Analysis of nitrogen management strategies using EPIC
1998
Ramanarayanan, T.S. | Storm, D.E. | Smolen, M.D.
This paper illustrates a method of using a hydrologic/water quality model to analyze alternative management practices and recommend best management practices (BMPs) to reduce nitrate-nitrogen (NO3(-)-N) leaching losses. The study area for this research is Tipton, an agriculturally intensive area in southwest Oklahoma. We used Erosion Productivity Impact Calculator (EPIC), a field-scale hydrologic/water quality model, to analyze alternative agricultural management practices. The model was first validated using observed data from a cotton demonstration experiment conducted in the Tipton area. Following that, EPIC was used to simulate fertilizer response curves for cotton and wheat crops under irrigated and dryland conditions. From the fertilizer response functions (N-uptake and N-leaching), we established an optimum fertilizer application rate for each crop. Individual crop performances were then simulated at optimum fertilizer application rates and crop rotations for the Tipton area, which were selected based on three criteria: (a) minimum amount of NO3(-)-N leached, (b) minimum concentration of NO3(-)-N leached, and (c) maximum utilization of NO3(-)-N. Further we illustrate that by considering residual N from alfalfa as a credit to the following crop and crediting NO3(-)-N present in the irrigation water, it is possible to reduce further NO3(-)-N loss without affecting crop yield.
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