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Assessing Long Term Impact of Phosphorus Fertilization on Phosphorus Loadings Using AnnAGNPS
Citation:
YUAN, Y., R. L. Bingner, M. A. Locke, J. Stafford, AND F. D. Theurer. Assessing Long Term Impact of Phosphorus Fertilization on Phosphorus Loadings Using AnnAGNPS. International Journal of Environmental Research and Public Health. Molecular Diversity Preservation International, Basel, Switzerland, 8(6):2181-2199, (2011).
Impact/Purpose:
Phosphorus (P) is an essential nutrient for all life forms. Research has shown that a deficiency of P in soils limits crop production (Maples and Heogh, 1973), whereas higher levels of P in soils often lead to loss via surface runoff (Sharpley, 1995; Sharpley et al., 1996; Pote et al., 1996, 1999). Phosphorus losses to surface waters are of great concern on both national and regional scales because an abundance of P in fresh water will lead to algal blooms, which have many detrimental effects on natural ecosystems. Scientists have concluded that large areas of hypoxia in the northern Gulf of Mexico are due to excessive nutrients derived primarily from agricultural runoff via the Mississippi River (Rabalais et al., 1996, 1999; Aulenbach et al., 2007; USEPA, 2007). Excessive P is also responsible for algal blooms and associated water quality problems in Lake Erie of the great lake systems in Northern Ohio (Ohio EPA, 2008). Odors and discoloration caused by decay of algae interfere with recreational and aesthetic water use, algae blooms shade submerged aquatic vegetation and reduce or eliminate photosynthesis and productivity, and algae may clog water treatment plant filters (Sharpley et al., 1994).
Description:
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.