are willing to foot the billshould these wonders become the major weedof the 21st century.

I mention Azolla first because it is beingchampioned as a free fertilizer, one producing150 MT of biomass, while increasing the yieldof rice by I% times. These are the “facts”hailed by the advocates. Azolla pinnata candouble its biomass in 3 to 5 days, maybe 5 to10 days in the field. Some claim that Azolla willsuppress other weeds in rice, if not the riceitself. Other reports indicate the Azolla can ei-ther prevent mosquitoes from laying their eggsof their larvae from surfacing. Some say it re-leases nitrogen while alive, others only afterdeath. Vietnam reports 1 MT/ha N fixed peryear; China 0.7 to 1.8 MT N (13).

But there is a weed potential lurking there.Weeds cost the United States about $16 billionin 1979. Would Azolla introduce increaseyields or would it clutter up more ponds thanit helps. Responsible weed scientists as loudlyand justly proclaim their fears as responsibleforward-lookers champion this “free” fertilizer.There is no cut and dry answer.

On the negative side of the Azolla equation:

● In Japan, there have been complaintsabout Azolla covering the rice seedlings.

● In the Philippines, Azolla is called a weedin rice.

● In New Jersey, it has clogged up waterchannels to boat traffic.

● In South Africa, farmers claim it killedfish, prevented cattle from drinking thewater, and clogged pipes.

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MEAT OR MEAT

The Tropics may not face the heat or meatdecision that temperate countries will face ifthere are no energy breakthroughs soon. Ac-cording to some estimates, more than 90 per-cent of U.S. cereals and legumes are destinedfor animal food. If Americans went vegetariantomorrow, and quit exporting grain, more than95 percent of our agricultural biomass couldgo into ethanol production here. Some of uswould rather be warm and do without meat,than be cold and eat meat regularly; otherswould say an emphatic “no.” According toMeyers (19), much TMF biomass goes intocheap hamburger for the United States. Wouldit be better converted to fuel for the people ofthe TMF?

I have been a human guinea pig on threehuman nutrition studies at USDA, all involv-

ing high fiber and/or vegetarian diets. In one,20 male subjects, none vegetarian or particu-larly sympathetic with vegetarianism, were fedsoy protein in lieu of meat protein. None suf-fered from the soy as opposed to meat. On thecontrary, there were no significant changes inthe health of the subjects, at least by the stand-ards investigated. From 40 to 50 percent of thehuman subjects preferred each soy analog toits meat counterpart.

Thanks to coal, America need not face theheat or meat crisis immediately. Thanks to thetemperature of the humid tropics, the TMFmight not face that choice either. But theymight need to decide whether their biomassresidues go into animal production or fuels fortheir machinery.

WOOD

Even today in the United States, wood is saidto provide more energy than hydroelectric ornuclear power. Wood is a valuable byproductof the multitiered agroecosystem, and the GeneRevolutionist should remember that in tailor-ing species for TMF.

The growth rate of tropical weed trees char-acteristic of the humid lowlands are quiteremarkable. I have measured naturally regen-erated Trema micrantha in Costa Rica’s OSAPeninsula, which were 9 m tall at one year,and more than 30 m tall at 8 years. It is thesefast-growing, low-density trees which willconstitute the wood resource of the future asmature tropical forests are felled and regen-erate (8).

Ewel’s figures for 13-month-old regrowth in va-rious life zones are TWF, 12 MT/ha; TDF, 10

MT/ha; SWF, 6 MT/ha; SDFA, 5 MT/ha; andTropical Montane Rain Forest, 1 MT/ha.

I do not advocate replacement of wood as asource of energy for cooking and heat in theTMF. I do advocate the production of cheapwood-burning devices for distribution to thepoor. Most of the timbers of the Tropics go upin smoke, much of it wasted. With energy-conserving wood stoves, there would be morebiomass available for the production and dis-tillation of alcohol and other uses.

Liquid fuels for use in cars, trucks, andvehicles should be produced by all but thesmallest farms in cheap mass-produced stillsprovided by the technologically well-off,

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SEWAGE

There is justifiable concern that maximumuse will strip the soils of organic matter. If weonly use the above-ground biomass, we leavethe below-ground biomass. According to VanDyne, et al. (28):

Below-ground production is more thantwice above-ground in annual grasslands, butstanding crops of biomass below-groundmaybe five to ten times as much as above--ground standing crops.

The humid tropics do not lack water like thearid tropics, but they do need organic fer-tilizers, especially if continuously harvested.Here I take the opportunity to introduce intothe tropical scenario an idea that I think shouldbe exploited in the United States: pipingsewage sludge out of the cities of the world andinto energy farm areas. The pipeline routescould parallel proposed coal-slurry lines, nat-ural gaslines, or petroleum pipelines. Oil shalemines, strip mines, any type of old mine sitecould be partially or totally reclaimed or im-proved with sludge-planted areas. The highestbiomass yield reports I find are from Thewealth of India, where such yields as 160 MT/ha for Pennisetum purpureum are reported forfields irrigated with sewage. Westlake (29)reports unusually high yields even in the tem-perate zone. With sewage irrigation and inter-cropping, he reported DM yields of mixedalfalfa-orchardgrass at 26 to 39 MT/ha, at leastfive times greater than the expected yield ofalfalfa alone, without sewage irrigation. Thiscompares with 40 MT for Phragmites australis,which Westlake describes as the most produc-tive temperate community.

City planners should adopt the Design WithNature Concept, building above the productivealluvial plains, clearly the most productivelands in any biome, with nothing but naturalinputs. Alluvial plains and energy sumpsshould occupy the fertile lowlands, while no

more building on the floodplains should bepermitted. These most fertile lands are beinggobbled-up by suburban creep, here andelsewhere.

I decry the cancellation of plans to bargesludge to Haiti, because I believe sewage sludgecould play a big role in the greening of Haitior the Sonoran or Negev deserts for that mat-ter. We could concomitantly alleviate the short-age of water and organic matter in the desert,with its low real-estate values, while alleviatingthe waste disposal problem in the cities, withtheir high real-estate values.

Water-borne sludge could prove a boon to thehumid tropics. If sewage sludge can doubleyields in the humid tropics, the reverse pipe-line could be shipping ethanol out, still leav-ing a positive balance in organic matter in thehumid tropics. Once the pipelines were estab-lished, the sludge could be a free input, dou-bling outputs. Hence, I see this untried conceptas one way to double the productivity of thehumid tropics, or treble the productivity of thearid tropics, with a free input. The excessyields could be devoted to production of al-cohol, for internal or external energy use.

