CROP PRODUCTION SYSTEMS TO CONTROL EROSION AND REDUCE RUNOFF FROM UPLAND SILTY SOILS

摘要

Soil erosion remains the most significant threat to long-term agricultural sustainability. In order to determine if highly erodible silty upland soils could be row-cropped while conforming to the conservation provisions of the Food Security Act, we measured natural-rainfall runoff and soil loss for six years from eight alternative cropping systems on sixteen 4% slope plots and three small watersheds in north Mississippi. Several conservation cropping systems slightly reduced runoff and greatly decreased erosion on these soils. On erosion plots, no-till for soybean, corn, or sorghum reduced soil loss by more than 80% and no-till for cotton by more than 70% as compared to conventionally tilled soybean. Ridge-till was more than twice as erodible as no-till, while no-till soybean double-cropped with wheat was least erodible of the eight systems studied. On small watersheds, annual sediment yield ranged up to about 30 t/ha for conventional tillage soybean with buffer strips and grassed waterways but, after the first year, never exceeded 1 t/ha for no-till soybean. However, no-tillage alone was not adequate to control concentrated-flow headcuts. Most conservation systems decreased runoff by at least 10%. No-till sorghum or corn with a vetch cover crop generally decreased runoff most, and doublecropped soybean-wheat had less than 75% of the runoff of conventional soybean. Greatest reductions occurred during years of higher runoff amounts. Runoff per unit of area from the watersheds was much greater than from comparable erosion plots, indicating that extrapolation of plot data to field areas merits careful consideration of their relative soil and topographic characteristics. This research demonstrated that several no-tillage cropping systems can keep erosion below tolerable limits, reduce runoff somewhat, and be economically profitable. When combined with complementary conservation practices such as waterways and grass hedges, they provide methods for achieving both effective conservation and sustainable production when intensively cropping erodible upland soils of the southern United States.