Nutrients in streams and ground water, as a measure of the degree to which nitrogen and phosphorous are being exported from agricultural lands. (Figs. 1, 2)

High levels of phosphorous in soils, because excess phosphorous can contribute to water pollution. (Fig. 3)

Counties that produce more phosphorous in animal manure than can be used locally. Phosphorous in manure, if not properly managed, may contribute to water pollution. Because manure is not generally transported long distances, counties with more phosphorous in manure than can be used on local crops must deal with an excess. (Fig. 4)

The amount by which nitrogen fertilizer applications exceed crop needs, because excess nutrients can contribute to water pollution. Also reported here is the number of counties in which nitrogen fertilizer applications exceed crop needs, as a measure of the prevalence of this phenomenon. (Fig. 5)

Concentrations of most forms of nitrogen and phosphorous considered to be water pollutants are generally higher in agricultural streams and ground water than streams and groundwater in residential or forest areas. About 5 percent of streams and 3 percent of ground water samples from agricultural areas exceeded U.S. Environmental Protection Agency (USEPA) drinking-water standards for nitrate (10 parts per million).

In 27 states, the majority of soils tested contained phosphorous at high or very high levels in 1996/1997, up from 24 states in 1989/1990. In 22 states, the proportion of soils testing high or very high increased, whereas in an equal number of states, this proportion decreased.

About 37 percent more nitrogen in fertilizer is applied, on a national basis, than is taken up by crops. This is slightly less than the percentage calculated for 1972, but the amount of excess has grown from 4 billion to 6 billion pounds. Excess nitrogen may contribute to air or water pollution or remain in the soil. In 87 percent of US counties, the application of nitrogen in fertilizer in 1992 exceeded the amount taken up by crops.

Since 1954, the number of counties in which more phosphorous from manure is produced than can be used in local crop production has more than doubled, and the location of such counties has moved south and west.

Nitrate in Agricultural Streams & Groundwater (2) Technical Note	Soils with High Phosphorous Levels, 1996/97 (3) Technical Note
Source: USDA, Natural Resources Conservation Service	Source: The Potash and Phosphate Institute

Counties Where Phosphorous from Manure Exceeds Crop Needs (4) Technical Note	Nitrogen Application and Crop Needs (5) Technical Note
Source: USDA, Natural Resources Conservation Service	Source: USDA, Natural Resources Conservation Service
This map identifies locations where possible phosphorous-related problems exist but does not indicate specific water pollution problems. Also, this map does not account for other sources of nutrients, such as fertilizer.	This graph shows the increase in the amount by which fertilizer application exceeds crop needs. The excess increased from roughly 4 billion pounds in 1972 to more than 6 billion pounds in 1997 ("residual," dotted line, left axis). The graph also shows the percentage by which application exceeds uptake, which was slightly less in 1997 than it was in 1972 ("input/output percentage," solid line, right axis). In 87 percent of US counties, the application of nitrogen in fertilizer in 1992 exceeded what was taken up by crops. Of these counties, about half exceeded plant needs by less than 50 percent, and about half by 50 percent or more.