ABSTRACT
Phosphorus (P), an essential nutrient for crop and animal production, can accelerate freshwater eutrophication, which is the most ubiquitous water quality impairment in the U.S., with agriculture a major contributor of P (Sharpley 2000; U.S. Geological Survey 1999). Environmental concerns from harmful algal bloom outbreaks
(Burkholder and Glasgow 1997) and regulatory pressure to reduce P loadings to surface waters via implementation of Total Maximum Daily Loads (TMDLs) (U.S. Environmental Protection Agency 2000) have increased the urgency for information on the impacts of agricultural management, specifically conservation practices and best management practices (BMPs) on P loss. Because of the time and expense involved in assessing P loss, models are often a more efficient and feasible means of evaluating management alternatives. In their most comprehensive form, models can integrate information over a watershed scale to identify BMPs and critical source areas where BMPs are most likely to affect watershed-scale P losses.
