Effects of Naturally Occurring Drought on the Productivity of Miscanthus in Southeastern U.S.

Miscanthus (Miscanthus × giganteus) is a C4 perennial rhizomatous grass that is considered a promising lignocellulosic biomass feedstock for biofuel production. Miscanthus has the potential for greater biomass production and carbon uptake than maize or switchgrass, as well as the possibility of growing on degraded land; however, productivity depends on the relative availability of water, nutrients, and environmental suitability of the crops. In order to determine how miscanthus might perform in the Southeast, we evaluate the annual evapotranspiration, net carbon uptake and water use efficiency of miscanthus grown in a rainfed field near Tifton, Georgia, USA during the 2015 and 2016 growing seasons. CO2 and Latent Heat flux measurements are taken using an eddy-covariance system, part of the USDA Long Term Agroecosystem Research (LTAR) network. Annual evapotranspiration (ETc) for the rainfed miscanthus was estimated at 668.2 mm and the carbon net ecosystem exchange (NEE) at 3899 kg C/ha for a water use efficiency of 5.8 (NEE/ETc). These values are relatively low compared to reported miscanthus yields in the upper Midwest around 9000-12000 kgC/ha and WUE around 12-18.