Page 102 - Calculating Agriculture Cover 20191124 STUDENT - A

9-14 Land, Soils and Fertilizers CH 9]

SOILS

Soil is a material composed of minerals, living organisms, organic matter, gas, and water. Soil is
the thin layer of material covering the earth’s surface that is formed from the weathering of rocks and
the other elements found in it that interact slowly yet constantly. It provides the structural support for
plants and nutrients used in agriculture along with a reservoir of water.
There are four main soil types that include sandy soil, silt soil, clay soil and loamy soil. These
types are defined by their particle size and their composition condition. Refer to Soil Texture Triangle
in Figure 9.13.
The National Cooperative Soil Survey identifies and maps over 20,000 different kinds of soil in
the United States. Most soils are given a name, which are generally
derived from the locale where the soil was first mapped. Soils are named
and classified on the basis of physical and chemical properties in their
horizons (layers). “Soil Taxonomy” uses color, texture, structure, and
other properties of the top two meters of soil to key the soil into a
classification system to help people use soil information.
Soils and their horizons differ from one another, depending on how
and when they formed. Soil scientists use five soil factors to explain how
soils form and to help them predict where different soils may occur. The
five factors contributing to soil formation are:
Parent material: Soils form in materials that have moved in from
elsewhere. Materials may have moved many miles or only a few
feet. Windblown loses have been common in the Midwest.
Sediments along rivers have different textures, depending on
whether the stream moves quickly or slowly. Fast-moving water
leaves gravel, rocks, and sand. Slow-moving water and lakes leave fine textured material like
clay and silt when sediments in the water settle out.
Climate: Temperature and moisture amounts cause different patterns of weathering and
leaching. Wind redistributes sand and other particles, especially in arid regions.
Topography: Slope of land affect the moisture and temperature of soil. Steep slopes facing the
sun are warmer. Steep soils may be eroded and lose their topsoil as they form. Deeper, darker
colored soils are expected on the bottom land.
Biological factors: Plants, animals, microorganisms, and humans affect soil formation. Animals
and microorganisms mix soils, affect the chemical properties, and form burrows and pores. Plant
roots open channels in the soils.
Time: Soil formation processes over time continuously. Over time, soils exhibit features that
reflect the other forming factors. Recently deposited materials or erosion change the
composition and strata of soils.

These soil-forming factors continue to affect soils even on stable landscapes. Materials are
deposited on their surface and blown or washed away from the surface. Additions, removals, and
alterations are slow or rapid, depending on climate, landscape position, and biological activity.
What are 5 benefits of soil?
 Soil sustains life.
 Soil allows food to grow and ultimately, feed the world.
 Soil contains many nutrients needed by all plants to grow.
 Healthy soil aids in the cleanliness of the environment – decreasing erosion and air
pollution.
 The healthier the soil, the more nutrients ANY plant can utilize.

Overview of Land Use in the United States-The U.S. has 2.43 billion acres of land. The total U.S.
cropland area is about 253 million acres and the number one crop grown is corn.
Range and pasture lands are located in all 50 states of the US. Privately owned range and pasture
lands amount to about 528 million acres in the contiguous 48 states.
Forest Land- Forest lands comprise 749 million acres which about 33 percent of all land in the U.S.

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