Such an area might appropriately be calledan energy sump, and would not be an attrac-tive place to live, but the products of the energysump could make jobs there, and a higherstandard of living elsewhere.

Here, as much as anywhere, the talents of theGene Revolutionists will be called into play.The genes for maximizing productivity in theenergy sump will be very different from thosefor maximizing productivity in the unalteredhumid tropics. Planting, cultivating, weeding,and harvesting technologies, even the recom-mended varieties, if not species, will be dif-ferent for the two scenarios.

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OIL

Back in April 1977, I suggested that palm oilmight someday be competitive with petroleum.Today, foreign palm oil in New York is stillhigher than domestic petroleum at the pump,but at the rate the gap has closed since my pa-per. Palm oil will be as cheap as petroleum bythe year 2000.

Oil palm is one of many species with vari-eties tolerant of the allic soils of the humid trop-ics. Oil palm is currently growing in countriesthat show deficits in both edible oils andenergy. It has already been shown that simplygrowing legumes between the oils palms canincrease oil yields by 2 MT/ha/yr (3) or theequivalent of 6 barrels of oil per hectare, simplyby the selection of proper legume for intercrop-ping. These legumes (Centrosema pubescens,Pueraria phaseoloides), in addition to increas-ing our energy budget, at little or no cost fol-lowing planting, can provide food, conven-tional or unconventional. I am sure, based ontemperate figures, that more protein per hec-tare will be produced if the whole aerial bio-mass of the legume is harvested, thrown intoour energy vat, the leaf protein extracted forhuman consumption, the carbohydrates forethanol production, the residues for return tothe soil.

We have spoken only of the oil yields of theoil palm, There is still a lot of unused biomass,which could go, depending on the outcomesof our systems analysis, into ethanol produc-tion, internal or external combustion devicesand/or soil amendments.

Not all, but most palms, survive or thrive inthe humid tropics. Like the oil palm, they aremultiple-use plants, prime candidates for theupper or intermediate stories in the multitieredagroecosystem for the humid tropics. Could wenot multiply the yields of these unstudiedpalms by 10 as we have done with the Hevearubber plant. Let’s look briefly at one men-tioned by Amazonian expert R. E. Shultes (23):

Orbignya martiana: One palm may producea ton of nuts a year, 198 pounds of which iskernel . . . with up to 72 percent of an almost

SEEDS

colorless oil very similar in composition tococonut oil. The seed cake remaining, con-taining 27 percent protein, is an excellent ani-mal feed. I read this as a ton of biomass peryear, more than 100 pounds of which is oil.I don’t know that these figures are more orless reliable than those with which Calvinderived 50 barrels of diesel per acre. Conser-vatively, it would take four of these produc-tive palms to produce one barrel of oil peryear, or 200 trees to produce 50 barrels, Frommy experience in Latin America, I would pinmy 50 barrels/acre hope on the palm beforeI would Calvin’s Diesel Tree. Calvin figuredat least 100 trees per acre, but his trees were1 m in diameter. I don’t know any palms thatbig. Thin canopied palms would permit inter-cropping of food crops, which I speculatewould be impossible in the shade of “dieseltrees.”

Note that with our hypothetical Orbignya,with no genetic research, we are getting 50 bar-rels of palm oil per acre, with a residue of 1,900pounds per tree. We have assumed a tree pro-ducing 2,000 pounds of fruit, 100 pounds ofwhich is oil (3,300 pounds are reported, withan oil yield in excess of 200 pounds oil per tree).Assume 300 to 350 pounds per barrel of oil. Wecan further assume after the extraction of our100 pounds of oil, we have 1,900 pounds ofbiomass in the pot, 900 pounds of which might,conservatively, be water. Of the remaining1,000 pounds, perhaps there is another 100pounds of protein, per tree, and 900 poundsof carbohydrates, etc., 400 pounds of whichmight give us another barrel of ethanol per hec-tare. So, hypothetically we have 100 pounds ofprotein and 2 barrels of ethanol as byproductfrom our 1 barrel

The technologyscenario:

1. oil extraction2. carbohydrate

tion; and

of palm oil.

needed for this oil palm

(available for oil palm);fermentation and distilla-

3. protein purification and sanitation, forhuman or animal production.

There are palms for the arid tropics, for thehumid tropics, for brackish swamps, for fresh-

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water swamp situations, and for our sewagesump, all potentially intercroppable with otherfood/energy/chemurgic crops. But the GeneRevolutionist has not started to tailor these spe-cies to specific environments and to increasetheir yields. And we have not even talked aboutthe waxes, steroids, leaf-proteins, and ethanolthat could be produced by the leaves. Somepalms will disappear before we have studiedtheir potential.

Production of conventional palm oil (fromElaeis) was expected to total 4.3 million MTin 1979-80, compared to 3.9 million MT in1978-79 [1). Whether or not these are viewed

handled in the U.S. market. Residues could beused for alcohol or methane generation, or asa soil amendment.

Some prices quoted in the Chemical Market-ing Reporter for various tropical oilseeds dur-ing 1979 are avocado ($ S. IS/lb), castor oil($0.40/lb), coconut ($0.57/lb), corn ($0.50/lb),cottonseed ($0.18/lb), oiticica ($0.60/lb), palm($0.33/ lb), palm kernel ($0.42 /lb), and soybean($0.48/lb). The newly generated market for jo-joba “oil” has a cult of followers, but this so-called oil is a liquid wax, unique to the jojobaamong plants. Soy oil, peanut oil, and sun-flower oil have been used as diesel substitutes.

as petroleum alternatives, many oilseeds are

ALLELOPATHY

Allelopathy has not yet been developed to bean alternative to herbicides. But if differentchemurgic species are selectively herbicidal,as one gathers from reading the allelopathicliterature, then all these herbicidal activitiesshould be cataloged. Residues of the allelo-pathic species might then be returned to theintercropped agroecosystem where its her-bicidal effects will do the most good and leastharm. One can even suggest how coumarin-containing residues (Melilotus, Trigonella, etc.)can be used to stimulate rooting in the soft-wood cuttings used for propagation in our trop-ical agroecosystem (17). Steenhagen and Zim-dahl (26) show that the hydrocarbon-producing

Euphorbia esula reduces the frequency ofquackgrass and ragweed, but also reduces thegrowth of tomato seedlings. Dry leaves of themedicinal species, Parthenium hysterophorus,inhibit growth and modulation in legumes,branching in tomato and plant height in ragi(Eleusine coracana) and reduce the yield ofbean, tomato, and ragi. On the other hand, theleaves stimulate the growth of Pennisetumamericanum (15). Such data are being gener-ated rapidly, but there seems to be no com-puterized catalog to enable us to evaluate anduse these data effectively in planning multiuseagroecosystems.

