Fred Magdoff Dept. Plant & Soil Science Soils the unappreciated natural resource

Fred MagdoffDept. Plant & Soil Science

Soilsthe unappreciated natural resource

You ask me to plow the ground. Shall I take a knife and tear my mother’s breast?

— Native American Chief

Many a hillside do the torrents furrow deeply, and down to the dark sea they rush headlong from the mountains, with a mightly roar, and the tilled fields of men are wasted.

— The Iliad

... for soil thou art and unto soil shalt thou

return.

— Book of Genesis

Then God Yahweh formed man out of the soil of the earth

— Book of Genesis

Adam — from Hebrew word for soil Eve — from the word for life

Soil + Life

Are you really “made” out of soil?

Where did the following come from:

•calcium in your bones

•phosphorus in bones and fats and nucleic acids

•nitrogen in proteins

•iron, potassium, magnesium, etc.

Are you really “made” out of soil?

And where did the carbon come from?

— From plants growing on and in soils and that fixed atmospheric CO2.

What do plants need?


Light Warmth Carbon dioxide (CO2) Oxygen (O2) Water Nutrients Anchorage


Nutrients C, H, O, N, P, K, Mg, Ca, S, Fe, Cu, Co, Ni, Mn, Mo, B, Zn, Cl

What do soils provide to plants?

Oxygen (O2) to roots Help get rid of CO2 Water Most nutrients Anchorage

What else do SOILS provide?

Partitioning rainfall (runoff vs. infiltration)



Storehouse for Carbon

carbon dioxide (CO2)(0.04% in the atmosphere)

root respirationand soil organic

matter decomposition

crop and animal residues

photosynthesis

respiration in stems

and leaves

crop harvest

Fig. 4.6 The role of soil organic matter in the carbon cycle.

carbon in soil

organic matter erosion



Storehouse for Carbon Cleansing pollutants (seepage

fields, manures, sludges)

Soils are a “living filter”

As water percolates through a soil

• pathogens may be deactivated

• Phosphorus is removed

• Nitrogen is removed

• Carbon is removed

• Many harmful chemicals removed




fields, manures, sludges) Building material




fields, manures, sludges) Building material Something to build on (buildings,

roads)

What are soils made of?

Minerals

Organic matter

Pores(water &

air)


Minerals

Organic matter

Pores(water &

air)

Minerals

SAND2mm to 0.02mm diametersmall pieces of minerals that are found in rocks such as quartz, feldspars, and amphiboles (alumnosilicates)

SILT0.02 to 0.002mm diameterminerals similar to sand

CLAY<.002mm in diameter and colloidalfrequently formed in soils Many types of clays (with different properties)Most clays have plate-like structure contain negative charge (cation exchange capacity, CEC).


Minerals

Organic matter

Pores(water &

air)

Organic Matter

LivingDeadVery Dead

Plants have evolved in a dynamic

relationship with other organisms

Living

• Beneficial and harmful

• Above and in the soil

—Living —nematodes

fungi

bacteria

mites

earthworms

springtailsmoles

plant roots

Figure 2.1 A nematode feeds on a fungus, part of a living system of checks and balances. Photo by Harold Jensen.

Figure 3.2 Root heavily infected with mycorrhizal fungi (note round spores at the end of some hyphae). Photo by Sara Wright.

spore

Figure 3.2 a. Sticky substance, glomalin, surrounding root heavily infected with mycorrhizal fungi. Photo by Sara Wright.

energy flows in direct ion of arrows

ground beet les 8 - 20 mm

1o = first level consumers

2o = second level consumers

3o = third level consumers

2o

2o- 3o

predatory mite .5 -1 mm

1o

2o

fly 1- 2 mm

rove beet les

rot ifera

1obacteria

fungiact inomycetes

lengths of organisms given in millimeters (25 mm = 1 in)

1 mm

1- 2 mm

scorpion1- 2 mm

70 -150 mmflatworms

ant5 -10 mm

10 mm

pseudo-

beet le mites

nematodes 1mm

nema-todes

.5 - 3 mmspringtails

sowbug10 mm

beet le

cent ipedes50 mm

earthworms50 -150 mm

mold mitebeet le mites1 mm

millipedes20 - 80 mm

.1- .5 mm

protozoa.01- .5 mm

2o

1o

1o

land slugs& snails 2 - 25 mm

2o

organic residues

feather-winged

white worms10 - 25 mm

Figure 3.1 Soil organisms and their roles in decomposing residues. Modified from D.L. Dindal, 1978.

— “Dead” —

Fresh residues in early stages of decomposition

— “Dead” —

Food supply for the vast number

of organisms that live in the

soil

Figure 2.2 Partially decomposed residues (the “dead”) removed from soil. Fragments of stems, roots, fungal hyphae, are all readily used by soil organisms.

