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Percent Change in Prime Farmland Area, 1982 - 1997
Description
This shaded polygon map shows the percent change
in the amount of prime farmland area from 1982
to 1997 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
2%, little change (less than 2% change), a
decrease of 2% to 15%, and a decrease of over
15%. Areas with less than 5% prime farmland in
both 1982 and 1997 are hatched. Areas with 95%
or more Federal area are shown as gray.
Cautions for this Product:
Since prime farmland may occupy only a small
percentage of the total area of some of the
polygons, the map may leave a misleading
impression as to the significance of higher
rates of change in some areas where there is
little prime farmland. 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.
Sources
Source:
National Resources Inventory, 1997
Distributor:
USDA-NRCS-RIAD
Reliability:
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.
Layers
Aggregate Layer:
8 Digit Hydrologic Unit Areas with Federal Land
Other Layers Displayed:
States, Rivers
Definitions
Federal land:
A land ownership class designating land that is
owned by the Federal Government. It does not
include, for example, trust lands administered
by the Bureau of Indian Affairs nor Tennessee
Valley Authority (TVA) land. No data are
collected for any year that land is in this
ownership. [NRI-97]
Prime farmland:
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 Information
Product ID:
5037
Production Date:
1/25/01
Product Type:
Map
For additional information
contact the Resources Inventory and Assessment Division.
Please include the Product ID you are inquiring about.
nri@wdc.usda.gov
or 1400 Independence Avenue SW - P.O. Box 2890 -
Washington D.C. 20013. If you use our analysis products,
please be aware of our disclaimer.
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