'Humus, 'Fertilizers, Lime and Fertilizer .Inspection

Dr. H. J. Wheeler, Boston, Mass.

HUMUS plants as do certain of the well recognized

Before entering upon a discussion of organic materials, such as tankage andfertilizers and their use, it is of first im~ cottonseed meal.portance to speak of humus; since, if the I recall experiments made several yearssoil is not adequately supplied with hu- ago, in which I grew the perennial flatmus, plants cannot make their best pea for two or three years on the samegrowth, neither can fertilizers exert their land and then turned the crop under andmaximum effect. sowed barley. The barley was much bet-

Wl1at is needed in Florida soils is not ter than it was on adjoining land whereorganic matter which has reached the flat peas had not been grown previously,most advanced stageof decomposition, but and the crop appeared to be abundantlyrather organic matter in thevarious stageJ supplied with nitrogen. The next .year,of decomposition. I have known soils ex- however, there was no appreciable in­ceedingly rich in organic matter, a large crease in the crop :where flat peas hadpart of which had decomposed to such an been turned under a year before as com..extent and was in such a state that it pared with the plot where no flat peascould be dissolved from the soil by treat- had been grown. This showed that thement with ammonia water; and yet these nitrogen contained in the flat peas hadsame soils were very unproductive be- practically all been utilized by the cropcause of the need of organic matter in the which followed or that it had been trans­~arlier stages of decomposition. In gen- formed into nitrates which had leachederal it. is probably safe to state that the away.richer the plants are in protein, the cl1ief For crops or plants which may be in­nitrogenous constituent, the more quickly jured by the presence of too much nitro­they decompose. On this account many gen, particularly toward the close of orof the non-legumes decompose rather just following the rainy season, it mightmore slowly and furnish organic matter be better in son1e cases to use non-Ie...~n the various stages of decomposition for gumes as cover crops, rather than le~

a longer time than the legumes do. gumes. It is generally recognized, thatYoung and tender legumes decay very certain crops or plants are more affectedrapidly. In fact, they act almost as quick., by various diseases if the plants are over­ly as sources of available ammonia for fertilized with ammonia at certain stages

103

104 FLORIDA STATE HORTICULTURAL SOCIETY

of their growth, than if they are suppliedwith properly balanced plant food whichdoes not carry an excess of ammonia.

Another point· in connection with le­gumes ought to be mentioned. Everyonerecognizes the importance of getting ni­trogen out of the air and of utilizinglegumes wllerever they can be utilized toadvantage. Until quite recently somemistaken notions have existed in regardto the amount of nitrogen 'which they fixfrom the air; since, as long as t4ere ispresent in the soil an abundant supply ofcombined- nitrogen in forms which theplants can utilize, they take it up insteadof assimilating atmospheric. nitrogen toany considerable extent. Recent experi­ments in the Middle West have shownwhere legumes and non-legumes havebeen grown side by side and then removedfrom the land, that the soil has been madepoorer in nitrogen where the legumeswere grown than where the land was de­vot~d to non-legumes. Even if the cropsare left on the farm and are returned inmanure, a large percentage of the ammo­nia is finally lost before the plant residuesin the form 'of liquid and solid manureare returned to the land. On this ac­count, if one wishes to add to the soil thegreatest amount of nitrogen from atmos­pheric sources, the legumes must begrown on land which is not already richin combined nitrogen, and they must thenbe plowed under~

When plant residues are applied to thesoil, the complex nitrogenous compoundswhich are contained in them are soonbroken up through the activity of bac­teria and the other naturally-existing mi­cro-organisms of the soil. While these

changes are taking place, some plants areable to assimilate directly certain of themore simple organic nitrogenous com­pounds, comparable to those producedfrom hair, wool, and other complex or­ganic nitrogenous compounds :when sub­jected to suitable factory preparation andtreatment .for fertilizer uses. The greaterportion of the nitrogen·, however, is trans­formed into ammonia by the agencies justmentioned, which in turrl is transforlnedin the soil into nitrous acid and finallyinto nitric acid. This l1itric acid then en­ters into combination with potash, soda,lime, or magnesia, from which it is takenup by plants unless lost in the drainagewaters. In Indiana even aluminum ni­trate has been known to be formed in soilsto suchan extent that it became poison­ous to vegetation. In other words, thiscompound may act in the same way ascertain of the other soluble aluminuml

salts.The various changes in plant residues:

take place more readily in soil well sup_·plied with moisture, and at fairly hightemperatures, than in rather dry soil, es­pecially when the temperature is low..The formation of nitrates is said to oc­cur most actively at a temperature ofabout 98° F.; hence, in many cases soilnear the surface in summer becomes too­hot fbr the most rapid formation of ni­trates.

It is not necessary from the standpointof the plant that all of the nitrogen, asid.efrom the small amount which is taken upin simple organic "forms, be changed intonitrates; for at least many kinds of plantsat certain stages of their growth are ableto use some nitrogen while stilll combined

FLORIDA STATE HORTICULTURAL SOCIETY 105

as ammonia. On the other hand, if thereis too great and sudden a formation ofammonia, owing to the conditions beingunfavorable to its transformation into ni­trates, there is a possibility that ammonia

. may in some cases accumulate in the soilto such an extent as to be injurious toplants. In a word, the most importantproblems in connection with the feedingof plants are the selection of the properplant foods and the compounding of thevarious materials in such proportions aswill insure a proper and adequate supplyof all necessary plant foods to meet theplant requirements from seeding time un­til full maturity is reached.

