Document Type

Technical Report

Publication Date



Agriculture, Model studies, Nutrients, Water quality control, Water quality modeling


Approximately one million Mg of broiler litter were generated in conjunction with Arkansas' 1989 broiler production. Common practices for disposal of the waste have the potential to damage the quality of downstream rivers and lakes. This possibility is enhanced due to the concentration of broiler production in areas of the state with shallow soils, steep slopes, and limited suitable disposal area. Since the risk of pollution is greatest immediately following disposal and increases with rainfall depth and intensity, adverse water quality impacts may be mitigated by timing the application to coincide with low probability of surface losses of the nutrients responsible for eutrophication. The objective of this research was to identify the time of year which is optimal, in terms of surface water quality, for disposal of broiler litter under Arkansas conditions. This objective was accomplished by using the Erosion Productivity Impact Calculator (EPIC) model to simulate water quality impacts of land-applied broiler litter as a function primarily of weather variables. Nutrient losses were simulated for long periods using varying application dates. Output from the simulations was used to establish the relationship between application date and average nutrient losses, enabling the identification of optimal timing of disposal. The procedure was replicated for three areas of the state in order to characterize spatial variability in optimal timing of disposal. The results indicate that there exist "windows" within which waste application can minimize nutrient losses and maximize grass yields. These windows, however, vary depending on the parameter of interest and the location being simulated.

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