Effect of fall tillage following soybeans on organic matter losses in snowmelt

In a corn-soybean rotation, maintaining crop residue on the soil surface is a challenge following soybeans. Often farmers are encouraged not to till the soil following a soybean crop in order to maximize the amount of residue at the soil surface. In this study we evaluated the effect of this practice compared to fall moldboard plowing on snowmelt runoff and losses of total solids (TS) and organic carbon (using oxygen demand in runoff as a surrogate). A paired watershed approach was used to evaluate the effect of these management practices. Individual hydrographs were compared and contaminant losses in runoff calculated. Results show that snowmelt runoff and the associated losses of total solids, chemical oxygen demand (COD), and biochemical oxygen demand (BOD) were less with fall moldboard plowing compared to no fall tillage following soybean (0.22 cm, 1.9 kg ha^-1, 0.81 kg ha^-1, 74 g ha ^-1, reduction in median value per melt cycle, respectively). In areas where snowmelt runoff is an important component of annual runoff, some tillage in the fall would be preferable to no-tillage in order to reduce snowmelt runoff losses.