A Watershed Scale Ranking Scheme for Evaluating Impacts of AFOs on Water Quality
Hubbard, Robert K.
Magette, W. L.
Sheridan, J. M.
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Nonpoint sources of nitrogen (N) and phosphorus (P) leaving the agricultural landscape can cause eutrophication of surface water with associated degradation of water quality. Land use managers need tools to assist in making informed land use decisions and prescribing management practices to minimize potential N and P losses to water resources. A ranking scheme including both management practices and hydrologic and landscape properties was devised by Magette for both farm and watershed scale use. The scheme includes factors and weights for 1) Nutrient Usage, 2) Condition of Receiving Waters, 3) Ratio of Land to Water, 4) Farmyard Conditions, 5) Nutrient Application Rates, 6) Nutrient Application Times, 7) Soil Test P, 8) Overland Flow Distance, and 9) Runoff Risk. This paper presents the concepts involved in applying multi-parameter assessments to the landscape and using the assessment results to provide additional land management information relative to animal feeding operations (AFOs). The assessments proposed are intended to be a first step toward providing an objective basis by which to make environmental decisions about land management, both at the field and watershed level. The paper also presents results of using the ranking system to compare two different watershed subareas having different intensities of AFOs and compares the ranking system results with observed water quality measurements.