DRUG CROPS

The Economic Botany Laboratory specializesin medicinal plants. We have found that thereare often huge residues of biomass followingdrug extraction. It takes 11/2 MT of dry stemand bark of Maytenus to yield a gram ofmaytansine, one of the anticancer superstarsof the last decade.

Bruceine, cassia, caffeine, cocaine, helio-tropic, ipecac, papain, pilocarpine, quinine,quinidine, reserpine, rutin, steroids, and the-ophylline: these are a few drugs that can be

harvested in the humid tropics. Many of theseare million dollar items that could be extractedon-site as income producers, leaving behind 99percent of the biomass for food and/or fuel pro-duction. Some drugs might be byproducts fromconventional foods, e.g., caffeine from coffeeand tea, theophylline from tea, steroids fromlegumes, rutin from buckwheats. The steroidsonce derived from tropical dioscoreas (“bar-basco”) are now largely derived as byproductsof legumes and agaves.

237

ESSENTIAL OIL

The United States imports nearly 10,000 MTof essential oils at close to $100 million peryear. This probably represents the distillationof about one million MT of biomass, 99 per-cent of which could have been funnelled intofood and fuel production as byproducts. By nomeans all of these essential oils are humid trop-ical species, but I list a few that are from thehumid tropics:

● Trees: bay, bergamot, camphor, cassia,cinnamon, clove, copaiba, grapefruit,guaiac, lemon, lime, linaloe, nutmeg, petit-grain, ylang-ylang

● Forbs: cardamon, citronella, ginger, lem-ongrass, palmarosa, patchouli, vetiver.

The trees might be considered as alternatingtrees or strata with other trees, like palms, inthe upper strata of our multitiered agroecosys-tem. The forbs might be considered for theground layer. Our Gene Revolutionists shouldalready be looking for tolerance to shade androot competition in our lower tier, and toler-ance to root competition in candidates for theupper tier.

FIBER CROPS

On the last day of October 1980, an official steriods, waxes, leaf protein and alcohol, evencalled from the Strategic Materials Department tequila, could be produced. Many natural fibersto ask where in our 50 States we could grow can be produced in the humid tropics, amongseveral strategic materials. Among them were them abaca, baobob, coir, cotton, ensete, hemp,two tropical fibers, abaca and sisal, the former henequen, jute, kenaf, remaie, roselle, sisal,adapted more to the humid tropics, the latter snakeplant, sunn hemp, etc. As the cost of pe-more to the arid tropics. With sisal, fiber yields trochemicals rise, some economists predict aare only 3 percent of the leaves. From the re- return to natural fibers instead of synthetics.maining 97 percent biomass, I am certain that

Some chemicals in this group approach theclassical petrochemical or “neoclassical”botanochemicals. Swedish and Finnish firmsare reported to have developed an efficientturpentine car engine that runs on turpentineproduced from the oleoresin of scotch pine.High road mileage is claimed for turpentine(20). Presumably, yields of tropical pines maybe higher than the temperate pines. The GeneRevolutionist would be charged with increas-ing both the nut (pinyon) and turpentine forspecified intercropping stratagems under spec-ified ecological conditions.

Copaiba oil, traded at over $2.00 per kilo,may or may not be the same as the oil fromMelvin Calvin’s tropical “diesel tree” Copaifera

langsdorfii. According to Dr. Calvin, (4) 11/2inch holes drilled halfway through large treesabout 2 feet above the ground yield about 20liters of “diesel” (mostly 2 or 3 main C-15 ses-quiterpenes and 30 or 40 minor C-15 sesquiter-penes) in two hours. The holes are bunged andretapped again in about 6 months, and said toyield another 20 liters of diesel, or 40 liters ofdiesel per year per tree. This is exactly the sameyield reported in Grieve’s Modern Herbal,1931. Dr. Calvin, perhaps optimistically, cal-culates that we can get 25 barrels of diesel peracre per year on a sustainable basis from thecopaiba tree (18). Unfortunately, the tree seemsto be intolerant of frost. I will be getting resinfrom an equally productive timber species ofCopaifera during my next trip to Panama.

238

Gum arabic, guar, karaya, locust, myrrh, ported with a value of $608,346. More than 23olibanum, and tragacanth are among some of million pounds of guar gum were imported inthe vegetable gums now traded. With problems that same month. Acacia, Tamarinds, andin Iran, a major producer of tragacanth, prices Sterculia are major tropical sources of gumsof tragacanth have risen considerably. In April that can provide renewable harvests in inter-1979, 56,900 pounds of tragacanth- were im- cropping- strategies.

RUBBER

The first Hevea plantation set out in the FarEast yielded about 450 pounds dry rubber peracre, while currently available clones yieldabout 3,000 lbs/acre (<10 barrels). New chem-ical treatments applicable during tapping canincrease the figure to 6,000 lbs an improvementof 13.3 times. These yields are available whileleaving the biomass intact. Other options mightbe to grow whole plants for rubber extractionbetween our upper story palms in the humidtropics. The Petroleum Plant from whichCalvin once projected 50 barrels per acre couldbe grown in the humid tropics as well as thearid tropics. Detractors from Calvin say yieldswould be closer to two barrels than 50 barrelsfrom the “Petroleum Plant.”

Calvin’s plant has received other headlinesunder the name of gopherweed (Euphorbialathyris):

Melvin Calvin, Nobel Laureate in Chem-istry, believes that the U.S. could producemore than 2 million barrels a day of gopheroil

by 1995, The Department of Energy hasgranted Calvin $250,000 to continue his re-search. Marvin Bagby, head of the AgricultureDepartments hydrocarbon-plant researchproject, thinks that gopherweed is the leaderamong 45 hydrocarbon-bearing plants thathave commercial promise (l).

Other species of Euphorbiaceae are betteradapted to and more productive in TMF thanthe headliners Calvin promoted. The latex ofmilkweeds could more appropriately be fun-nelled into rubber production. Be it spurge ormilkweed as hydrocarbon sources, the wholeplant would be thrown into the extraction vat,with waxes, drugs, rubber, leaf-protein andethanol as feasible byproducts, all grown be-tween our upper-story palm trees. WhetherCalvin gets 2, 10, 25, or 50 barrels/acre of pe-troleum or rubber from the “petroleum plant,”gopherweed,” or “diesel plants,” I maintainthat the ethanol potential from the residues hasmore energy content than what he obtains.

