Water Quality Effects of Corn Stover Removal for Cellulosic Ethanol Production.

Corn stover has been identified as a prime feedstock for large-scale cellulosic ethanol production. Recent climate change legislation in the U.S. has created an incentive for the agricultural sector to provide bio-energy feedstock. Therefore, understanding the impacts of widespread stover harvest on soil and environment is needed to establish soil-specific stover removal rates. We assessed the effects of variable levels of corn stover removal on runoff and soil erosion on a regional scale across three locations (Colby, Hugoton, and Ottawa) in Kansas under a strong east-west precipitation gradient. Five stover treatments that consisted of removing 0, 25, 50, 75, and 100% of corn stover after harvest were studied for losses of runoff, sediment, sediment-associated soil organic carbon (SOC), total N and P, NO₃-N, NH₄-N, and PO₄-P. Simulated rainfall at a rate of 76.2 mm h^-1 in Colby and Hugoton, and 91.4 mm h^-1in Ottawa was applied for 30 min, which represents a 5-yr return period for each site.  Results of this regional study showed that runoff volume, SOC, and total N and P concentrations increased with increase in stover removal at all locations. In contrast, NO₃-N, NH₄-N, and PO₄-P concentrations in runoff increased with decrease in stover removal rate, most likely due to nutrient leaching from stover. Our results suggest that high rates of stover removal for cellulosic ethanol production will increase sediment, sediment-associated SOC, and total nutrient loss in runoff, potentially increasing risks of water pollution and soil degradation.