Simulating the impacts of bio-fuel crop production on nonpoint source pollution in the Upper Mississippi River Basin

The perpetuation of current trend of growing more corn for ethanol is projected to further exacerbate water quality problems in the Upper Mississippi River Basin (URMB). Switchgrass with cellulosic ethanol potential which requires no or little fertilizers can be effective in reducing nonpoint source pollutants such as nitrate and sediments. In this study, the Soil and Water Assessment Tool model was applied to the UMRB to simulate and evaluate the impacts of two bio-fuel crops (corn and switchgrass) on nonpoint source pollution. High impact areas to which a large amount of pollutants are attributed were identified by simulating and analyzing nitrate outputs from 131 subbasins. Simulation results showed that growing switchgrass instead of corn could reduce nitrate yield by up to 71% (14 kg/ha) and sediments by up to 99% (5 t/ha). It is demonstrated that water quality in the UMRB can be significantly improved and meanwhile economic benefits can still be derived. The results of this study can assist in cost-benefit analysis and decision-making in environmental management in large-scale agricultural areas.