WAX CROPS

Waxes tend to be more frequently derivedfrom arid land plants than humid tropical spe-cies. But if the wax can be taken as byproduct,like ethanol, following extraction of edible leafprotein, humid tropical waxes might becomeexport money-makers. In the Chemical Mar-keting Report, one finds such waxes as thetemperate bayberry wax ($3.00/kg), the aridlands candelilla wax ($3.()()/kg), and the sub-tropical carnauba wax ($4.00/kg). Yields rarelyexceed 1 percent of the plant, leaving 99 per-cent of the biomass as waste, or better as leaf-

protein or energy stock. One second-growth“weed,” Calathea lutea, of the humid tropics,could serve as source for food, wax, and bio-mass, as could members of the banana family.The Calathea is easily propagated with as manyas 30,000 plants per hectare, yielding up to 70pounds of wax per acre (23). I project thatwould leave at least 29,700 pounds dry weightof biomass in the vat for leaf protein andethanol production. This leaves the under-ground roots untapped. Aerial biomass yieldsof 18 MT/ha might complement the edible-

239

rooted Calthea allouia (12 MT root/ha). Here other tropical plants, now all but unexploited,we must remember that increases in the below- can yield food, fiber, fuel, and residue for theground yields will usually be compensated for energy farm of the humid tropics.by losses in above-ground yields. Calathea and

Neither the Weed Science Society of Amer-ica (WSSA) nor the oil companies have loudlyadvocated the use of biomass as an energyalternative in the past. I find it interesting thatthere were five items in the October 1980Newsletter of the WSSA hinting at plants asa source of energy. Not necessarily believingthe figures myself, I summarize the estimatesfrom that WSSA newsletter:

●

●

●

●

●

It

Euphorbia: 50-125 bbls/ha,Salsola: Arizona grant to make fuel fromthe Russian thistle, a serious weed.Asclepias: Improved variety of milkweedcould be source of biomass for syntheticfuels and chemical feedstocks and a sourceof fat, protein, oil and fiber. Lab estimateof 60 bbls/ha crude oil.Parthenium: Guayule provides a latex thatcan be used for fuel, petrochemicals, andrubbers.Simmondsia: Speculation holds thatmature jojobas might produce the equiv-alent of 50 bbls/ha.

might be added that these optimistic esti-mates are based on marginal weed species inareas of marginal inputs. But these are grossenergy outputs. Whether it would take 100 to250 bbls/ha input to obtain the 50 to 125 bbls/haoutput is speculative. No one has analyzed theenergy inputs required to obtain these opti-

TROPICAL MOIST

Do energy farms produce more biomass thanthe pristine moist forest produces? Those whospeak of highly productive TMF mention greatquantities of biomass. The climax forest is inequilibrium, metabolizing as much as it syn-thesizes, so that although gross production may

mistic outputs. Research should provide thesenumbers.

A more pessimistic note comes from Shell’s“Ecolibrium” 9(4):1980:

According to the Gold Kist plant officials,a good peanut crop can reap 142 gallons anacre. And, unlike alcohol from grain, youdon’t have to distill peanuts to get oil, you justsqueeze them. The peanut oil costs about$3.00 a gallon.

The 142 gallons an acre is equivalent to lessthan 10 barrels per hectare.

This shows the wide disparity in figures usedby optimists and pessimists. Scientific researchshould rectify this disparity.

It seems doubtful that the herbicide indus-try would encourage hand harvesting of weedsand their conversion into alcohol and/or pro-tein. I advocate just that in TMF countries withunemployed hungry people. Almost all studiesshow that hand weeding, though using humanlabor, results in better yields than herbicidecontrols. In some cultivated communities,weeds constitute 8 to 27 percent of the shootbiomass. This 25 percent might represent 2.5MT on a tropical hectare, which could beharvested and converted to fuel, at the sametime increasing the yield of the crops the weedswere competing with.

FOREST BIOMASS

be extremely high, metabolism erases theprofit, leaving no net biomass increase. Doagroecosystems produce more total biomassthan native forest ecosystems? I cannot saycategorically. The optimist figures on arid landweeds yielding 50 to 125 barrels of oil per hec-

240

tare; the pessimist peanut prospectus lies at lessthan 10 barrels per hectare. And we see esti-mates of up to 150 MT dry weight from sometropical grasses under sewage irrigation. Thesefigures suggest to net that agroforestry is moreproductive of biomass than the climax forest.Estimates of the net primary production oftropical forests (table 1) presented by UNESCO(27) range from 9 to 32.

For comparison, I list in tables 2 through 4some examples of yields of tropical crops thatcan be grown in the lands occupied by theforests mentioned in table 1. These data,gathered from a variety of sources, do not con-sistently represent maximums, minimums, ormeans, nor are such data available. Hence,these numbers cannot be compared.

Today the biomass data bank at the Eco-nomic Botany Laboratory has close to a thou-sand entries in it. EBL is probably the bestequipped lab in the USDA to compare biomasspotential of different monocultural, polycultural,and natural ecosystems. Consequently, I havebrought my computer to this workshop so youcan check it out on the spot. Incidentally, EBLis probably the best equipped lab in the USDAto give you the ecological amplitudes, nutri-tional analyses, and folk-medicinal attributesof the little known economic plants of TMF,some of which now extant, may soon beextinct.

Table 2.—Tropical Root Crops (yields in MT/ha)

Arrowroot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37Canna. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85Cassava . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56GalIan , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120Ginger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Groundnut (bambarra) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Leren . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Lotus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Peanut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Sweet Potato . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Taro . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128Turmeric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Yambean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90Yautia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Table 3.—Tropical Vegetables (yields in MT/ha)

Banana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 MCantaloupe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 MEggplant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .......24 MGarlic. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .......10 MOkra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23MOnion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29MPepper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14MPigeonpea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13MPlantain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45MPumpkin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23MSquash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23MTomato . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22MTomatillo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36MYardlona bean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 M

TTTTTTTTTTTTTT

Watermelon . . . . . . . . . . . . . . . . . . . . . . . .. ... ... ...20MT

Table 1 .—Estimates of Net Primary Production (MT/ha/yr) in Tropical Forests(UNESCO,1978)

Forest type Location Net production

Equatorial Yangambi, Zaire 32Equatorial Khao Chong, Thailand 29Secondary forest 40 years old Kade, Chana 24Lowland dipterocarp Pasoh, Malaysia 22Bamboo in monsoon forest Burma 20a

Subequatorial (Banco plateau) Ivory Coast 17Bamboo in rain forest Burma 16a

Dry deciduous Varanasi India 16Lower montane El Verde, Puerto Rico 16Subequatorial (Yapo plateau) Ivory Coast 15Seasonal rain Anguededou, coastal 13

Ivory CoastMangrove Puerto Rico 9aEstlrnate does not include roots.

