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657.5 Identification of important farmlands.
<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, fiber, and oilseed crops, and is also
<br />available for these uses (the land could be cropland, pastureland, rangeland, forest land, or
<br />other land, but not urban built -up land or water). It has the soil quality, growing season, and
<br />moisture supply needed to economically produce sustained high yields of crops when
<br />treated and managed, including water management, according to acceptable farming
<br />methods. In general, prime farmlands have an adequate and dependable water supply from
<br />precipitation or irrigation, a favorable temperature and growing season, acceptable acidity or
<br />alkalinity, acceptable salt and sodium content, and few or no rocks. They are permeable to
<br />water and air. Prime farmlands are not excessively erodible or saturated with water for a
<br />long period of time, and they either do not flood frequently or are protected from flooding.
<br />Examples of soils that qualify as prime farmland are Palouse silt loam, 0 to 7 percent
<br />slopes; Brookston silty clay loam, drained; and Tama silty clay loam, 0 to 5 percent slopes.
<br />(2) 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" "Soil
<br />Survey Manual, Agriculture Handbook 18 "; 'Rainfall- erosion Losses From Cropland,
<br />Agriculture Handbook 282 "; "Wind Erosion Forces in the United States and Their Use in
<br />Predicting Soil Loss, Agriculture Handbook 346" and "Saline and Alkali Soils, Agriculture
<br />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
<br />is the part of the soil that is penetrated or can be penetrated by plant roots) if
<br />the root zone is less than 40 inches deep, to produce the commonly grown
<br />cultivated crops (cultivated crops include, but are not limited to, grain, forage,
<br />fiber, oilseed, sugar beets, sugarcane, vegetables, tobacco, orchard,
<br />vineyard, and bush fruit crops) adapted to the region in 7 or more years out
<br />of 10; or
<br />(b) Xeric or ustic moisture regimes in which the available water capacity is
<br />limited, but the area has a developed irrigation water supply that is
<br />dependable (a dependable water supply is one in which enough water is
<br />available for irrigation in 8 out of 10 years for the crops commonly grown)
<br />and of adequate quality; or,
<br />(c) Aridic or torric moisture regimes, and the area has a developed irrigation
<br />water supply that is dependable and of adequate quality; and,
<br />(ii) The soils have a temperature regime that is frigid, mesic, thermic, or
<br />hyperthermic (pergelic and cryic regimes are excluded). These are soils that, at a
<br />depth of 20 inches (50 cm), have a mean annual temperature higher than 32 deg. F
<br />(0 deg. C). In addition, the mean summer temperature at this depth in soils with an O
<br />Revised September 2010 (PRO6) Attachment 2.04.9 -4 -1
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