— “VERY Dead” —

Well decomposed material, humus

Humus

• Colloidal

• Has many negative sites (can hold onto cations such as Ca++, Mg++, K+ = CEC)

Figure 4.5 Corn grown in nutrient solution with (right) and without (left) humic acids. Photo by R. Bartlett.

In this experiment by R. Bartlett and Yong Lee, adding humic acids to a nutrient solution increased the growth of both tomatoes and corn and increased the amount and branching of roots.


Minerals

Organic matter

Pores(water &

air)

Figure 6.1. Distribution of solids and pores in soil.

air

waterminerals

organic matter

solids pores

Soil dries down

Soil wets-up during

rain

air

waterminerals

organic matter

solids pores

Soil wets-up during

rain

air

water

minerals

organic matter

solids pores

Soil dries down

large pore

intermediatepore

small pore

Aggregate (crumb)

Figure 6.3 A well aggregated soil has a range of pore sizes. This medium size soil crumb is made up of many smaller ones. Very large pores occur between the medium size aggregates.

Add organic matter

Increased biological activity (& diversity)

Decomposition

Nutrientsreleased

Aggregation

increasedPore structure

improvedHumus and

othergrowth

promotingsubstances

Reducedsoil-borne diseases,parasitic nematodes

Improved tilthand water storage

HEALTHY PLANTS

Harmful substances detoxified

Figure 4.1 Adding organic matter results in many changes. Modified from Drinkwater & Oshins, 1999.

What causes soils to be different from one another?


parent material — The material from which

the soil derived. For example:

Lake bottom (much of Champlain Valley lowlands)

River flood plains (alluvial)Wind-blown material (loess)Rocks in place or moved by

glacier


position in the topography

— Soils on slopes are kept “young” because of erosion while those at the bottoms receive extra water and sediments from upslope.


Climate — Intensive weathering

under hot and humid conditions.

— Weathering and soil development are very slow under arid conditions.


vegetation — Grassland soils tend to

have much higher levels of organic matter and are more fertile than soils developed under forest.


time — It takes time for forces of

weather and influence of vegetation and slope position to be expressed.


human activity — Humans have a major

influence on many of the world’s soils. (Accelerated erosion, depletion of soil nutrients by intensive cropping, installation of tile drainage, etc.)

Tama soils were formed in silty material, called loess, under tall prairie grasses that have a deep fiberous root system and under relatively humid climate. Grasses have added organic matter, producing a relatively thick, dark surface layer. Erosion is a continuing problem with these soils.

The Paxton series consists of very deep, well drained soils on glacial till uplands. The dense subsurface till is characteristic of Paxton soils. Permeability is moderate in the surface layer and subsoil and slow or very slow in the substratum. Available water capacity is high. Very strongly acid to moderately acid. A seasonal high water table is at a depth of 1.5 to 2.5 feet.

Tifton soils occur throughout the Southern Coastal Plain in Georgia. Tifton soils formed in loamy sediments of marine origin. They are among the most important agricultural soils in the State. Cotton, peanuts, soybeans, and corn are the principal crops grown on these soils.

Drummer soils consists of very deep, poorly drained soils that formed in 40 to 60 in. of loess or other silty material and in the underlying stratified, loamy glacial drift. These soils formed under prairie vegetation. Drummer soils are the most extensive soils in Illinois. They are the most productive soils in the state. Corn and soybeans are the principal crops.

The Chesuncook soil series typifies the northern temperate and cool forested regions of Maine — moderately well drained on till plains, hills, ridges, and mountains. These soils have a high woodland productivity rating. The most common tree species are red spruce, balsam fir, yellow birch, American beech, sugar maple, white ash, and red maple.

Hilo soils have historically been used for sugarcane crops. With the decline of the sugar industry, there has been a shift toward truck crops, such as ginger and taro; orchard crops, such as macadamia and papaya; and forestry. These soils cover about 14,500 acres and are considered prime agricultural land. The Hilo series consists of very deep, moderately well drained soils that formed in many layers of volcanic ash with lesser amounts of dust from the deserts of central Asia.

Windsor soils are well suited to the highly diversified agriculture of Connecticut. They are the preferred soils for the production of shade tobacco. They are important for the production of fruit and vegetable crops, silage corn, and ornamental shrubs and trees. The Windsor series consists of very deep, excessively drained, rapidly permeable soils.

Bayamón soils are interspersed between limestone hills (haystacks) in northern Puerto Rico. They are used for sugarcane, pineapples (pictured above), a wide variety of food crops, pasture, and hay. Bayamón soils, formed in highly weathered, clayey marine sediments, they have low or medium fertility and are strongly acid to extremely acid throughout.

Houston Black soils are important agricultural soils. They are used extensively for grain sorghum, cotton, corn, small grains, and forage grasses. They also are important soils in many urban areas.) than any other state. These soils shrink when dry and swell when wet. Texas has about 15 million acres of Vertisols. Almost 2 million acres, or 13 percent, consists of Houston Black soils.

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Fred Magdoff Dept. Plant & Soil Science Soils the unappreciated natural resource