Effect of Corn Stover Removal Rate and Biochar Addition on Soil and Nutrient Losses in Surface Runoff.

The removal of crop residues for biofuel production and other uses can negatively affect soil structure resulting in reduced aggregate stability and reduced infiltration, which can lead to increased soil erosion and soil and water degradation. The magnitude of these effects probably varies with soil type and tillage practice as well as the amount of residue removed. Therefore, we used rainfall simulation at field plots in Ames, IA and Morris, MN to investigate the effect of tillage and corn stover removal on soil and nutrient loss in surface runoff.  Approximately 70 mm of simulated rainfall was applied to 1.5 by 3.0 plots in 60 min. Chisel-tilled and no-till plots in Iowa were in continuous corn production and corn stover was removed annually at 0, 50, and 100% rates. An additional set of tilled plots received biochar to compensate for residue removal.  Runoff, sediment, and nutrient losses were consistently less from the no-till plots with 0% residue removal than from any other tillage/residue removal combination.  Residue removal from the no-till plots increased runoff, sediment, and nutrient losses, but the differences among the 50 and 100% removal rates were small and inconsistent. The rate of residue removal from the chisel-tilled plots did not have a consistent effect on runoff or sediment and nutrient losses, suggesting that the effect of tillage was much greater than the effect of residue removal and that biochar addition did not affect these losses.