Official prime farmland map units can be found in Section II of the electronic
Field Office Technical Guide for the State you are interested in:
http://efotg.sc.egov.usda.gov/ | This
information is also found on the
Web Soil Survey site.
General Criteria
Prime farmland soils are those that have the
best combination of physical and chemical characteristics for
producing food, feed, forage, fiber, and oilseed crops, and are
also available for these uses (the soil's use could be cropland,
pastureland, forest land, or other land, but not urban built-up
or water). It has the soil quality, growing season, and moisture
supply needed to economically produce sustained high yields of
crops when treated and managed, including water management,
according to acceptable farming methods. In general, prime
farmland soils have adequate and dependable precipitation, a
favorable temperature and growing season, acceptable acidity or
alkalinity, and few or no surface stones. They are permeable to
water and air. Prime farmland soils are not excessively erodible
or saturated with water for a long period of time, and they
either do not flood frequently or are protected from flooding.
Specific Criteria
Prime farmland soils in Massachusetts meet all
the following criteria: (Terms used are defined in USDA
publications: "Soil Taxonomy, Agriculture Handbook 435,"
"Soil Survey Manual, Agriculture Handbook 18," "Predicting
Rainfall Erosion Losses, Agriculture Handbook 537," and
"Wind Erosion Forces in the United States and Their Use in
Predicting Soil Loss, Agriculture Handbook 346."
A. The soils have aquic or udic
moisture regimes and sufficient available water
capacity within a depth of 40 inches (1 meter),
or in the root zone (root zone is the part of the
soil that is penetrated or can be penetrated by
plant roots) if it is less than 40 inches deep,
to produce the commonly grown cultivated crops (cultivated
crops include, but are not limited to grain,
forage, oilseed, sugar beets, vegetables, orchard,
vineyard, and bush fruit crops) adapted to the
region in 7 or more years of 10 (has at less 3.5
inches of available water in MLRA's, 144A and 149B,
and more than 3 inches of available water in MLRA's,
144B and 143 and 145), and
B. The soils have a temperature regime
that is frigid or mesic. These are soils that, at
a depth of 20 inches (50 cm.), have a mean annual
temperature between 32 and 59F (0-24C). In
addition, the mean summer temperature at this
depth in soils with an O horizon is higher than
47oF (8C), in soils that have no O horizon, the
mean summer temperature is higher than 59F (15C);
and,
C. The soils have a pH between
4.5 and 8.4 in all horizons within a depth of 40
inches (1 meter) or in the root zone if it is
less than 40 inches deep; and,
D. The soils either have no
water table or have a water table that is
maintained at a sufficient depth during the
cropping season to allow cultivated crops common
to the area to be grown; and,
E. The soils are not flooded
frequently during the growing season (less often
than once in 2 years); and,
F. The product of K (erodibility
factor) x percent slope is less than 2.0; and,
G. The soils have a
permeability rate of at least 0.06 inch (0.15 cm)
per hour in the upper 20 inches (50 cm); and,
H. Less than 10 percent of the
surface layer (upper 6 inches) in these soils
consists of rock fragments 3 inches (7.6 cm) to
10 inches (25 cm) in size.
