Adoption of Miscanthus Cultivation On US Croplands: Impact On Soil Carbon and Water Resources.

Cellulosic biofuels are projected to be deployed at large spatial scales in order to meet U.S. national energy goals. However, little is known about the impact of such an expansion on soil organic carbon (SOC) pools and water resources. This study addresses these impacts by modeling Miscanthus productivity for continental US croplands using the Miscanmod physiological model.  Miscanmod uses growing degree days, incoming solar radiation, minimum and maximum temperatures, and empirical characteristics of the Miscanthus crop in order to predict the productivity of biomass under given conditions. Productivity for harvestable biomass ranged from 11.7 to 26.1 Mg ha^-1 yr^-1, with a spatial average of 19 Mg ha^-1 yr^-1 and a coefficient of variation of 13%. This variation resulted primarily from spatial heterogeneity of growing degree days and solar radiation interception. Using root to shoot ratio and mineralization constant, the underground biomass contribution from Miscanthus to SOC will be estimated for a 10% conversion of US croplands under field crop cultivation to Miscanthus production for biofuel. Productivity predictions along with the effective rainfall estimates, are then used to project areas in which Miscanthus can be optimally cultivated as a rainfed crop as well as those where it would require additional irrigation in order to meet crop water demand. The results will suggest the potential impact of Miscanthus crop adoption on SOC and water.