Even if fertilizers are supplied in ade­quate quantities and of the rigl1t analysis,it is al~o important to have the right pro­portions of the different materials used inthe minures. This may best be illus­trated by citing my own experiment withfertilizers in Aroostook County, Maine. Ifound it possible to produce 30-40 bush­els more of potatoes per acre with onefertilizer than with another, even whenan analysis of both would show the samepercentages of ammonia, available phos­phoric acid, and potash. The factors de~

termining the difference in yields in thesecases were the kinds of materials andtheir availabi,lity. Thus the difference inthe value of the product from an acre ofland produced by the two fertilizers hav­ing the same analysis was enough in mostseasons to pay the entire cost of the fer""tilizer used. It is because of these impor­tant considerations that a careful study ofsoil and climatic conditions and of soilap.d plant requirements is necessary in or-

der to manufacture fertilizers which willgive the best possible results.

FERTILIZERS

Ammonia.-I notice that the previousspeaker spoke of ammonia as that ingre­dient of the fertilizer which ."producesplant growth." I know it is a more orless common practice nowadays to speakof nitrogen, or ammonia, as that whicf!causes growth, of phosphoric acid as thatwhich produces the seed, and 'of' ,potashas the fertilizer ingredient which causesthe production of starch, sugar, and cellu­lose. We must not forget, however, thatthere are at least ten different plant foods,all of which are important to the properfunctioning of the plant; and if anyoneof these is entirely lacking, the plant willnot thrive. Therefore, iron, magnesia,.and lime are as necessary to growth asnitrogen is. We are led, however, tothink of nitrogen as especially necessaryto growth for the reason that when it isdeficient in a soil, plants generally takeon a light or yellow color and present anunthrifty appearance. And yet, I haveseen Indian corn which looked as light­colored and unthrifty as a plant possiblycould, when supplied with everything aplant requires excepting iron, b~t which,.as soon as iron was supplied, recovered itsnormal green appearance and throve per­fectly.

Another important consideration inconnection with the use of fertilizers istheir effect upon the soil. Nitrates, forexample, are subject to ready loss -byleaching on sandy soils if heavy rains oc­cur, and nitrate of soda in particular

106 FLORIDA STATE HORTICULTURAL SOCIETY

.tends to deflocculate clay soils and serious­ly injure their physical condition. Onacid soils nitrate of soda tends graduallyto correct the acid condition; and if thesoil is of such a physical character that itis not likely to be injured by the residualsodium carbonates, the after effect fromthe use of nitrate of soda is beneficial.

Sulphate of ammonia is not so subjectto leaching as nitrate of soda; yet if itwere used as the exclusive source of ni­trogen on a highly calcareous soil, there isa possibility that so much ammonia wouldbe liberated at once that some of it mightescape into the air and be lost, or even,under such conditions, cause direct injuryto plants, many of wh1ch are very sensi­tive to its presence in large quantities.,Sulphate of ammonia also tenqs to nlakesoils acid on account of the fact fhat theammonia is largely changed to nitric acidin the soil, which further adds for a timeto the marked acidity :created by the resid­ual sulphuric acid that was combined withthe anlmonia at the outset.

Calcium nitrate and potassium nitrateare both subject to ready loss by leachingin open sandy soils in case heavy rainsoccur. For crops which are greatly inneed of lime, especially when they aregrown on acid soils, calcium nitrate hasdistinct advantages; whereas for certainroot crops which can use some soda, incase the supply of potash becomes de­ficient, nitrate of soda may be a more~fficient or better source of nitrogen.

If calcium cy·anamid is introduced intofertilizers in snlall amounts under cer..tain chemical conditions, the nitrogenmay be largely transformed into urea, amost valuable organic source of nitrogen

for plants. On the other hand, if it isintroduced into fertilizers under otherconditions or in large quantities or if it isapplied directly to the soil under the usualconditions, large amounts of dicyanodi...amid are formed from it-a compoundwhich is highly toxic to plants. It is onthis account that calcium cyanamid of it~

self is usually considered unsuited for useas a top d:ressing or direct application togrowjng crops or trees. It is on this ac­count, also, that it must be applied two tothree weeks before ,the seed is sown in .or­der not to injure the young rootlets.

There is a possibility that in the nearfuture ammonium chloride may be placedon the market as a source of ammonia.If this occurs, it will have to be used witheven more care than sulphate of ammo..nia, especially on acid soils.

The important feature in connectionwith fertilizers is to have such quantitiesand such proportions of various materialsused as to exert the best and most favor­able influence upon plant growth, taking;into account, also, the effect of the ferti­lizers upon the physical and chemical con..dition of the soil. It is possible with aclear understanding of these points to useSUCll proportions, for example, 0 f certainnitrates, ammonium salts or other mate­rials, as. to avoid the ill effects which mayarise from their exclusive use as sourcesof ammonia; for when combined in theproper proportion's and in a proper man­ner, the various draw'backs mentionedmay be largely or wholly avoided, bymaking the effect of one substance coun­teract the unfavorable effect of another.

