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Title: Evaluation of phosphorus site assessment tools: lessons from the USA

Author
item SHARPLEY, ANDREW - University Of Arkansas
item Kleinman, Peter
item Baffaut, Claire
item BEEGLE, DOUG - Pennsylvania State University
item Bolster, Carl
item COLLICK, AMY - University Of Maryland Eastern Shore (UMES)
item EASTON, ZACHARY - Virginia Tech
item LORY, JOHN - Missouri State University
item NELSON, NATHAN - Kansas State University
item OSMOND, DEANNA - North Carolina State University
item RADCLIFFE, DAVID - University Of Georgia
item Veith, Tameria - Tamie
item WELD, JENNIFER - Pennsylvania State University

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2017
Publication Date: 8/3/2017
Citation: Sharpley, A., Kleinman, P.J., Baffaut, C., Beegle, D., Bolster, C.H., Collick, A., Easton, Z., Lory, J., Nelson, N., Osmond, D., Radcliffe, D., Veith, T.L., Weld, J. 2017. Evaluation of phosphorus site assessment tools: lessons from the USA. Journal of Environmental Quality. doi: 10.2134/jeq2016.11.0427.

Interpretive Summary: The P Index has been one of the major tools used in nutrient management across the US, but there has been only patchy testing of it. Coordinated projects were carried out in major US regions to test the different P Indices of those regions. Computational modeling was needed to fully evaluate the P Index, but was hampered by the limitations of most models. Ultimately, opportunities were identified to update existing P Indices.

Technical Abstract: Critical source area identification through phosphorus (P) site assessment is a fundamental part of modern nutrient management planning in the U.S. To date, the P Index has been the primary tool for P site assessment adopted by US states, but there has been only patchy testing of the many versions of the P Index that now exist. Verification of P site assessment tools is extremely difficult as they are expected to apply to any field conditions found in the geographic areas where they are implemented. In general, verification with in-field monitoring data has been limited, focused primarily on corroborating manure and fertilizer “source” factors. In some cases, verification efforts have used fate and transport models to produce water quality data to compare with P Index ratings. Elsewhere, versions of these models have been proposed as alternatives to the P Index (i.e., APEX, APLE, SWAT and TBET). While there are limitations in the capability of fate-and-transport models to simulate the effects of nutrient management on P runoff, hydrology is often more accurately predicted with these models than with P Indices. Even so, carefully crafted regional approaches can be used to improve the application of fate-and-transport models to sites where they have not been specifically calibrated. While regional approaches to P site assessment can be justified through closely coordinated efforts that engage science, policy, and implementation communities, poor precedent exists, however, for uniform national P site assessment tools.