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Manure Nutrients Relative to the Capacity of Cropland and Pastureland to
Assimilate Nutrients:
Spatial and Temporal Trends for the United States
Executive Summary
Data from the Census of Agriculture were used to estimate livestock
populations, quantities of manure produced, and land available for manure
application for 1982, 1987, 1992, and 1997. Livestock include beef cattle, dairy
cattle, swine, and poultry. A descriptive analysis is presented of the temporal
and spatial changes in the number, size, and kind of livestock operations, and
the changes in animal units, quantity of manure nutrients produced, land
available for manure application, and excess manure nutrients at both the farm
level and the county level.
The analysis shows that the structure of animal agriculture has changed
dramatically over the last two decades. Small and medium-sized livestock
operations have been replaced by large operations at a steady rate. The total
number of livestock has remained relatively unchanged, but more livestock are
kept in confinement. The number of confined animals per operation has increased
for all major livestock types. A significant shift in the mix of livestock types
occurred as dairy cattle decreased in number and poultry and swine populations
increased. Livestock populations have become more spatially concentrated in
high-production areas. The number of animal units per acre of land available on
the farm for manure application for the largest operations is often high,
averaging more than eight confined animal units per acre for large poultry and
fattened cattle operations.
These changes in animal agriculture have resulted in increased problems
associated with the utilization and disposal of animal waste. As livestock
production has become more spatially concentrated, the amount of manure
nutrients relative to the assimilative capacity of land available on farms for
application has grown, especially in high production areas. Consequently,
off-farm export requirements are increasing. In some counties the production of
recoverable manure nutrients exceeds the assimilative capacity of all the
cropland and pastureland available for manure application in the county. The
number of these counties has significantly increased since 1982, indicating that
problems associated with animal waste utilization and disposal have become more
widespread over the last two decades as the structure of animal agriculture has
shifted toward fewer, but larger livestock operations.
The full text of this publication is available in Adobe Acrobat format.
Manure Nutrients Relative to the Capacity of Cropland and Pastureland to Assimilate
Nutrients (23 MB)
APPENDIX:
List of Maps and Data
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