MODELING ANIMAL WASTE MANAGEMENT PRACTICES: IMPACTS ON BACTERIA LEVELS IN RUNOFF FROM AGRICULTURAL LANDS

Abstract

ABSTRACT Runoff from agricultural lands carrying microorganisms from livestock manure can contaminate the food and water supplies of both animals and humans. Planning and design of animal waste management practices, thus, becomes more important as livestock populations become more concentrated. A computer model is proposed to predict the effects of animal waste management practices on the bacteria concentration of runoff from agricultural lands. The model uses Monte Carlo simulation to combine the deterministic relationships with statistical knowledge concerning rainfall and temperature variation. The model outputs maximum and minimum bacteria concentrations in runoff resulting from a storm assumed to occur immediately after manure is applied to the land. The model can simulate the effects of waste storage, filter strips, and incorporation of manure into the soil. Data and information collected from the Owl Run watershed in Fauquier County, Virginia is used to demonstrate the model's applicability and potential. Long-term manure storage was found to be the most appropriate practice for reducing bacteria concentrations for the study site. Incorporation of manure was as effective as long-term storage, but is more costly. Buffer strips alone were not sufficient for reducing bacteria concentrations to meet the water quality goal. Since animal waste management practices have only recently been implemented on the watershed, no field data is yet available to validate the model's predictions.