ARS | Publication request: A regional comparison of water-use efficiency for Miscanthus x giganteus and Panicum virgatum

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: January 3, 2011
Publication Date: January 31, 2011
Citation: VanLoocke, A., Zeri, M., Twine, T.E., Bernacchi, C.J. 2011. A regional comparison of water-use efficiency for Miscanthus x giganteus and Panicum virgatum. AmeriFlux Science Meeting and 3rd NACP All Investigators Meeting. #D-83.

Technical Abstract: The production of second generation bioenergy feedstocks is likely to increase significantly over the coming decades. A key factor dictating the environmental impact/services of production is the trade-off between water-use and productivity (e.g., harvestable yield (HY) and net ecosystem carbon exchange (NEE)). For this study we focus on two candidate second generation feedstocks with marked differences in water use and productivity, Miscanthus x giganteus (miscanthus) and Panicum virgatum (switchgrass). The water-use efficiency is compared using two metrics: harvestable water-use efficiency (HWUE = evapotranspiration (ET) ET/HY), and ecosystem water-use efficiency (EWUE = ET/NEE). We developed and tested a new version of Agro-IBIS (Integrated Biosphere Simulator - agricultural version). Simulations of NEE and ET were evaluated against eddy covariance observations in plots located side-by-side at the University of Illinois Energy Farm. Then simulations were run with historic climate data to produce 30 year means for each land cover type for the Midwest U.S. Our analysis indicates that over the Midwest U.S. miscanthus has the highest HWUE (~25 kg ha-1 mm-1), followed by current crops (e.g. maize, soybean, and wheat; ~18 kg ha-1 mm-1) and switchgrass (~15 kg ha-1 mm-1). Miscanthus and switchgrass both have a higher EWUE than current crops; however, miscanthus has the potential to disrupt the hydrologic cycle as a result of higher evapotranspiration in drier areas (~700 mm yr-1), whereas switchgrass may have a smaller impact. The results of this analysis can be used to suggest locations for test plots and they highlight the need for observations of water-use and carbon exchange by potential feedstocks throughout the region.