Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/13/1996
Publication Date: N/A
Interpretive Summary: Agriculture is often pointed to as a major contributor to non-point source pollutants such as sediment and nutrients. In an attempt to conserve the natural resource base and combat non-point source pollution, the agricultural community has adopted methods of reduced tillage for managing their land. However, the ability to quantify the benefits of these methodologies is difficult. Computer modeling offers one means of quantifying the benefits from reduced tillage farming. The EPIC simulation model was used to reproduce measured runoff, sediment loss, and nitrate loss over a five year period from small watersheds located in the Blackland Prairie of Central Texas. EPIC was able to reproduce the measured results with efficiencies averaging 0.75 for both no-till and conventional tilled systems. The proved ability of EPIC to simulate conservation tillages on shrinking and swelling soils will give farm level managers and planners a tool for quantifying the benefits of conservation tillage.
Technical Abstract: An agricultural field scale simulation model (EPIC) was calibrated and validated to predict surface runoff, sediment yield, and nutrient transport from six small watersheds located in Riesel, Texas. Management practices included no-till and conventional till systems. Predicted parameter values were compared with measured data. Simulated monthly surface runoff was validated with efficiencies ranging from 0.73-0.81 for both no-till (NT) and conventional till (CT) systems. Simulated annual average soil loss and soluble nitrate loss were comparable with measured values. Monthly simulation of sediment and nitrate loss through surface runoff were impaired by model limitations. Validation of EPICs surface hydrologic component will provide environmental entities a tool for long- term decision making and evaluation of farm level management practices on sediment and nutrient loading to streams and waterways.