A further interesting phase of the ni­trogen problem is that of denitrification,

\

FLORIDA STATE ~HORTICULTURAL SOCIETY .107

or the destruction of nitrates within thesoil. It has been proved by the mostpainstaking experiments that if a soil be­comes water-logged up to a certain limit,nitrates instead of being formed or con­$erved -in the soil, begin to undergo de­composition, especially if the soil con­tains considerable amounts of freS'h ma­nures and certain other kinds of organicmatter in the early stages of decomposi­tion. This change may go only so farthat ammonia is formed; or it may evenprogress to such an extent that the majorpart of the nitrogen existing in nitratesalready in the soil or applied to it in fer­tilizers, may be changed into gaseousfonn and thrown off into the air. Thenitrogen would then be in the same formas the nitrogen in the air which we arebreathing in this room at the present mo­ment, and it would be of no more use toplants than the naturally-existing free ni­trogen already in the air. A very smallpart of the nitrogen under these condi­tions is transformed into organic materialconsisting of the micro-organisms whichbring about this change. Thus it is im­portant that soils be properly drained. Ifthey are not, organic material which hasconsiderably decomposed or which hasbeen well composted is far safer than or­ganic material in a less advanced stage ofdecomposition, since the latter is capableof supplying a greater amount of nutri­ment to the denitrifying organisms.

Phosphoric Acid.-In regard to phos­phoric acid, it is a well-known fact thatin Europe in the early days no such thing

)

'8 superphosphate, or acid phosphate, was. nown!' Due, however, to the work of

. : 'Von Liebig during the latter part of the

first half of the preceding century, it wasshown that the crop-producing efficiencyof ground bone was very greatly in­creased by treating it with sulphuric acid(oil of vitriol). Still later phosphaterock, which is a far less effective sourceof p'hosphoric acid than bone when bothare untreated, was also· subjected to thesame treatment, whereupon it was foundthat the available phosphoric acid, thusproduced, was as efficient a source ofplant food as if it had· 'been produced bytreatment of bone \vith sulphu'ric acid.

Ordinary bone and phosphate rock con­sist chiefly of tricalc-ium phosphate, some­times called a "three-lime" phosphate.In the manufacture of superphosphate(acid phosphate) either from phosphaterock or from bone, it is customary to addenough sulp,huric acid to combine withtwo of the three atoms of lime, so thatonly one atom of lime remains in com­bination with phosphoric acid. This re­maining compound containing only oneatom of lime is soluble in water, supply­ing what is known as usoluble phosphoricacid." The other two-thirds of.· the limein the bone or in the phosphate rock arechanged into land plaster, or gypsunl,which remains in the mixture. This,therefore, the farmer secures withoutcost, since the charge for the superphos­pha~e is based merely upon the percent­age of available phosphoric acid.

It has been found in some of the stateson the Pacific Coast and elsewhere thatsulphur, even in such combinations asland plaster, or gypsum, is very helpful tothe growth of certain plants; and it isnot at all impossible that the sulphur con­tained in the land plaster, associated with

108 FLORIDA STATE HORTICULTURAL SOCIETY

acid phosphate, or dissolved bone, is oftenof some' 'use to plants. It may 'not onlyserve as direct plant food, but, to a cer­tain extent, the gypsum may act as a lib-!eratot of potash; and if ammonia happensto be present in the soil in the form ofcarbonate, it may react with the ammoniaso as to change a part of it temporarilyinto sulphate, in which form it is non­volatile and cannot escape into the airand be lost.

Two great advantages are derivedfrom the use of superpHosphate, whethermade from bone or rock, namely: ( I )

it is soluble in water and hence can betaken up immediately by the plants, and(2) "it becomes better distributed in thesoil if applied in soluble form than if ap­plied in its untreated natural condition.To be sure, much of the soluble phos­phoric acid, upon application of a super­phosphate to the soil, is soon changed intoless soluble forms, known as "reverted"or "back-gone" phospllo·ric acid. Its ef.ficiency, after this reversion has takenplace, is determined to a considerable ex....tent by the character of the soil and therelative proportions of the various sub­stances with which the soluble phosphoricacid can combine. For example, if thesoil contains large quantities of aluminumand iron oxides, and little or no availablelime, there is a tendency for much of thephosphoric acid to enter into combinationwith the iron and aluminum and for butlittle of it to enter into combination withlime. It is on this account that it is ad­vantageous to make small or moderateapplications of lime from time to time tosoils where superphosphates are to be

used·,' provided crops are grown whichare not subject to injury by liming. Forcitrus, fruits, unfortunately, lime mustfor other reasons be used with exceedingcare and in very small quantities if at all

Much has been said and written in re­cent years about raw rock phosphate, or,in oth'er words, regarding phosphate rockwhich has not been subjected to treatmentwith sulphuric acid; and many extrava­gant claims have been made concerningits efficiency as plant food. It is of someagricultural value even without treatment,on certain soils, and its greatest efficiencyis observed when it is used on acid peator muck soils. The next best soils onwhich to use it would be upland soilswhich contain large amounts of acid or­ganic matter. However, for most cropsand soils throughout the greater portionof the United States and especially in theeast along the Atlantic seaboard, no otherform of phosphoric acid has proved equalto superphosphate prepared from bone orrock phosphate by treatment with sul­phuric acid. It has been found, for ex­ample, that if the raw rock phosphate isused on land' which has been recentlylimed or w:hich naturally contains a con­siderable amount of carbonate of lime, itsefficiency is very greatly reduced or insome cases practically nullified', for thereason that the acids of the soil or thosecontained in the rain water or producedas a result of nitrification and fermenta­tion are likely to attack the carbonate oflime before they can exert any materi~l

solvent action on the raw rock phosphate.It is for this reason that soft phosphate,which generally contains muoh carbonate

FLORIDA'STATE HORTICULTURAL SOCIETY 109

of lime, is often less efficient than. itwould be if it were entirely dissociatedfrom ca~bo~ate of lime.

