Corn and Soybean Cropping Effects on Soil Losses and C Factors

Greater soil losses are generally thought to occur with soybean (Glycine max. (L.) Merr.) cropping than with corn (Zea mays L.) cropping. However, runoff and soil losses from corn and soybean cropping systems have been measured simultaneously in only a few studies. The objectives of our study were to evaluate differences in soil and water losses between continuous corn and continuous soybean cropping for conventional, field cutivation, and no-till methods of tillage; and to evaluate differences between measured cropping and management (C) factors and those in Agricultural Handbook 537, USDA that are currently used in soil conservation planning. These objectives were accomplished by analyzing soil and water loss data from a 7-yr study conducted on a claypan soil in central Missouri. Cropping differences were evaluated for five seasonal periods based upon cultural operation dates and estimated amounts of canopy cover. Average annual soil loss from soybeans was significantly higher (p less than 0.01) than that of corn for the conventional and no-till methods. Seasonal periods having the greatest cropping differences in soil loss were period F (rough fallow), period 12(30 to 60 d after planting) and period 4 (fall harvest to spring tillage). Annual C factors for soybeans were aboutmore » two times those of corn for all tillage methods. Measured C factors for all tillage methods were consistently lower than those presented in Agricultural Handbook 537, USDA.« less