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RECEIVE:
<br />additions, losses, transfers, and transformations of energy and matter or the ability to support
<br />rooted plants in a natural environment.
<br />The upper limit of soil is the boundary between soil and air, shallow water, live plants, or plant
<br />materials that have not begun to decompose. Areas are not considered to have soil if the surface
<br />is permanently covered by water too deep (typically more than 2.5 meters) for the growth of
<br />rooted plants.
<br />The lower boundary that separates soil from the nonsoil underneath is most difficult to define.
<br />Soil consists of horizons near the Earth's surface that, in contrast to the underlying parent
<br />material, have been altered by the interactions of climate, relief, and living organisms over time.
<br />Commonly, soil grades at its lower boundary to hard rock or to earthy materials virtually devoid
<br />of animals, roots, or other marks of biological activity. For purposes of classification, the lower
<br />boundary of soil is arbitrarily set at 200 cm.
<br />MRCS National Soils Survey Handbook
<br />657.5 rdentifiication of important farmlands.
<br />(2)
<br />(a) Prime farmlands.
<br />(1) General. Prime farmland is land that has the best combination of physical and chemical
<br />characteristics for producing food, feed, forage, lfber, and oilseed crops, and is also
<br />available for these uses (the land could be cropland, pastureland, rangeland, forest land,
<br />or other land, but not urban built -up land or water). It has the soil quality, growing
<br />season, and moisture supply needed to economically produce sustained high yields of
<br />crops when treated and managed, including water management, according to acceptable
<br />farming methods. In general, prime farmlands have an adequate and dependable water
<br />supply from precipitation or irrigation, a favorable temperature and growing season,
<br />acceptable acidity or alkalinity, acceptable salt and sodium content, and few or no rocks.
<br />They are permeable to water and air. Prime farmlands are not excessively erodible or
<br />saturated with water for a long period of time, and they either do not flood frequently or
<br />are protected from flooding. Examples of soils that qualify as prime farmland are Palouse
<br />silt loam, 0 to 7 percent slopes; Brookston silty clay loam, drained; and Tama silty clay
<br />loam, 0 to 5 percent slopes.
<br />Specific criteria Prime farmlands meet all the following criteria: Terms used in this
<br />section are defined in USDA publications: "Soil Taxonomy, Agriculture Handbook 436";
<br />"Soil Survey Manual, Agriculture Handbook 18 "; "Rainfall- erosion Losses From
<br />Cropland, Agriculture Handbook 282 "; "Wind Erosion Forces in the United States and
<br />Their Use in Predicting Soil Loss, Agriculture Handbook 346 "; and "Saline and Alkali
<br />Soils, Agriculture Handbook 60,"
<br />(i) The soils have:
<br />(a) Aquic, udic, ustic, or xeric moisture regimes and sufficient available water
<br />capacity within a depth of 40 inches (1 meter), or in the root zone (root zone is the
<br />part of the soil that is penetrated or can be penetrated by plant roots) if the root
<br />zone is less than 40 inches deep, to produce the commonly grown cultivated crops
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