ABSTRACT:
The persistence of water quality problems has directed attention toward reduction of agricultural non-point sources of phosphorus (P). We assessed the practical impact of three manage merit scenarios of the USDA-EPA Strategy for Animal Feeding Operations to reduce P losses from a watershed. Using an agronomic threshold of 50 mg Mehlich-3 P kg−1 soil, 55% of our watershed would receive no P as fertilizer or manure. An environmental threshold of 190 mg Mehlich-3 P kg−1 soil, above which P loss in runoff increases, restricts future P inputs to less than crop removal on 32% of the watershed. Finally, a site assessment P index, which accounts for likely source and transport risks was used. This showed none of the watershed was at high risk of P loss and that areas of medium risk (where remedial measures should be considered) were near the stream channel. In the watershed studied, the P index was the best method to target remedial management to minimize P export and impacted less land area than the other strategies
Footnotes
Richard W. McDowell, Andrew N. Sharpley and Jennifer L. Weld are scientists with the U.S. Department of Agriculture-Agricultural Research Service's Pasture Systems and Watershed Management Research Unit in University Park, Pennsylvania. Doug B. Beegle is a scientist working in the ASI Building at Pennsylvania State University in University Park, Pennsylvania.
- Copyright 2001 by the Soil and Water Conservation Society
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