241

Table 4.—Tropical Spices Table 5 presents estimates of standing phyto-

Trees:mass and net primary productivity for some

Allspice . . . . . . .Bayrum tree . . .Camphor . . . . . .Cassia . . . . . . . .Cinnamon . . . . .Mace . . . . . . . . .

Pimenta dioica of the various vegetation types that might bePimenta racemosa expected in a tropical country. I believe, butCinnamomum camphoraCinnamonmum aromaticumCinnamomum verumMyristica fragrans

cannot prove, that intensively- managed agro-ecosystems used in places formerly occupiedby these forest types could produce two to five

Herbs and vines: times as much (except for the alluvial swampLemon grass: Cymbopogon citratus 95 MT WM forests). I do not advocate replacement of for-Patchouli . . . . . . Pogostemon cablin 36 MT WMPepper, black . . Piper nigrum 6 MT (fr) est with agroecosystem, but better managementVanilla . . . . . . . . Vanilla fragrans 1 MT (sol) of existing agroecosystems.Vetiver . . . . . . . . Vetiveria zizaniodes 2.5 MT (rt)

Table 5.—Net Primary Productivity

Republic of Panama Republic of PanamaPhytomass NPP Phytomass NPP

MT/ha MT/ha MT/ha MT/ha

Tropical:Humid tropics:

Bright Ferrallitic Evergreen . . . . .Swamp Forest . . . . . . . . . . . . . . . .Bogs . . . . . . . . . . . . . . . . . . . . . . . .Monsoon Forest (Savanna) Red .Monsoon (Dark Soil) . . . . . . . . . . .Alluvial Forests . . . . . . . . . . . . . . .Mangrove . . . . . . . . . . . . . . . . . . . .Submontane Evergreen . . . . . . . .Submontane Monsoon . . . . . . . . .

240440

650500300200

80250130700450

1829

2725

150161570103529

Semiarid tropics: 107 14

Xerophytic Forest (Ferrallitic) . . .Grass Shrub Savanna

(Redbrown) . . . . . . . . . . . . . . . . .Grass Shrub Savanna (Black) . . .Grass Shrub Savanna

(Solonets) . . . . . . . . . . . . . . . . . .Swamp Savanna . . . . . . . . . . . . . .Alluvial Gallery . . . . . . . . . . . . . . .Sub montane Xerophytic

Forest . . . . . . . . . . . . . . . . . . . . .Sub montane Savanna . . . . . . . . .

250

4030

2060

200

20040

17

1211

71460

1512

Arid tropics: 7 2

Savanna (red-brown soils) . . . . . . 15 4Alluvial Gallery . . . . . . . . . . . . . . . 150 40Tropical Desert . . . . . . . . . . . . . . . 1.5 1Psammonphyte on sand . . . . . . . 1.0 0.1Desert (Coalessed soil) . . . . . . . . 1.0 0.2Halophytes (solanchaks) . . . . . . . 1.0 0.1Submontane Desert . . . . . . . . . . . 7.0 2.0

SOURCE Rodln and Brazi l in Lieth. 1978

Subtropical: 133 14

Humid subtropical: 366 25Bright ferrallitic Evergreen . . . . . 450 20Rendaina Evergreen . . . . . . . . . . . 380 16Prairie . . . . . . . . . . . . . . . . . . . . . . . 30 13Swamp Forest . . . . . . . . . . . . . . . . 400 22Meadow Bog . . . . . . . . . . . . . . . . . 200 130Gallery Forest . . . . . . . . . . . . . . . . 250 40Submontane Forest . . . . . . . . . . . 410 18

Semiarid subtropics: 99 14

Xerophytic Forests . . . . . . . . . . . . 170 16Shrub-steppe (Gray-Brown soil) . 35 10Shrub-steppe (Soloneta) . . . . . . . . 20 6Shrub-steppe (Chernoaenoid) . . . 25 8Psammophyte on sand. . . . . . . . . 20 5Halophytes on Glanchak . . . . . . . 1.5 0.5Gallery Forest . . . . . . . . . . . . . . . . 250 40Submontane Forest . . . . . . . . . . . 120 13Submontane Shrub-steppe . . . . . 99 14

Arid Subtropics: 14 7

Steppe desert (Serozem) . . . . . . . 12Desert (sub-desert soil) . . . . . . . . 2Psammonphytes on sand . . . . . . 3Desert on takyrs . . . . . . . . . . . . . . 1Halophyte on solonchak . . . . . . . 1Gallery Forest . . . . . . . . . . . . . . . . 200Submontane Desert (Serozem) . . 15Submontane Desert (Desert

soil) . . . . . . . . . . . . . . . . . . . . . . . 3

1010.10.50.2

9012

1

.

242

1.

2.

3,

4.5.

6.

7.

8.

9,

10.

11.

12.

13.14.

References Consulted(but not necessarily cited)

Anonymous, “Prices for the Oil Will AlwaysFollow the Lead of the Soybean Oil Market,”ChemicaZ Marketing Reporter, Nov. 12, 1979,Becking, J. H., “Nitrogen Fixation, Rubus Ellip-ticus,” J. E. Smith, Plant and Soil 53(4):541-545,1979,Broughton, W. J., “Effect of Various Covers onthe Performance of Elaeis Guineensis (Jacq.) onDifferent Soils,” Internat. Develop. Oil Palm,Inc., Soc. Planters, Kuala Lumpur, 1977.Calvin, Melvin, personal comunnication, 1979,Clark, W., “China’s Green Manure Revolution,”Science 80, September/October 69-73, 1980.Dudal, R., “Inventory of the Major Soils of theWorld With Special Reference to Mineral StressHazards,” AID, 1976.Duke, J. A., “The Quest for Tolerant Germ-plasm,” Crop Tolerance To Suboptimal LandConditions, ASA Spec. Publ. 32, ASA, Madison,Wis., 1978.Ewel, John, “Tropical Successions: ManifoldRoutes to Maturity,” Biotropica 12(2): supple-ment. Tropical successions, 1980.Felker, Peter, “Mesquite: An All Purpose Legu-minous Arid Land Tree, ” in AAAS SelectedSymposium 38, New Agricultural Crops(Boulder, CO: Westview Press, 1979).Fey, C. D., “General Principles Involved inScreening Plants for Aluminum and Manga-nese Tolerance, ” 1976.Haines, S. G., Haines, L, W., and White, G., “Le-guminous Plants Increase Sycamore Growth inNorthern Alabama,” SSSA Journ. 42(l): 130-132.Hart, R. D., “A Natural Ecosystem Analog Ap-proach to the Design of a Successional CropSystem for Tropical Forest Environments,” inTropical Succession, Biotropica 12(2): Supple-ment: 73-82, 1980.Holmes, LeRoy, personal communication, 1980.Janos, D, P., “Mycorrhizae Influence Tropical

15

16.

