SCORECARD IDENTIFIES COUNTIES WHERE ANIMAL WASTE PRODUCTION EXCEEDS THE NUTRIENT UPTAKE POTENTIAL OF CROPLAND
Scorecard utilizes a 1998 study by researchers from the Natural Resources Conservation Service of the U.S. Department of Agriculture to identify the counties in the US where the supply of nutrients from animal waste exceeds the nutrient requirements of non-legume crops and hay in that county. When nutrients from animal waste such as nitrogen and phosphorus exceed typical plant uptake and removal potential, these nutrients accumulate in the soil and increase the threat of pollution.
POLLUTION FROM NUTRIENT BUILDUP
Excess nitrogen and phosphorus can runoff from fields into waterways. When nitrogen and phosphorus reach streams and estuaries in high concentrations, they stimulate algal growth, which leads to low dissolved oxygen levels. Low dissolved oxygen can kill fish and other aquatic life. Furthermore, nitrogen from animal wastes is transformed to nitrates, which can leach from fields into waterways and contaminate drinking wells.
NATIONAL MAPS OF COUNTIES WITH EXCESS NUTRIENT PRODUCTION
Counties where nitrogen production in manure exceeds plant uptake
Counties where phosphorous production in manure exceeds plant uptake
LIMITATIONS OF USING NUTRIENT EXCESS TO IDENTIFY POLLUTION PROBLEMS
The NRCS study examines only one of several important factors influencing when nutrient loading can cause water pollution problems. It indicates when an area may be exporting excess nutrients because production exceeds possible crop uptake. However, other local environmental factors also influence whether predicted nutrient excesses will result in pollution problems. The vulnerability of receiving watersheds and factors that influence the environmental fate and transport of nitrogen or phosphorus (such as nutrient application rates and timing, soil type, climate, tillage and pasture management practices) have a significant impact on whether nutrient excess will lead to pollution of waterways.
Areas that do not have predicted excess nutrient production may also experience water pollution problems if wastes are poorly managed or local aquatic resources are vulnerable to nutrient loadings.
Note that nutrient estimates do not include estimates of nitrogen or phosphorus from sources other than animal waste, such as application of commercial fertilizers, atmospheric deposition, or mineralization of soil organic matter.