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Review the indicators
at a glance
- How much of the “natural” area in farmlands is
in patches of different shapes? The size and shape of these
“natural” patches help determine the ecological services
they provide, including erosion control and wildlife habitat.
Data are not adequate for national reporting on this indicator.
Chemical and Physical Condition
Six indicators describe the chemical and physical condition of
farmlands, three that characterize farmland streams and groundwater
and three that tell us the state of the soil. (We complement these
measures with two biological indicators related to water and soil—see
Biological Components, below.)
To describe the condition of farmland streams and groundwater,
we include measures of pesticides, and of nitrate and phosphorus—two
important nutrients that, if present in excess, can cause problems.
An indicator measuring the quality of stream habitat complements
these measures (see Biological Components,
below).
To characterize the suitability of soils for growing crops, our
indicators track changes in soil organic matter, in the potential
of the soil to erode by wind and water, and in soil salinity. A
complementary indicator describes the microscopic animals in cropland
soils (see Biological Components, below).
- How much nitrate is there in farmland streams and groundwater?
High levels of nitrate in drinking water—especially untreated
well water—are a human health concern, and nitrate from the
nation’s rivers contributes to algal blooms in coastal waters.
About 20% of the groundwater wells and 10% of the stream sites
tested had nitrate concentrations that exceeded federal drinking
water standards. Monitored streams and groundwater in farmland
regions have higher concentrations of nitrate than those in urban
and suburban or forested areas.
- How much phosphorus is there in farmland streams? About
three-fourths of farmland stream sites had phosphorus concentrations
that exceeded the level recommended by the Environmental Protection
Agency to protect against excess algae growth. Concentrations
of phosphorus in monitored farmland streams were similar to those
in urban/suburban streams, and much higher concentrations than
streams in forested areas.
- How many pesticides are found in farmland streams and groundwater,
and how often do they exceed federal standards and guidelines?
Eighty-three percent of monitored streams in farmland areas had
at least one pesticide whose concentration exceeded aquatic life
guidelines; 4% had at least one compound that exceeded human health
standards or guidelines. All streams had at least one pesticide
at detectable levels throughout the year, and 75% had an average
of five or more. Fewer than 1% of groundwater sites in farmland
areas had pesticides in concentrations that exceeded human health
standards, and 40% of groundwater sites had no detectable pesticides.
- How much organic matter is there in cropland soils? Organic
matter improves the ability of soils to hold water, provides nutrients
for crops, reduces erosion, and can help to support soil microorganisms.
Data are not adequate for national reporting on this indicator.
- How much cropland is subject to erosion by wind or water?
From 1982 to 1997, the acreage of U.S. farmland with the greatest
potential for wind erosion decreased by nearly a third, to about
63 million acres, or about 15% of U.S. croplands. The area with
the greatest potential for water erosion also decreased by nearly
a third, to 89 million acres, or about 22% of U.S. croplands.
- How much cropland soil has high salt levels? High-salinity
soils, which typically result from irrigation in arid climates,
can reduce the ability of soils to support plant growth. Data
are not adequate for national reporting on this indicator.
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