Percent Change in Prime Farmland Used as Cropland, 1982 - 1992
This shaded polygon map shows the percent change in the amount of prime farmland used as cropland from 1982 to 1992 within each 8 digit hydrologic unit, using 1982 as a base year. The percentages are presented in four categories based on the following divisions: an increase of more than 5%, little change (less than 5% change), a decrease of 5% to 25%, and a decrease of over 25%. Areas with less than 5% prime farmland in both 1982 and 1992 are screened out. Areas with 95% or more Federal area are shown as gray.
Cautions for this Product:
Areas with small amounts of prime farmland may have very high rates of change. Changes may be due to either a change in the amount of prime farmland or the conversion of cropland on prime farmland to a non-cropland land cover/use. Data are not shown where prime farmland is less than 5% of the total area. Data are not collected on Federal land. Data are not available for Alaska or the Pacific Basin. Data for Puerto Rico and the U.S. Virgin Islands is shown by 6-digit hydrologic unit.
Source: National Resources Inventory, 1997
NRI sample data are generally reliable at the 95% confidence interval for state and certain broad substate area analyses. Generally, analyses that aggregate data points by smaller geographic areas and/or more specific criteria result in fewer data points for each aggregation and therefore less reliable estimates. NRI maps reflect national patterns rather than site- specific information.
Aggregate Layer: 8 Digit Hydrologic Unit Areas with Federal Land
Other Layers Displayed: States, Rivers
A Land cover/use category that includes areas used for the production of adapted crops for harvest. Two subcategories of cropland are recognized: cultivated and noncultivated. Cultivated cropland comprises land in row crops or close-grown crops and also other cultivated cropland, for example, hayland or pastureland that is in a rotation with row or close-grown crops. Noncultivated cropland includes permanent hayland and horticultural cropland. [NRI-97]
Includes land identified as being in row or close crops, summer fallow, aquaculture in crop rotation or other cropland not planted -- including cropland in short-term set-aside programs; or land in horticulture that is double cropped; or land in hay which had at least one of the three previous years in row or close grown crops; or land in pasture which had at least one of the three previous years in row or close grown crops.
Includes land in horticulture that is not double- cropped; or land in hay which had not been in row or close-grown crops for any of the previous three years.
Land that has the best combination of physical and chemical characteristics for producing food, feed, forage, fiber, and oilseed crops and is also available for these uses. It has the soil quality, growing season, and moisture supply needed to produce economically sustained high yields of crops when treated and managed according to acceptable farming methods, including water management. In general, prime farmlands have an adequate and dependable water supply from precipitation or irrigation, a favorable temperature and growing season, acceptable acidity or alkalinity, acceptable salt and sodium content, and few or no rocks. They are permeable to water and air. Prime farmlands 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.[SSM, USDA Handbook No. 18, October 1993]
Product ID: 5039
Production Date: 1/25/01
Product Type: Map
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