Succession,” in Tropical Succession, Biotropica12(2): Supplement: 56-64, 1980,Kanchan, S, D., and Jayachandra, “AllelopathicEfforts of Parthenium Hysterophorus L,, ”Plants and Soi] 53(1-2): 27-35, 1979.Leith, H. F. H. (cd.), “Patterns of Primary Pro-duction in the Biosphere,” Benchmark Papersin EcoZogy 18 (Stroudburg, PA: Dowden, Hut-chinson, & Ross, Inc., 1978).

17. Lipecki, L., and J. Selwa, “The Effect ofCoumarin and Some Related Compounds onthe Rooting of Softwood Cuttings of PrunusMahaleb,” Symp. Growth Regulators, Acta Hor-ticulture No. 80., 1979, 478 pp.

18. Maugh, T. H., “Unlike Money, Diesel FuelGrows on Trees,” Science 206:436, 1979.

19. Meyers, Norman, “The Sinking Ark, ” Perga-mon Press (Biddies Ltd. Guilford, Surrey, UK),1979, 307 pp.

20. Noble, B. F., “Car Fuel From Pine Trees?”CANOPY, April 1979, p. 14,

21, Plemmons, B., and J, W, Avault, “Six Tons ofCatfish Per Acre with Constant Aeration,” Loui-siana Agriculture, 1980.

22. Plucknett, D, L., “Summation,” AID, 1976,23

2425

26

27

Schultes, R. E., “The Amazonia as a Source ofNew Economic Plants,” Econ. Bet, 33(3): 259-266, 1980.Solar Times, October 1980,Spain, J. M., “Field Studies on Tolerance ofPlant Species and Cultivars to Acid Soil Con-ditions in Colombia,” 1976,Steenhagen, D, A., and Zimdahl, R. L., “Allelo-pathy of Leafi Spurge (Euphorbia esula),” WeedScience 27(l): 1-3, 1979.UNESCO, “Tropical Forest Ecosystems, ”UNESCO/UNEP/FAO, 1 9 7 8 , 6 8 3 p p . ”

28. Van Dyne, G, M,, Smith, F. M., Czaplewski, R.L., and Woodmansee, R. G., “Analyses and Syn-theses of Grassland Ecosystem Dynamics, ”Preprint 180, Ft. Collins, CO, 1976.

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243

APPENDIX A-MAGIC MOUNTAIN: 2000 ADby James A. Duke1

Twas the year 2000 on Magic Mountain, in theTropical Moist Forest Life Zone. None of the na-tives lived by the river anymore. After the last floodthey abandoned the last alluvial homesite andmoved up on top of Old Magic. This freed 100 oftheir most productive hectares for agriculture. Un-tended slopes yield 30 MT/ha biomass each yearand the ridges where they now have their resi-dences yield only 15. The bottomland they aban-doned, fertilized by the floods that used to destroytheir homes periodically, yields 150 MT/ha. Withthe help of leaf-protein extraction equipment, theyare getting 3 MT protein per bottomland hectare,but the bulk of their bottomland biomass goes intobarrels, as ethanol. Lo and behold, they are getting2 barrels of alcohol for every MT of biomass, usingfirewood and residues to fuel the distillation, ap-plying the ashes back to the farm. That’s big moneythese days with ethanol at $100 a barrel, oil at $200.Instead of sending them arms, powdered milk, pea-nut butter, and fertilizer, the United States sentthem LP (leaf protein) extractors, seeds (computer-selected for this ecosystem), inoculum, stills, andenergy-producing portajohns.

Back in the 1990s some of the donors from theoverdeveloped countries realized that they couldnitrogenate more acres in the tropical backwoodswith a kilo of inoculated legume seed than a kiloof nitrogen. Adventist Missionaries made theirpoint back in 1990 when they showed the nativesthat they could get 10 to 20 times as much proteinfrom leaves if they did the conversion themselvesrather than let the cattle do it. So now, each hec-tare gives 3 tons of protein instead of 300 kg. Asa byproduct they have 100 barrels of ethanol, worth$10,000. With their tropical climate, conducive tohigher productivity, they are now exporting ethanolto the United States at $100 a barrel, while theArabs are having trouble finding buyers for theiroil at $200 a barrel, Instead of bananas at 5¢ a fin-ger or coffee at one clam per kilo, the barge thatchugs up the river hauls ethanol out for those prof-ligate spenders up in the United States who are stillsitting on their coal, to give them the energetic up-per hand in case the Russians don’t get out of Po-land, Afghanistan, Syria, and Iran (all of whose oilhad been burned up by saboteurs).

1This is a fictional presentation created by Jim Duke for theOffice of Technology Assessment. It reflects the personal opin-ions of the author.

Neophytes to the Tropics thought that MagicMountain was Virgin Rain Forest, but those of usin the know knew that nearly all of Magic Moun-tain was a multitiered, multiuse agroecosystem.The Virgin Rain Forest was the next ridge over, byRocky Rapid River, i.e., Meyers Mountain. RockyRapid River still provides cold clear water and theelectricity consumed on Magic Mountain. MeyersMountain, now a State Park, has several endemicspecies that are being studied by the Natural Prod-ucts people looking for better contraceptives andcancer cures, Neophytes thought this was VirginForest because it had more than 100 tree speciesper hectare in at least two tiers. Palms and legumesstuck out on top, with coffee and cacao in the lowertiers of some, leguminous vines in others, lemon-grass in others, yams in others, and zingiberacousspices in the shade of others.

Finding forest on magic mountain surprised a lotof armchair botanists, who, back in the 1980s pre-dicted that the forest would be reduced to savan-noid “red desert, ” But there were at least threestrikes against the “red desert” hypothesis: 1) theSecretary of State convinced the President thattrees alleviated rather than aggravated the pollutionproblem, so Americans were not running a “DownWith Trees” campaign, 2) natives had experiencedfewer bug and disease problems in their multitieredagroecosystems than in their brief monocultural ex-periments, and 3) Americans had encouraged a for-est “barrier” between the hoof-and-mouth diseaseof Colombia and the Hamburger Farms in CentralAmerica. The Neophytes thought that the Ameri-cans had taught the Indians this multitiered ap-proach, but, in fact, the Indians had taught theAmericans. Even in temperate America, the In-dians were intercropping when Columbus got here,with beans fixing a little nitrogen to supplementthat left by the decaying fish they placed with theirC-4 corn seed. The C-3 pumpkins we used for ourThanksgiving pie were used by the Indians as well.But they knew that the cucurbits smothered weedslong before young Dr. Duke discovered that cucur-bits not only smothered the weeds, but allelochemi-cally discouraged them.