When soluble phosphoric acid reactswith lime, it first forms dicalcium phos­phate or, in other words, a two-lime, orreverted, phosphate. This is still veryavailable to plants; for even though it isnot d-irectly soluble in water, it is readilydissolved by the action of plant roots andby water .containing carbonic acid, such,for example, as rain water and the nat­ural soil waters, which derive their car­bonic acid from the decomposition of theorganic matter of the soil.

I The chemist determines in' tIle labora­tory the amount of water-soluble phos­phoric acid and' also the amount of re­verted phosphoric acid and refers to thesum of the two as "avail.able" phosphoric

- acid.Another source of pllosphoric acid,

which was used in this country somewhatextensively before the war, 'is basic slagmeal, or Thomas phosphate. This wasproduced in the manufacture of steelfrom phospllate of iron by what is knownas the "basic" process. The phosphoricacid in this material is largely combinedwith lime ·in a different combination fromany of the other phosphates mentioned,­and some iron, manganese, and free limeare also present. As concerns the avail­ability of its phosphoric acid, it is some­what inferior to superphosphate. It is,however, superior in this respect to un­treated bone meal and is much superiorto raw rock phosphate or soft phosphate.Its availability to plants depends verylargely upon the conditions. under whichit is manufactured, and certain basic

slag meals produced in some Europeanworks before the war had a very lowavailability as compared with that pro­duced in others. Thus the source of thebasic slag meal, or Thon1as pllosphate,may be a very important considerationfrom the purchaser's standpoint.

Another new source of phosphoric acidis the so-called "ammo-phos," which is acombination of ammonia and phosphoricacid. This is a material which is as yetbut relatively little known in agriculturalcircles. It must be used experimentallyunder varying conditions and with a largenumber of different kinds of plants be­fore one ~an state definitely the condi­tions under which it can be used to thebest advantage, or can be sure of its realdesirability and of the efficiency of itsphosphoric acid as compared with phos­phoric acid in superp~osphate.

During and since the war many pro­cesses have been patented for ,the prepara­tion of phosphates for agricultural usefrom raw rock phosphate by differentmethods involving fusion with varioussubstances; but as yet none of these prod­ucts has apparently been able to hold itsown in competition with superphosphate,either by way of efficiency in crop pro­duction or economy of manufacture.

In connection with nly'o experiments,especially in the Middle West, I have beenastonished to find that as small amountsas 90-15° pounds of a relatively low­grade fertilizer, containing high percent­ages of phosphoric acid, have given in­creases of 8-15 bushels of wheat to theacre, 15-40 bushels of oats, and 10-25bushels of corn. In one case too poundsof fertilizer were used to the acre for

110 FLORIDA STATE HORTICULTURAL SOCIETY

sorghum. The sorghum was then manu­factured into syrup from both the ferti­lized and, unfertilized areas with the re­sult that where no fertilizer was used,the yield of syrup per acre was 67 gal­Ions; and where fertilizer was used, theyield was 140 gallons. This syrup wasworth at that time from 90 cents to $1.45per gallon; hence, the gross gain even at90 cents would be $65.70, from whiththere must be deducted only the verysmall cost of the 100 pounds of fertilizer:in order to show the net profit from thefertilization. '

Such increases often seem to be morethan might be expected from the mereplant-food effect .0£ the fertilizers; and itappears possible that in additiol1 to fur­nishing plant food in immediately avail­able form in close proximity to the youngrootlets of the plants, the fertilizers mayalso have a corrective effect by way ofovercoming the toxicity of certain sub­stances which may be present to an in­jurious extent in some of these soils.Furthermore, it is now known that fer­tilizers 11ave a very marked stimulatingeffect upon the development of certain ofthe soil bacteria upon which soil fertilityis very largely dependent. In connectionwith the first point raised, attentionshould be called to the fact that Conner,Abbott, and their associates in Indiana,found that in some soils alumintlm nitratewas present in suffiicient amounts to betoxic to plants. This is a substancewhich is decomposed by either lime orsU'perphosphates; and wherever such com­pounds are present in the soil, the appli­cation of fertilizer containing superphos­'phate would be expected to make the con-

ditions more congenial to the develop­ment of young plants. Similarly, at theRhode Island Agricultural ExperimentStation, Hartwell, Pember, Damon, andtheir associates, have found that wheresulphate of ammonia was appl·ied to thesoil for a series of years as the exclu­sive source of ammonia, aluminum sul­phate had been formed in the soil in suf­ficient amounts to render the soil unableto longer support the growth of variouskinds <;>f crops. It had prev·iously beenshown by the author of this paper tl1atthe existing toxicity, regardless of itscause, could be entirely' overcome by theus.e of lime. More recently it has beendemonstrated by Hartwell, Pember, Da­mon, and their associates, that exceeding­ly large applications of superphosphateare also capable of overcoming or greatlyreducing the toxicity of the aluminumsulphate; and this is due to the fact thatthe phosphoric acid upon combining ~ith

aluminum, changes it into a very insoltt­hie form which the plant cannot assimi­late. Ruprecht, while at the Massachu­setts Agricultural Experiment Station,found soluble, or toxic, aluminum saltspresent in certain soils. It appears, there­fore, that this is a condition which wehave but just begun to recognize in thiscountry. In fact, it is not improbablethat certain soluble salts of the protoxidof iron ma.y have similar effects, whichsuperphosphates are able to correct.

