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United States Department of Agriculture

Agricultural Research Service

Research Project: Efficient Management and Use of Animal Manure to Protect Human Health and Environmental Quality

Location: Food Animal Environmental Systems Research

Title: Technical guidance for assessing phosphorus indices)

item Sharpley, Andrew
item Bolster, Carl
item Conover, Caitlin
item Dayton, Elizabeth
item Davis, John
item Easton, Zach
item Good, Laura
item Gross, Chris
item Kleinman, Peter
item Mallinaro, Antonio
item Moffitt, David
item Nelson, Nathan
item Norfleet, Lee
item Osmond, Deanna
item Perry, Roberta
item Thompson, Anita
item Vadas, Peter
item White, Michael

Submitted to: SERA-IEG 17 Bulletin
Publication Type: Other
Publication Acceptance Date: 1/3/2013
Publication Date: 1/15/2013
Citation: Sharpley, A., Bolster, C.H., Conover, C., Dayton, E., Davis, J., Easton, Z., Good, L., Gross, C., Kleinman, P., Mallinaro, A., Moffitt, D., Nelson, N., Norfleet, L., Osmond, D., Perry, R., Thompson, A., Vadas, P.A., White, M.J. 2013. Technical guidance for assessing phosphorus indices. SERA-IEG 17 Bulletin. 417:78.

Interpretive Summary:

Technical Abstract: Disparate nutrient and land management recommendations generated by P Indices among states, a perceived lack of change in P-based management, and persistent P loading problems in many of the nation’s waters, led to a revision of the 590 Standard. The revision requires an assessment of P Indices across the U.S. to ensure that each state Index is correctly ranking the potential for P delivery to surface water. This report describes the rationale behind P Index assessment, how assessment should be conducted, what data and models should be used, and how assessments may be interpreted and incorporated into P Index revisions. At the end of 2012, NRCS funded six CIG to assess P Indices across the U.S. This report does not review their objectives, but provides as Appendices 1, 2, and 3, regional CIG methodologies and ongoing NRCS P Index assessments using APEX. The overarching intent of assessing Indices is to ensure they appropriately rank risk of actual P loss for any given site relative to other sites; are directionally and magnitudinally correct, in that as factors influencing P loss change to increase or reduce that loss, P Indices correctly estimate the extent of change in P loss; interpretations based on assigned risk are equivalent across state borders, given similar site and water resource conditions; and where inadequacies exist, the causes can be identified and rectified. The main recommendations are; • Runoff monitoring data are required to build confidence in P Index representation of site P loss potential, as well as validate nonpoint source models. Databases should include at a minimum runoff, site conditions, climate, management, and P loss over the planning / rotation period under natural rainfall. • Several models are available, such as APEX, APLE, and DrainMod. • Baseline management scenarios must be developed, against which to compare Index performance and source and transport factors influencing P loss ranked as locally-relevant low, medium, and high loss. • Conditions must be defined that result in both unacceptable P loss within a model and high P Index ratings that limit or preclude P applications run under the same set of conditions. • Determination of uncertainty or variability of Indexed risk and P loss is recommended.

Last Modified: 8/24/2016
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