Submitted to: Agricultural Research Service Publication
Publication Type: Government Publication
Publication Acceptance Date: 9/8/2003
Publication Date: 7/20/2006
Citation: Sharpley, A.N., Daniel, T., Gibson, G., Bundy, L., Cabrera, M., Sims, T., Stevens, R., Lemunyon, J., Kleinman, P.J., Parry, R. 2006. Best management practices to minimize agricultural phosphorus impacts on water quality. Agricultural Research Service Publication. 52 p. Interpretive Summary: Phosphorus is an essential element required for crop production and is the primary agent controlling freshwater eutrophication, the process of organic enrichment of water bodies that is the most ubiquitous water quality impairment in the U.S. today. Although great strides have been made to control point source discharges of phosphorus, non-point sources of phosphorus have been primarily ignored, greatly due to the difficulty in their identification and control. While there is a great deal of information available on non-point source control measures or Best Management Practices (BMPs) in technical journals and reports, no attempt has been made to draw this information together into a practical guide for land resource managers. This fragmentation of information has led to many misconceptions on what constitutes an effective BMP for soil and water quality, and is limiting the ability of action agencies to develop and implement sustainable nutrient management programs for agricultural phosphorus. This informational booklet will be the first to pull this information together in one convenient semi-technical source for practical application and provide information on the benefits of BMPs for non-point loss phosphorus reduction. Without a scientific basis, many BMPs may not get the support needed to ensure their adoption and maintenance. Thus those charged with overseeing sustainable nutrient planning will be able to use this publication to develop and implement BMPs that protect soil and water resources.
Technical Abstract: Agricultural systems, particularly those involving livestock operations, are under increasing scrutiny as to their role in the degradation of surface water quality. Although inputs of P are essential for profitable crop and livestock agriculture, its export in watershed runoff can accelerate the eutrophication of receiving fresh waters. The rapid growth and intensification of crop and livestock farming in many areas has created regional surpluses of P, where inputs in feed and fertilizer exceed output in farm produce and in many areas, has increased P loss in watershed runoff. The overall goal of efforts to reduce P losses from agriculture to water should be to increase P use-efficiency by attempting to balance inputs of P in feed and fertilizer into a watershed with output in crop and livestock produce together with managing applications to soil. Short-term measures to reduce P loss in runoff use specific BMPs that address a variety of source and transport management measures. Source management seeks to reduce P inputs through balancing animal feed rations, using feed additives to increase P utilization by the animal, reducing soluble P in manure, targeting P application to soils with high retention capacities, managing soil P levels, moving manure from surplus to deficit areas, and finding alternative uses for manure than land application. Transport controls employ an understanding of loss or transfer mechanisms to avoid P application on areas with a high transport potential. Also, the potential for P transport can be reduced by implementation of conservation practices such as reduced tillage, terracing, and stream buffers. This publication briefly outlines those factors affecting agricultural P loss and details management options and on-farm conservation practices that can be directed at controlling non-point sources of agricultural P.