Biofuel Cropping System Effects On Soil Moisture and Inorganic Nitrogen Leaching in Central Illinois.

Utilizing perennial crops for biofuel production in tile drained regions could greatly alter water and nitrogen budgets in ways that might improve water quality and reduce spring time flooding, but harm aquatic life during low flow periods. In an effort to evaluate bioenergy production potential and environmental impacts of perennial crops Miscanthus x Gigantus and switchgrass, we measured soil moisture and inorganic N leaching from corn, soybeans, Miscanthus and switchgrass during 2005-08 at the University of Illinois. During the growing seasons, soil water content was measured two to three times per week at 10 cm depth intervals to a depth of one meter. Inorganic N fluxes (nitrate and ammonium) were assessed using resin lysimeters buried at a depth of 50cm.  Soil water content was less in the biomass plots compared to corn or soybeans during the early growing season. At the end of the growing season, soil moisture under Miscanthus was much lower than all other crops.  Combined nitrate and ammonium leaching from corn or soybeans was 35 to 50 kg N ha^-1 yr^-1 compared to <10 kg N ha^-1 yr^-1 from the biomass crops. Most of this difference was due to very high nitrate leaching from corn and soybeans, and minimal nitrate leaching from the perennial crops. The results to date suggest that widespread conversion of tile drained land from corn-soybean production to perennial crops would greatly decrease inorganic N leaching losses to surface waters. Additionally, perennial crops would reduce soil moisture during the spring which could reduce flood flows during that time. The increased water use by Miscanthus late in the growing season is more likely to extend the duration and severity of low flow periods in the late summer and fall, which could have negative consequences for water supplies and aquatic organisms.