The standard of living was almost as high onMagic Mountain as it was in New York City. A fewhippies and naturalists thought it was even better.It seems that in spite of marvelous inventions insolar energy and energy conservation (halving theconsumption of individual appliances), the Amer-

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icans were still energy guzzlers. They now had elec-tric nail clippers, electric combs, and electric tooth-picks, and they had to recharge their electric carsin offpeak hours with their palm oil and ethanol-fueled generators. These were located on offshorebarges for the receipt of the barrels of ethanol andpalm oil flowing in from the neotropics. The gringostill heats his home 6 months of the year to 72° Fand cools it 6 months of the year to 62° F, wearingshort sleeves in the wintertime around the houseand coat and tie during his air-conditioned sum-mer, Jim Duke said you could fuel America withsewage-irrigated biomass (if Americans went veg-etarian) and Melvin Calvin said Arizona planted tothe petroleum plant (Euphorbia lathyris) couldsatisfy the energy needs of the United States. Szegoand Kemp said you could do it with Btu bushes. ButAmerica went on and paved its bottomlands, itsmost productive farmland, which now sells at$200,000 per hectare. No one really knew who wasright, Should they have believed Vergara and Pi-mentel who said that all the biomass in the UnitedStates would support only 21/2 percent of their en-ergy needs (while in 1980 concluded that biomassalready supplied 2 percent of U.S. energy consump-tion and could supply up to 20 percent by 2000),or estimates of 10 percent (like Dugas came up with-in California), or those who said U.S. consumptionabout equals the net annual storage of solar energyin U.S. biomass, or Vietmeyer who accepts Calvin’ssuggestion that Arizona planted with petroleumplants could fuel all the United States?

There aren’t too many animals on Magic Moun-tain and these are there more for biocontrol thanfor meat. Sam Swindell has a bunch of pigs that arerotated from one alluvial farm to another when thenutgrass gets out of control. Seems that the nutgrasswas evolving just as fast as the herbicides. The lastgeneration of nutgrass herbicides reduced yields ofthe crop by 50 percent. One group of hippies downin Guyana had started making a beverage (ChufaCola) out of the nutgrass tubers, using the aerial bi-omass to generate the energy to run their operation.But nutgrass got so rare that Chufa Cola is barelycompetitive with Coca Cola anymore. Tommy Tuck-er intercrops turkeys with the legumes in his or-chards, largely to control weeds as suggested bySurguladze. Joe Groats has a few goats he stakesout whenever the tropical Rubus the gringos intro-duced for nitrogen fixation gets out of hand.

The Rice-Azolla farmers let the geese help theAzolla keep down the other weeds, while the grasscarp keeps down the Azolla and finishes off the zeo-lite-treated human refuse. They’re returning the res-idues from the essential oil still provided by AID

to the soil. But not just any residue anywhere.Seems that back in 1985, Duke quit talking andcomputerized all that data showing which plants(and their residues) had positive effects like alfalfaon crop yields and which had negative effects oncrops and weeds. Getting 3 MT of leaf protein fromalfalfa left a lot of spent residue around, even afterethanol generation. Some of the triacontinol per-sisted even in these second generation residues,enough to boost the yields of tomatoes by 10 per-cent, beans by 15 percent. With the computerizedsystems analysis of the allelochemic insecticidesand fungicidal, as well as insect-regulatory aspectsof spent residues, there was real planning as to dis-tribution of the allelopathic residues. The localswent all out on Vietmeyer’s winged bean when theyfound germplasm for seeds resistant to bruchids.In the past, bruchids had consumed half of theirstored grain. This minor discovery had the effectof doubling their yields of dry beans. Besides, theygot more nitrogen fixed than from the haricot bean,and edible roots instead of poisonous roots.

Following up on McKell’s suggestion back in1980, the Magic Mountaineers are using native spe-cies in their multitiered agroecosystems. Ipecac,here, like ginseng to the north, only grows in theshade. The natives are using byproducts from theiroverstory tonka bean (coumarin producer Dipteryxodorata) to stimulate rooting of new cuttings ofipecac (Cephaelis ipecacuanha) as they harvestroots of the older ipecac. Coumarin has been shownto stimulate cuttings. Both these species, like shade-loving Piper dariense (used for toothache and fishpoison), are adapted to the cooler, higher slopes ofthe Subtropical Montane Forests.

Gradually, tonka beans and oil-producing palmsand diesel trees are being introduced into the for-est canopy as other species are felled or die. MagicMountaineers still don’t believe Calvin’s estimatesthat they can get 125 barrels of “diesel” per hec-tare from their “diesel trees,” Copaifera spp., butthe resin is now selling for $10 a kilo and they canharvest renewably a few hundred dollars worth ayear as they are harvesting ipecac, chicle, rubber,ivory palm, quinine, and tonka beans from TMFspecies over on Meyer’s Mountain. The nature lov-ers still prefer to gather their items renewably fromMeyer’s Mountain National Forest, while the home-bodies are transplanting their species as money-making trees for the upper story of their agrofor-estry enterprises.

One of the Magic Mountaineers was raising croc-odiles for the export market in his water chestnutpatch. If harvested young, they did not thrasharound too much and mess up his water chestnuts.

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However, the crocodiles did cut his fish and prawnyield by 50 percent. He had trouble getting his hidesshipped directly to the United States Endangeredspecies authorities thought that cultivating croco-diles might endanger them in the wild. AnotherMagic Mountaineer had been exporting butterfliesto the United States until the endangered speciespeople shut off the port. When the farmer aban-doned his operation, two species went extinct, asfar as Magic Mountain was concerned. Perhapsthey still exist over on Meyer’s Mountain. Anotherfarmer was exporting amaranth seed to the U.S.health food market until the regulators stoppedhim, trying to avoid the importation of anotherweed, Boy Scouts back in the United States quietlyfilled this market by harvesting the amaranth seedsfrom weedy cornfields.

