1. Identifying Critical Sources of Phosphorus Export from Agricultural Watersheds

Phosphorus (P) is an essential element for plant and animal growth, and its input to agriculture is necessary to maintain profitable crop and animal production. Eutrophication, the natural aging of lakes or streams brought on by nutrient enrichment, can be accelerated by P inputs to fresh waters from human activities (Carpenter et al., 1998; Schindler. 1977). Eutrophication has been identified as the main problem in surface waters withimpaired water quality (USEPA. 1996). It restricts water use for...