Where sufficient quantities of solublealuminum salts exist in the soil to preventutterly the growth of onions, beets, let­tuce, spinach, upland. cress, asparagus,cabbage, cauliflower, and, in fact, alarge number of other kinds of plants,

FLORIDA STATE HORTICULTURAL SOCIETY 111

there are still others which can thrive onsuch soils without difficulty. I 'refer par­ticularly to one of the flowering peren­nials, Silene orientalisJ which tllrove toperfection where most of the plants enu­merated above died before they had madematerially more growth than was possi­'hIe' from the stored-up food material inthe seed. The blackberry, for example,grew well on such soil. The Lima beanwas also able to make a fair growth,whereas the Golden Wax and other vari­eties of string beans were partial failures.Waternlelons ~grew splendidly, whereas'the cantaloupe practically failed. Otherplants were found to range between theseex:tremes.

Potash.-For most crops it is more orless immaterial what the source of tIlepotash is, as long as it is soluble in water,or is available to the roots of plants.However, citrus fruits, to'bacco, sugarbeets, and hops are illustrative of notedexceptions. The usual potash sourcesare muriate, wllich contains about twiceas much chlorine as potash; high-gradesulphate of potash, which contains littleor no chlorine; kainit, which contains twoor three times as much chlorine as pot­ash; and the double manure salt, contain­ing both sulphate of potash and sulphateof magnesia, and but relatively smallquantities of chlorine. It is the aim ofprogressive fertilizer manufacturers tosupply those forms of potash for specialcrops which are adapted to the kind ofplant to be fertilized. l

LIME

There are soils in Florida which con­tain a great abundance of carbonate oflime, in fact, far more than is desirable.On the other hand, there are some soilswhich are so acid and deficient in limethat its application is one of the first es­sentials to' success. For citrus trees, asstq.ted before, lime shoul,d be used withextreme caution, if at all, for we are wellaware of its various· il.l effects on citrustrees of all kinds. But if any lime is usedfor citrus trees, one should probably em­ploy only a small part of what is indi­cated as necessary to completely neutral­ize the soil; whereas, if one were growingcantaloupes, lettuce, spinach, beets, andmany other truck and field crops whichare greatly benefited by lime, liming ap­proximately to the full limit of the quan­titatively deternlined requirement mayprove helpful.

I have been much interested in whatone of the speakers has said regardingdie-back; for in connection with an ex­periment which I have been conductingwith oranges here in Florida, die-backwas markedly incr,eased where magnesiat}lime was used three years before at therate of only one ton per acre. The dis­ease was even worse when practicallypure lime was substituted for magnesianlime. The die-back was also accompa­nied by wither-tip and frenching. Thetrees in the same experiment which re..ceived no lime were far less affected withdie-back. Die-back was als9 present in

112 FLORIDA STATE HORTICULTURAL SOCIETY

an adjoining grove in which all the treeswere subsequently treated with bluestone(copper sulpha.te). Since it was my de­sire to I ascertain to what extent differentlime and fertilizer treatments would af­fect die-back, no bluestone was used onthe three experimental areas. Neverthe­less, die-back has now very largely disap­peared. If bluestone had also been usedon the experimental trees, it might havebeen inferred that the disappearance ofdie~back was chiefly. or wholly due to thebluestone. In view of the circumstances,however, it is evident that climatic orother c·onditions were responsible for' agood part of the improvement observed.*

I do not mean by this that I would notadvise the use of bluestone as a' meansof combating die-back, for it seems, atpresent, to be the best-known remedy forthis disease. It must, however, be usedwith care and moderation or trees may beinjured by it. I say this, notwithstand~

;*As the discussion following this paper wasdrawing to a close, one of Florida's authoritieson citrus diseases, citrus culture, and especiallyon the use of bluestone, disputed the statementtha.t die~back had largely disappeared withouttreatment, saying ,that he had visited the grovementioned a.nd found that this was not the case.I thereupon stated that what I said was basedupon the report of a man also familiar with Flor­ida. and its citrus problems, rather than upon myown examination, although I had observed amarked general improvement in the grove. Soonafter the meeting at Miami arrangements weremade through Professor Newell to have the grovecarefully examined and reported on by Mr.Gomme, county agent and citrus expert of PolkCo~ty, who reported as follows:

Section I. No Lime.-Not as heavy growth asin Section 2 or 3. Slight indication of frenching.Hail has 4a,maged young fruits-also young andold wood, causing the wood to split considerably.Fruit irregular in quantity. No S-,shaped growthapparent. No indi,cations o,f die-back by gumpockets or multiple buds. This. section could notbe recorded as having die-back.

ing that in some cases unusually largeamounts have been used without injury.In the course of my travels for severalyears through the citrus sections of thisState, covering in all many thousandmiles and visits made at different timesof the year, I have not found anyone whohas been able to- tell me positively all of'the different causes of die-back nor howit can always and surely be avoided. Ap­parently, there may be several causes. Atany rate, everything whicl1 can be done tothrow light upon anyone or more ofthese causes will be of material help tothe citrus industry. It is for this pur­pose, among others, that the companywith which I am connected is conductingseveral experiments in this State withcitrus fruits on I different types of soil.We cannot expect that the citrus industryof Florida will ever attain its highest andfullest development u~til the mysteriesconnected with the die-back problem have

Section 2. Limea Area-Magnesian Lime.­Hail damaged fruit and branches as in Section 1.Small amount of frenching. Growth in general isbetter than that in -Section 1 or 3. S-shapedgrowth is present in almost all trees but thereare no indications of die-back by gum pockets ormultiple buds. This section shows vigorous andhealthy growth. .

