THE CONCEPT AND NEED FOR A PHOSPHORUS ASSESSMENT-TOOL

Nonpoint sources of P leaving the agricultural landscape can cause eut rophication of surface water and the associated growth of undesirable aquatic plants. USDA is developing an indexing procedure for identifyi ng soils, landforms, and management practices that could have unfavora ble impacts on water bodies because of P movement. This indexing proce dure uses the characteristic of the field site, including soil erosion rates, runoff, available P soil test levels, and fertilizer and organ ic P application rates and methods to assess the degree of vulnerabili ty of P movement from the site. A weighting procedure has been develop ed to include the various contributions each site characteristic may h ave. A summation of the products of the weighted site characteristic y ields a site vulnerability rating. An assessment tool using the Phosph orus Index will assist field staff working with landusers to identify sensitive areas and recommend management alternatives to reduce risk o f P losses.