ARS | Publication request: TESTING THE PHOSPHORUS INDEX IN AN AGRICULTURAL WATERSHED IN PENNSYLVANIA

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., Gburek, W.J., Beegle, D., Kleinman, P.J. 2000. Testing the phosphorus index in an agricultural watershed in pennsylvania. American Society of Agronomy Meetings. [CD-ROM].

Technical Abstract: Acceleration of freshwater eutrophication by Phosphorus (P) has forced several states to develop management recommendations based on the potential for P loss in agricultural runoff. In response, an index has been developed to rank field vulnerability to P loss so that high risk areas may be identified for rsite-specific management. Although research has justified transport (erosion, runoff, leaching, landscape position) and source factors (added fertilizer and manure, soil P) in the P index, there has been little field- scale evaluation. Using a portable rainfall simulator, we measured dissolved P loss in runoff from fifty 2 by 1 m plots within a Pennsylvania watershed and compared these losses with P index ratings calculated for each plot site. For all plots, runoff dissolved P was not related to Mehlich-3 soil P (r of 0.43) due to the fact that about half the sites were ein recently manured fields (<4 weeks prior to rainfall simulation), which overrode soil P effects. However, P index ratings for each plot location were closely related to runoff dissolved P (r of 0.88). This field-scale evaluation indicates the P index can accurately account for and describe a site's potential for P loss if runoff were to occur.