RUNOFF AND SEDIMENT YIELD FROM A FLATLAND WATERSHED IN SOYBEANS

ABSTRACT Runoff and sediment yield data from soybeans on a flatland watershed in the Mississippi Delta support results of earlier studies using cotton which conclude that soil erosion is a serious problem in this region. Average annual sediment yield from a 15.6-ha Mississippi Delta watershed in conventional-till soybeans during a six-year (1979-1984) period was 11.1 t/ha. Cropland was graded to a furrow slope of 0.2% slope with rows in a north-south direction. Mean row length was 186 m. Conventional-till cotton had been grown on the watershed for many years preceding this study. Tillage during the cotton study was more intensive than that during the soybean study, and contributed to higher sediment yields during the cotton study. Sediment yield averaged 29 t/ha per year during a two-year period (1972-1973) under conventional-till cotton under high rainfall and 14 t/ha per year for the succeeding five-year period (1974-1978) under more normal rainfall. KEYWORDS. Watershed, Flatlands, Mississippi delta. Runoff, Sediment yield. Soybeans.