On the gravelly limestone ridge, where the 4 mannual rainfall quickly percolated through, someof Felker’s Prosopis was doing well, but the nativesstill preferred the tamarinds (Dialium, Tamarin-dus). They tend to vary their diets with other le-gumes, some mentioned by Felker; Cassia, Entero-lobium, Hymenaea, Inga, Parkia, Prosopis, TheProsopis yield of 12 MT/ha did not carry so muchweight here in the humid tropics as it did back onthe Chilean desert. One Chilean tree was reportedto yield at the rate of 12,700 kg fruit/ha, clearly agood yield for the desert. But none of the Arid Trop-ical species compete well in the Humid Tropics andvice versa,

A cord of mesquite will yield 30 million Btu com-pared to 25 million Btu from a ton of coal. Arizonapinon-juniper yields 18 million Btu. And MagicMountaineers, still cooking with wood, were im-pressed by Vietmeyer’s statement that a hectare ofLeucaena would yield 10 times as much wood asa well-managed pine plantation. The new fuel-effi-cient stoves the Swedes sent cut down on firewoodconsumption, leaving them with less ash to fertil-ize their vegetable plots.

Some of the natives of Magic Mountain are notfond of Leucaena, some of them even lamentingthat they had sown it for cover on the old landslide.Its seeds were coming up everywhere, but it onlyseems to be a real weed on the scarp. Nitrogen is,after water, the most frequent limiting factor in theTropics, so Leucaena is viewed by some as a goodN source. Our Magic Mountaineers were im-pressed with Halliday’s statement that biological ni-trogen fixation is “economically more sound andenvironmentally more acceptable than nitrogen fer-tilizer use in agriculture” and his statistics; mostlegumes fix 100 kg/ha, with Leucaena at 350 kg/ha,

and a potential of 800 kg/ha, Bill Liebhardt esti-mated Rhizobial Nitrogen fixation of pure strandsof Leucaena at 50 to 900 kg/ha. Still, certain gov-ernment agencies sent millions of dollars worth ofN to the Third World, when appropriately inocu-lated legumes, cheaper to distribute, would havedone the job renewably. Efficiency was the excuse,it takes less paperwork to spend $100 million at onefell swoop than to make 100 separate million dol-lar investments.

The Chinese on the steep slopes of the wet sideof the mountain are intercropping azolla, rice, fishand duck, in their intricately terraced rice paddies.They were getting 15 MT rice per hectare as Clarkhad reported in 1980. They were not getting 150MT dry weight of Azolla as suggested by Clark, butthey had devised a system for raking off the bulkof the Azolla every 10 days, after it doubled its bi-omass, and adding the biomass as a mulch to truckgardens on the ferralsols. And they sell a lot ofazolla-fed fish and ducks off their rice terraces.There is a persistent rumor that they are addingnight soil to their rice-azolla farms. But their ter-raced slopes are as productive as the alluvial bot-tomland,

Duke had always pushed the sunchoke (sunflowerX artichoke) as a biomass candidate for the tem-perate zone. The Chinese have squeezed it, like somany other temperate species, into the humid trop-ics. Sunchoke accomplished some of the things en-thusiasts for perennial corn were pushing back inthe 1980s. The roots are perennial and produce atleast 20 MT/ha edible root, leaving behind morethan enough to reseed itself and feed the last of thewild peccaries. The annual sunflower parent wouldhave to be replanted but not the artichoke, it keptcoming back like a song, more like a weed. Onefarmer who wishes to go into a different agrotech-nology had to borrow the biocontrol pigs to clearhis land of sunchokes. Chinese learned to add theraw artichoke to Chinese dishes to substitute forwater chestnut. It also turns out that the aerial bio-mass, cut three or four times a year, was good forleaf protein and ethanol synthesis, Still this sun-choke did not yield as highly as some of the otherscenarios. Some of the Magic Mountaineers ac-cused Johnny Sunchokeseed of introducing a weedto the Tropics, Take it home, yankee.

Down in the swamps, the natives were produc-ing closer to the lower than the upper predictionsof DOE back in 1980, 60 to 270 barrels of ethanolper hectare from cattails. They were getting higheryields from some of the native swamp species Acro-stichum, Dieffenbachia, Gynerium, Erythrina,

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Montrichardia, Panicum and Pennisetum, speciesthat DOE had not even considered.

Before Panama took over the canal, U.S. germ-plasm specialists provided many useful palms fortrial on Magic Mountain. Finally the Orbignya fromBrazil was bearing seed, but the smuggled seed hadtriggered an incident. Brazil broke relations withPanama and the United States for collecting germ-plasm without a permit. Back in the 1980s at a con-gressional OTA workshop, Duke had wonderedabout some of Schultes’ optimistic numbers for Or-bignya martiana: trees reported to yield more thana MT of fruit per year, 10 percent of which was ker-nel, 50 percent of which was oil for a yield of 40kg oil per tree or a barrel of oil for every 4 trees,accompanied by 40 kg protein per tree and perhaps350 kg carbohydrate per tree. Duke feared theseprojections were optimistic, like Melvin Calvin’sestimates of gopherweed oil. Still he recommendedthat OTA urge investigation of all palms becausemany are adapted to marginal tropical habitats.Some of the Magic Mountaineers did get yields al-most that high with trees at 100 to 200 trees per hec-tare. Above this, per-tree yields dropped off. Still,some of our Magic Mountaineers are getting 100barrels of palm oil per hectare on marginal soils.There was almost as much protein, and more car-bohydrates for ethanol production.

Magic Mountaineers had really been impressedwith Mumpton’s zeolites. Zeolites increased theirfish biomass by 10 percent with 5 percent clinop-tilolite, chicken feed efficiencies by 20 percent with

10 percent zeolite, beef profitability by 20 percent,calf growth by 20 percent with 5 percent zeolite,and swine growth by 25 to 30 percent with 5 per-cent clinoptilolite. They are using the clinoptiloliteto treat feces in their portajohns, lessening the odor.

Zeolites have made a big difference in farming,too. The nitrogen is held longer after the zeolite isapplied to the soil. Near Panama City, the zeoliteswere being imported from the interior to slow-down plant uptake of heavy metals in the sewagesludge energy farms and in the purification of low-Btu methane produced by anaerobic fermentationof beef excrement in the Hamburger Farm.

One oilpalm farmer with several dozen hectarespersisted in grazing beef and milk cows in the par-tial shade of his oil palms and coconuts. He heardthat he could increase his oil yields by 2 MT (about6 barrels) per hectare simply by interplanting withtropical kudzu and butterfly pea. He found that bylimited grazing, he could maintain his oil produc-tion. When asked what he was doing with his oiland cattle he said, “Those carnivorous Americansare still after our cheap hamburgers. Why at somejoints you can get a centigrammer (centigram ham-burger) for $2.00. Some people hint that it’s lacedwith palm protein, one of our byproducts here. Andthe Americans are running their soybean farmswith diesel tractors fueled with palmoil. That isconsiderably cheaper than soyoil.” “And whatabout your milk?””Oh, we dehydrate that and sendit to the Americans too. ”

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