Impacts of Biofuel Induced Land Use Change on Daily, Seasonal, and Inter-Annual Evapotranspiration and Energy Balance Dynamics of the Southwestern U.S. Cotton Belt Region.

We are facing an unprecedented challenge in securing America’s energy future. To address this challenge, increased biofuel crop production is needed. Although first-generation biofuels like corn ethanol are available, second-generation biofuels are gaining importance because they don't directly compete with food production. Second-generation biofuels are made from the by-products of intensive agriculture or from less-intensive agriculture on more marginal lands. The Southwestern U.S. Cotton Belt can play a significant role in this effort through a change from more conventional crops (like continuous cotton) to second-generation biofuel feedstocks (biomass sorghum and perennial grasses). While we believe there would be environmental benefits associated with this change in land use, their exact nature and magnitude have not been investigated for this region. Our goal is to investigate the energy, water, carbon and greenhouse gas fluxes associated with this change. Our hypothesis is that these biofuel feedstock systems will reduce negative environmental effects associated with conventional cropping systems currently in the region, leading to more environmentally sound agricultural systems while supporting the goal of increased biofuel production. Eddy covariance flux towers were established in four representative land uses in the Southern Great Plains. Irrigated and dryland cotton (Gossypium hirsutum L.)) represent the major land use in region and high biomass forage sorghum (Sorghum bicolor L. Moench) and old world bluestem (Bothriochloa baldhii Retz S.T. Blake ) represents potential bioenergy crops. Continuous measurement of carbon, water and energy (latent, soil, and sensible heat) fluxes were made along with other meteorological variables including air temperature, relative humidity, photosynthetically active radiation, solar irradiance, net radiation, soil moisture etc. Results will quantify the effects of the increased adoption of alternate biofuel cropping systems on the hydrologic cycle of the semi-arid Southwestern Cotton Belt region and thereby provide sound information for assessing the potential impacts of this change in land use. Complete results will be presented at the meetings.