While phosphorus (P) is essential for profitable crop and livestock agriculture, its loss in watershed runoff accelerates eutrophication of receiving surface waters. The best management practices (BMPs) to mitigate P transfers to surface water include soil and water conservation practices, other management techniques, and social actions appropriate for specific agronomic, environmental, and socioeconomic conditions. Source BMPs are designed to minimize P available to runoff and reduce farm P imports by changing animal feed rations or adding feed additives that increase livestock P-use efficiency.
Source BMPs also involve treating manure to lower its soluble P content, managing soil P levels, moving manure from surplus to deficit areas, and finding alternative uses for it other than land application. Transport BMPs are designed to limit runoff, erosion, and leaching as important pathways of P loss. These include such practices as conservation tillage, terracing, and stream buffers.
When implementing BMPs, it is critical that the most appropriate BMP, or suite of BMPs, be selected, targeted, and implemented in a watershed, while following recommended installation and maintenance guidelines. Because source and transport BMPs do not address the main problem of farm and regional P surpluses, long-term solutions must extend beyond the farm gate. Advances in crop and livestock breeding, feed processing, and manure utilization hold promise. Also, since many BMPs involve costs and management changes, which will most likely have negative impacts on farm income, fair and equitable financial support and technical assistance through cost-share programs will improve BMP adoption.