Section 3. Limed Area-Non-Magnesian Lime.-Die-back present on a few trees which showgum pocke~s, multiple buds, frenching, and brownexudation on wood. This condition is not ex­tensive, although it is marked on a few trees.The fruit and wood had been considerably dam­aged by hail. As in 1 and 2, the damage seemsto be more marked on the younger wood.

The Grove Across the Road from the AboveThree Sections.-This grove has been treated withbluestone. No die-back is apparent though a fewS-shaped branches were notIced. There has evi­dently been die-back in this grove at some earlierperiod. as some of the old wood is stained, but no 'gum pockets or multiple buds were found on theyounger growth.

FLORIDA STATE HORTICULTURAL SO·CIETY 113

been more fully explained. Until weknow more of the causes and of themeans of avoiding this disease, we shallbe in. essentially the same position as thephysicians and veterinarians who were at­tempting to combat yellow fever and ma­laria in the human family, and the Texasfever in cattle, before the relationship ofthe mosquito and the tick to the transmis­sion of these diseases was definitely as­certained. Most thorough and carefulexperiments should be made on every dif­ferent type of soil used in this State forthe growth of citrus trees, and this seemsto be one of the greatest needs of the cit­rus industry in Florida at the presenttime. It is not enough to have one ex­periment station, but experiments shouldbe conducted in all of the important citrusdistricts in which different types of soilare represented.

FERTILIZER INSPECTION

Before closing, I wish to say a wordabout the fertilizer law in Florida. Itrust I may be able to qualify as a compe­tent witness for the reason that I was forfour years connected with the fertilizerinspection in Massachu~etts, and for morethan twenty years had general charge ofthe chemical work connected with ferti­lizer inspection in Rhode Island.

T.· notice that there is a tendency in some·states to. require the manu:facturer toname the sources of the materials used inhis goods. In this connection it shouldnot be forgotten that requirements of thiskind. are of no use whatsoever, unless thechemist can substantiate or disprove theclaim of the manufacturer. Further-

more, such requirements are often con....trary to the best interests of both the pur­chaser of the fertilizer and the manufac­turer.

For example, there 'are a considerablenumber of materials rich in nitrogenwhich, in their natural, untreated condi­tion, are generally known to have a rela­tively low crop-producing value, but whenproperly treated in the fertilizer factory,are capable of transformation into mate­rials as valuable as or in some cases evenmore valuable than the best organic am­moniates with which we are familiar;such as, dried blood, tankage, and cotton­seed meal. If the manut"acturer is obligedto state that these materials are used, itis likely to create a prejudice against .thefertilizer, whereas the fertilizer reallywill be of very superior quality if thesesame materials are subjected to properfactory treatment at the outset. Further­more, after treatment, the nitrogen maybe present in compounds entirely differentfrom those existing before the treatmentwas applied. Such requirements areabout on a par with- the requirement thata manufacturer of turpentine must statethat he used .long-Ieaved pine in his prod­uct. It is true that special crops seem tobe of bett~r quality when certain ammo­niates are used than when others are em'!"ployed, and any manufacturer with hisfuture at stake strives to furnish thatwhich will give the best results. It is ofgreat importance to know the availabilityof the ammoniates in the fertilizer; but itcan do no one any good to state what theywere once, what they.. are not now, andwhat they never will be again. A law ofthis character, which requires the mak-

114 FLORIDA STATE HORTICULTURAL SO·CIETY

ing of statements that would be mislead­ing to the purchaser, is in many respectsworse than no law at all.

If I were to state that I used hair orwool in a fertilizer, the purchaser, know­ing the low value of each in its raw oruntreated state, would think that the fer­tilizer was inefficient. However, I cantake the hair off your individual headsor the wool off the backs of your sheep(with your permission) and, by chemicaltreatment in. the fertilizer factory, trans­form it into material as valuable as, oreven more valuable than, the best organicammoniate known. After such treatmentit would certainly no longer be hair; but itwould consist of a very large number ofdifferent nitrogenous compounds, manyof which no chemist could practicallyhope to identi.fy in making a fertilizeranalysis, and much less determine quan­titatively. In fact, if, under such circum­stances, I were to state that hair wasused, I should be telling you that some­thing was there which was really notthere.

I mention these points merely as illus­trative of tendencies in connection withsome recent fertilizer laws to requirestatements which are useless, absurd,positively misleading, and contrary-to thebest interests of the user of fertilizer. Ifyou wish to know the source of potash ina fertilizer, a chlorine test in addition tothe test for potash will usually tell allthat is required. If you wish to know thereal crop-producing value of a fertilizer,a determination of the percentage ofavailable phosphoric acid and potash, andthe availability of the nitrogen as shown

by the most reliable chemical methodsknown, affords the best possible means ofprotection for the purchaser. In thosestates where this plan has now been invogue for several years, the results havebeen most acceptable to the farmers.

I wish also to say a word about thecollection of samples of fertilizers. It isto be presumed that the object of a fer­tilizer inspection is to set forth the actualfacts as to the quality and analysis of thefertilizer. This being the case, it is oftl1e utmost importance that samples be sodrawn that they will truly represent thefertilizers which are being inspected.

