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United States Department of Agriculture

Agricultural Research Service

Research Project: UNDERSTANDING AND PREDICTING THE IMPACT OF AGRICULTURE ON THE ENVIRONMENTAL INTEGRITY OF MANAGED WATERSHEDS

Location: Water Quality and Ecology Research

Title: Assessing long term impact of phosphorus fertilization on phosphorus loadings using AnnAGNPS

Authors
item Yuan, Yongping -
item Bingner, Ronald
item Locke, Martin
item Stafford, Jim -
item Theurer, Fred -

Submitted to: International Journal of Environmental Research and Public Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2011
Publication Date: June 14, 2011
Citation: Yuan, Y., Bingner, R.L., Locke, M.A., Stafford, J., Theurer, F.D. 2011. Assessing long term impact of phosphorus fertilization on phosphorus loadings using AnnAGNPS. International Journal of Environmental Research and Public Health. 8(6):2181-2199.

Interpretive Summary: The Maumee River Basin in Ohio is a highly productive agricultural region where potential water quality problems can occur as a result of high phosphorus losses transported by streams into Lake Erie. Agricultural management practices that can reduce nonpoint source pollution and improve water quality were evaluated in this study. Evaluations included effects of various phosphorus (P) fertilization rates on phosphorus losses within the Ohio Upper Auglaize watershed located in the southern portion of the Maumee River Basin using the USDA Annualized AGricultural Non-Point Source (AnnAGNPS) pollutant loading model. Results from the study indicate P loadings increase as fertilization rate increases, but long term high P application rates can lead to much higher P loadings leaving the watershed. This dramatic change of P loading to the watershed outlet indicates that a “critical point” may exist in the P levels in the soil where P loss transported by runoff water increases dramatically. This information is critical when implementing plans that include nutrient management practices and guidelines for agricultural watersheds by action agencies such as the USDA Natural Resources Conservation Service.

Technical Abstract: High phosphorus (P) loss from agricultural fields has been an environmental concern because of potential water quality problems in streams and lakes. To better understand the process of P loss and evaluate the different phosphorus fertilization rates on phosphorus losses, the USDA Annualized AGricultural Non-Point Source (AnnAGNPS) pollutant loading model was applied to the Ohio Upper Auglaize watershed located in the southern portion of the Maumee River Basin. In this study, the AnnAGNPS model was calibrated using USGS monitored data; and then the effects of different phosphorus fertilization rates on phosphorus loadings were assessed. It was found that P loadings increase as fertilization rate increases, and long term higher P application would lead to much higher P loadings to the watershed outlet. The P loadings to the watershed outlet have a dramatic change after some time with higher P application rate. This dramatic change of P loading to the watershed outlet indicates that a “critical point” may exist in the soil at which soil P loss to water changes dramatically. This finding seems to confirm the findings of others. Simulations with different initial soil P contents showed that the higher the initial soil P content is, the less time it takes to reach the “critical point” where P loadings to the watershed outlet changes dramatically. This finding may be useful in setting up future P application and management guidelines.

Last Modified: 8/21/2014
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