Fred Magdoff Dept. Plant & Soil Science Soils the 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 CO 2.

What do plants need?

Light Warmth Carbon dioxide (CO 2 ) Oxygen (O 2 ) Water Nutrients Anchorage

What do plants need? 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 (O 2 ) to roots Help get rid of CO 2 Water Most nutrients Anchorage

What else do SOILS provide? Partitioning rainfall (runoff vs. infiltration)

What else do SOILS provide? Partitioning rainfall (runoff vs. infiltration) Storehouse for Carbon

carbon dioxide (CO 2 ) (0.04% in the atmosphere) root respiration and 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

What else do SOILS provide? Partitioning rainfall (runoff vs. infiltration) 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

What else do SOILS provide? Partitioning rainfall (runoff vs. infiltration) Storehouse for Carbon Cleansing pollutants (seepage fields, manures, sludges) Building material

What else do SOILS provide? Partitioning rainfall (runoff vs. infiltration) Storehouse for Carbon Cleansing pollutants (seepage fields, manures, sludges) Building material Something to build on (buildings, roads)

What are soils made of? Minerals Organic matter Pores (water & air)

What are soils made of? Minerals Organic matter Pores (water & air)

Minerals SAND 2mm to 0.02mm diameter small pieces of minerals that are found in rocks such as quartz, feldspars, and amphiboles (alumnosilicates) SILT 0.02 to 0.002mm diameter minerals similar to sand CLAY <.002mm in diameter and colloidal frequently formed in soils Many types of clays (with different properties) Most clays have plate-like structure contain negative charge (cation exchange capacity, CEC).

What are soils made of? Minerals Organic matter Pores (water & air)

Organic Matter Living Dead Very 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 springtails moles 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.

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.

What are soils made of? Minerals Organic matter Pores (water & air)

Figure 6.1. Distribution of solids and pores in soil. air water minerals organic matter solidspores Soil dries down Soil wets-up during rain

air water minerals organic matter solidspores Soil wets-up during rain

air water minerals organic matter solidspores Soil dries down

large pore intermediate pore 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 Nutrients released Aggregation increased Pore structure improved Humus and other growth promoting substances Reduced soil-borne diseases, parasitic nematodes Improved tilth and 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

What causes soils to be different from one another? 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.

What causes soils to be different from one another? Climate — Intensive weathering under hot and humid conditions. — Weathering and soil development are very slow under arid conditions.

What causes soils to be different from one another? vegetation — Grassland soils tend to have much higher levels of organic matter and are more fertile than soils developed under forest.

What causes soils to be different from one another? time — It takes time for forces of weather and influence of vegetation and slope position to be expressed.

What causes soils to be different from one another? 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.