If you were to make up a fertilizercontaining bone, tankage, and variousother materials, including potash salts,nitrates, sulphate of ammonia, and simi­lar materials, you might find, no matterhow accurately the mixture had beenmade, that some of the lighter materialsin the mixture would tend to come to thetop of the bag when shaken up in transitor handled in the storehouse. Conse­quently, the only way that a truly repre­sentative sample can be secur~d is to haveit drawn with a sampling implementwhich extends the entire length of thebag. The sampler should not be openeduntil it has been fully- inserted. It shouldthen be opened throughout the entirelength, filled, closed, and then with­drawn. Such sampling-rods are in exist­ence and are used exclusively in many ofthe states. These secure a tru'e core offertilizer extending the entire length ofthe bag. A perfect mixture of such coreswill give a true test of the character ofthe goods, if properly handled and an­alyzed.

FL'ORIDA STATE HORTICULTURAL SOCIETY 115

It is also important that samples bedrawn from such a number of bags aswill properly represent any given lot offertilizer. If there is a small number, allshould be sampled; and if there are manybags, samples should be drawn from notless than 10-20% of those present. Greatcare must also be taken in properly mix­ing the samples after they are drawn, sothat a uniform, composite sample can be

, secured for analysis. If I were merelyto draw a sample of fertilizer with myhand ·from the tops of bags in a shipmentand were to send it to your state chemistfor analysis, the chances are that hewould report that the analysis did notagree with the guaranty. Imagine fora moment that each of you is a manufac­turer and I the purchaser. You will ap­preciate the position in which you wouldfind yourselves, if I used such an analysisas a basis for non-payment of the goodsand as a means of having the goods con­fiscated. It must be obvious that such asituation as this would add to your over­head costs in the manufacture of ferti­lizers and to the prices which you wouldhave to charge me for them; or the alter­native would be that you would be drivenfrom business in the State.

'My conception of a fertilizer inspectionis that it should be conducted in such away, and ~he law sho~ld be so drawn, thatit affords protection to the purchaser andat the same time protects the honest man..ufacturer from injustice, imposition andthe perpetration of fraud on· the part ofany dishonest purchaser; in other words,the inspector of -fertilizers should bebacked by a just law and should stand asan absolutely neutral party, seeing to it

10

that absolute justice is done to both pro­ducer and· consumer. No other plan is a~

good for either the purchaser or the man­ufacturer.

DISCUSSION

Question: Mr. Chairman, the speakerhas already remarked that too much limemay be injurious to citrus fruits. Now Iwish to ask if too much iron, too muchmagnesia or too much of other materialswoula be injurious, and at what point thelimit should be set?

Answer: In regard to iron there maybe a situation 'where, on account of largeamounts of moisture and organ.ic matter,an oxide of iron may be formedl which, incertain combinations, may possibly be in...jurious to plants. We know, for exam­ple, that in some of the peat and mucksoils of Holland and Englapd, protosul­phate of iron has been found in suchquantities as to be destructive to vegeta­tion. There are instances on recordwhere soils contained so much magnesiaas to be injurious or almost sterile; butthis is doubtless inconceivable in the caseof Florida soils, since most of them con­tain very little magnesia, so little, in fact,that I suspect sonle magnesia may be ben­eficial for some crops under certain cir­cumstances. It is true that excessiveamounts of certain plant foods may beinjurious; but I do not think we have rea~son to fear the use of too much, especiallyin view of the present h.igh prices, whichhave unfortunately placed too great acurb upon their purchase.

Plants' differ very widely in their sus­ceptibility to injury by excessive amountsof certain salts of iron, magnesia, and

11"6 FLORIDA STATE HORTICULTURAL SOCIETY

other substances, which may be presentin the soil. A concrete illustration is af­forded in connection with experimentswhich I made several years ago in RhodeIsland. It was found that soil which hadpossibly never received any fertilizertreatment was exceedingly acid and con­tained substances so toxic to lettuce, spin­ach, beets, onions, asparagus, and manyother crops, that they could not be grownsuccessfully, and the application of ahighly acidic fertilizer further accentu­ated the difficulty; yet other plants grewto perfection On this soil. I mention thismerely as an illustration of the fact thatwe cannot conclude necessarily from theeffect of a given substance or substancesupon one kind of plant what the effectwill be upon others.

Question' : What do you think of cot­tonseed meal .as a source of ammonia?~nswer: If you get meal which does

not contain an undue amount of cotton­seed hulls, it generally has a fairly highavailability, although it is not so quick inits action as the ammonia in dried blood,tankage, and dried fish.

Mr. Beech: What can you say regard­ing calcium cyanamid? I am aware thatit is considered to be destructive to plantnematodes. I also understand it carriesa considerable amount of lime and that itshould be applied some time in advanceof the date of seeding.

Answer: It is undoubtedly true thatthis material is destructive to nematodes;but in order to prove highly effective inthis respect, it would have to be used infar greater quantities than should be rec-,ommended in 9rdinary agricultural prac­tice, especially in view of its high content

of nitrogen and lime. The material doeshave the advantage of supplying somelime, providing the plants grown and thesoils used require it. It is also true thatdicyanodiamid is formed from it when itcomes in contact with moisture in thesoil; and this material exerts a poisonousaction upon plant roots until it, in tum,is decomposed by the micro-organismsand by chemical ch-anges taking placewithin the soil. In general it should, beapplied two or preferably three weeks be..tore the seed is plal1ted. It can be mixedwith fertilizer in small quantities undersuch conditions that practically all of thenitrogen is transformed into urea, whichis a most excellent source of ammonia forplants. Under other conditions of manu...facture, dicyanodiamid may be formed,so that here again the skill and experienceof the manufacturer come into play.

