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United States Department of Agriculture

Agricultural Research Service

Research Project: POULTRY MANURE MANAGEMENT STRATEGIES TO REDUCE NON-POINT SOURCE PHOSPHORUS POLLUTION Title: Comparing Southern Phosphorus Indices

Authors
item Osmond, D - NCSU
item Cabrera, M - UNIV OF GEORGIA
item Feagley, S - TEXAS A&M
item Hardee, G - USDA/NRCS
item Mitchell, C - AUBURN UNIV
item Moore, Philip
item Mylavarapu, R - UNIV OF FLORIDA
item Oldham, J - MISSISSIPPI STATE
item Thom, W - UNIV OF KENTUCKY
item Walker, F - UNIV OF TENN
item Zhang, H - OK STATE UNIV

Submitted to: Journal of Soil and Water Conservation Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 2006
Publication Date: November 1, 2006
Citation: Osmond, D., Cabrera, M., Feagley, S., Hardee, G., Mitchell, C., Moore Jr, P.A., Mylavarapu, R., Oldham, J., Thom, W., Walker, F., Zhang, H. 2006. Comparing southern phosphorus indices. Journal of Soil and Water Conservation Society. 61:325-337.

Interpretive Summary: The U.S. Department of Agricultural updated the nutrient management policy in 1999 so that states must choose one of three ways to develop nutrient management plans for fields fertilized with animal manure; (1) base applications on crop P needs, (2) develop a threshold for soil test P threshold above which manure could not be applied, or (3) use a Phosphorus Index. Most states developed a Phosphorus Index. The objective of this paper was to compare P index ratings from southern states (AL, AR, FL, GA, KY, LA, MS, NC, OK, SC, TN, and TX). Most of the states developed qualitative indices (i.e. - the P index gives a relative risk of P runoff). Three states (AR, GA and NC) developed quantitative P Indices that actually calculate P runoff losses. All of the states surveyed in the south use a low, medium, high and very high rating class, with the same management implications that were outlined in the Federal NRCS 590 standard, except for TX. Texas uses 1x crop removal of P for impaired water body segment and 1.5x crop removal for non-impaired water bodies. Only two states (AR and TX) verified their indices against experimental data (i.e. - determine if the P index accurately predicts the risk of P runoff). This study helps identify similarities and differences between P indices across state boundaries and should help states when revising P indices in the future.

Technical Abstract: The USDA/NRCS updated the 590 nutrient management policy in 1999 so that states must choose one of three ways to develop nutrient management plans for fields fertilized with animal manure; (1) base applications on the agronomic P needs of the crop, (2) set an environmental soil test P threshold above which manure could not be applied, or (3) use a P index. Most states opted to develop a P index. The objective of this paper was to compare P index ratings from southern states (AL, AR, FL, GA, KY, LA, MS, NC, OK, SC, TN, and TX). Most of the states developed qualitative indices, however, AR, GA and NC developed quantitative P Indices that calculate P runoff losses. All states use a low, medium, high and very high rating class, with the same management implications that were outlined in the Federal NRCS 590 standard, except for Texas, which uses 1x crop removal of P for impaired water body segment and 1.5x crop removal for non-impaired water bodies. The only two states which have verified their indices against experimental data are AR and TX. The only southern state to conduct a sensitivity analysis on their index is NC. This study helps identify similarities and differences between P indices across state boundaries and should help states when revising P indices in the future.

Last Modified: 11/27/2014
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