Submitted to: American Society of Agronomy Meetings
Publication Type: Proceedings
Publication Acceptance Date: July 1, 2000
Publication Date: November 1, 2000
Citation: Sharpley, A.N. 2000. Why we need environmental risk indices for p-based management. American Society of Agronomy Meetings. [CD-ROM] Technical Abstract: Inputs of Phorphorus (P) are essential for profitable crop and livestock production, however, P inputs to fresh waters can accelerate eutrophication. The intensification of farming systems has created surpluses of P in manure over crop needs and led states to develop P as well as N-based management recommendations. The initial use of soil P thresholds to accomplish this has been shown to be limited for several reasons: 1) although runoff P is related to soil P, recent applications of P can be overriding; 2) where a field is in a landscape can affect its relative contribution of P to channel export; 3) land management can affect soil P release and transport; and 4) a need to consider the affect of BMPs (conservation practices) on the potential for P loss. Fields at greatest risk of P loss are those where areas of high P application or soil P coincide with zones of active surface runoff or erosion. The P index was developed to account for these factors, while remaining easily understood and simple to use. Clearly, assessment of site vulnerability to P loss by the index is needed to identify fields or practices at greatest risk and to give farmers more flexibility in developing remedial strategies.