Calcium 'cyan~mid· has been found to behighly injurious to workmen who arebrought extensively into contact with itin its natural state, especially if they havebeen imbibing alcoholic liquors. And Imay add that I am not bringing this up asan argument in- favor of prohibition, evenin this dry city.\ Mr. Gray: Just a question in relation

to bluestone. There are thousands ofbarrels of it used annually in this State;and in connection with your experiment,you show that the recovery of' the treeswas not necessarily due to bluestone.Where there are thousands of dollars atstake in connection with die-back, whatwould you advise a grower to do if thedisease appears?

Dr. Wheeler: I should by all meansadvise its use, until a time when some...

•

FLORIDA STATE HORTICULTURAL SOCIETY 117

thing better is found as a remedy or untilwe know how to prevent the disease.However, I should also advise great carein its use and the application of relativelysmall quantities. I hope some day wemay know more about it and how it acts.Until we do,' we cannot use it most in·telligently.

Question: I wish to ask what 'resultswould be secured by' the application ofsulphate of iron to the leaves of treeswhich show lack of color, or frenching?

:Dr. Wheeler: I think it is impossibleat this time to predict surely what effectspraying with protosulphate of ironwould have. Pineapples have beensprayed with it successfully in an exten..siye way in the Sandwich Islands on soilswhich contained excessive amounts ofmanganese, and where the plants were notable to secure enough i~on under theusual cultural conditions. Upon sprayingthe leaves, the plants absorbed' the ironand developed a healthy color and normalcrops became possible.

In ~orto Rico, Gile found that limecaused chlorosis and a bleaching effect onpineapples, which was overcome by spray­ing with protosulphate of iron. This re­sult indicates that the addition of lime tothe soil rendered the iron so insolublethat the

l

plants were not a1;>le to take upenough of it. Recent successful experi­ments have been made in spraying con­ifers with protosulphate of iron.' Re­peated sprayings with a I % solutioncaused certain kinds of pine trees to de­velop normally and to develop good color,whereas the use of a 2% solution resultedin positive injury to the trees.

It should be determined at the outsetby a few careful experiments whatstrength may be used on citrus trees with­out injury. The next problem will thenbe to ascertain whether frenching can beovercome to any extent by such spraying.Doubtless the results will depend uponwhat causes the frenching; for, accordingto many observations by our best author­ities, it seems to be caused by several dif­ferent conditions. It would be of the ut­most interest and importance to havespraying experiments made with proto­sulphate of iron and possibly with ferricchloride wherever frenching has followedan application of lime, in order to ascer­tain if the condition can be corrected. InPorto Rico, Gile found that several suc­cessive sprayings were necessary in orderto accomplish the wished-for results withpineapples; and obviously the finer the'spray and the more generally it is distrib­uted over the leaves, the better the re~ults

should Qe.I should like to ask if anyone in this

audience has sprayed with protosulphateof iron and, if so, with what result. Iask for the reason that about four yearsago I suggested the' idea of spraying withit to some of the members of this Societywho were present at our meeting at Ar­cadia. I am not aware that any of themever followed up the suggestion.

In general it has been found that whenprotosulphate of iron is applied to thesoil, it is not so effective in overcomingchlorosis, or frenching, as it is when it issprayed on the leaves, and very largequantities may often be necessary to caUsematerial benefit if the application is made

118 FLORIDA STATE HORTICULTURAL SOCIETY

to the soil. This is probably for the rea­son that lime and other basic compound9in ~e soil may make the iron insolubleas soon as the two compounds arebrought into contact with each other.

Answer from the Audience: I havemade experiments in spraying with proto­sulphate of iron, where the trees werevery much frenched and bore small fruit,and the result from one to three sprayingswas excellent. In other cases it apparent­ly did little or no good, but I presume theco.nditions giving rise to the frenchingwere different in the two cases.

Another answer: A'bout four yearsago, one or two acquaintances of minehad groves which showed frenching, andthey suspected that this was due to a lackof iron; and after spraying them withprotosulphate of iron from three to sixtimes at rather frequent intervals, amarked improvement in the trees re",suIted.

Anotller answer: I have noticed caseSof frenching in the Indian River regionwhere it seemed probable that too muchfertilizer had· been used, an·d I am satis..fied that you must have a satisfactoryamount of humus in the soil in order. toget the best results from fertilizer.

Dr. Wheeler: I have had my attentioncalled to cases of frenching which mayhave been caused by too much water andalso by too deep cultivation and injury tothe feeding roots. This injury to theroots results especially in cases where a

deep cutting disc or cutaway harrow isused instead of the acme harrow whichworks the- soil only to a sligllt depth.

What has been said about the impor­tance of humus in the soil is deserving ofspecial attention, since it is fundamentalto the best results in growing practicallyall kinds of crops, including citrus trees.The humus m'ay al~o play an importantpart in connection with the assimilationof iron. It is well known that wheregreat accumulations. of vegetable mattercome in contact with sands containingiron, the iron is often so largely dissolvedout that the sands become greatlybleached. This shows that the humus hasa solvent action on the iron. It is much'better to maintain conditions in the soil,if possible, w~ich will prevent frenchingthan to take the chance of curing it afterit appears. \

Another point concerning :which Iwould utter a caution is in regard to mak­ing spraying experiments with protosul­phate of iron on a large scale at the out­set. My advice ~ould be to determine ina small wayan a few branches, or at leaston a few trees, what strength of proto­sulphate of iron will be tolerated withoutinjury to the foliage or trees. By pro­ceeding cautiously in this way, no greatdamage can be done; and after this pointis determined, you can then spray exten­sively with reasonable safety, providedyou find it helpful. .