County-based estimates of nitrogen and phosphorus content of animal manure in the United States for 1982, 1987, and 1992.

These estimates are intended for large-scale ground- and surface-water
analyses of nutrient sources or changes in these sources. These data on
nutrients in manure can be compared to fertilizer inputs of nutrients.

This data set contains county estimates of nitrogen and phosphorus content of
animal wastes produced annually for the years 1982, 1987, and 1992. The
estimates are based on animal populations for those years from the 1992 Census
of Agriculture (U.S. Bureau of the Census, 1995) and methods for estimating the
nutrient content of manure from the Soil Conservation Service (1992).

The data set includes several components..

1. Spatial component - generalized county boundaries in ARC/INFO format/1/,
including nine INFO lookup tables containing animal counts and nutrient
estimates keyed to the county polygons using county code. (The county lines
were not used in the nutrient computations and are provided for displaying the
data as a courtesy to the user.) The data is organized by 5-digit state/county
FIPS (Federal Information Processing Standards) code. Another INFO table lists
the county names that correspond to the FIPS codes.

2. Tabular component - Nine tab-delimited ASCII lookup tables of animal counts
and nutrient estimates organized by 5-digit state/county FIPS (Federal
Information Processing Standards) code. Another table lists the county names
that correspond to the FIPS codes.

The amount of nitrogen and phosphorus present in manure (in kilograms) has been
calculated for each county of the United States. The procedure is identical to
that of Smith and others (1997), which covered the year 1987. Nutrient
estimates for the years 1982 and 1987 were computed again for the data set
here, and the results were checked against the results computed previously by
Alexander (written commun., 1992) for those years to ensure that they were
identical.

Limitations:

The estimates are county level and are based on estimates of the nutrient
content of animal manure produced per 1,000 pounds of animal weight on a daily
basis.

One important limitation of the animal population numbers from the Census of
Agriculture is that for some counties and animal classes, no data are reported.
This limitation reportedly is the result of restrictions on including animal
population data for counties where animal production is dominated or limited to
one business or farm. These data therefore are considered trade secrets and may
not be included in the county-based data. This limitation on population data at
the county level results in discrepancies when county-based data are summed and
compared to national animal population totals. At the present we have no way of
estimating animal populations for those counties with missing data and further
have no way of determining which counties are missing data. Therefore, the
animal manure, nitrogen and phosphorus estimates for some counties are an
underestimate of the total nutrient form animal manure in those counties.