ARS | Publication request: Water use efficiency by switchgrass compared to a native grass or a native grass alfalfa mixture

Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 13, 2012
Publication Date: January 15, 2013
Citation: Hendrickson, J.R., Schmer, M.R., Sanderson, M.A. 2013. Water use efficiency by switchgrass compared to a native grass or a native grass alfalfa mixture. BioEnergy Research. DOI:10.1007/s12155-012-9290-3.

Interpretive Summary: Developing sustainable bioenergy systems requires understanding water use efficiency of perennial bioenergy crops, especially in semi-arid regions. We compared water use efficiency of a suggested cellulosic biofuel crop, switchgrass, with a dominant native perennial grass, western wheatgrass and a western wheatgrass-alfalfa mixture. We found that the water use efficiency of switchgrass was 3 to 4 times higher than western wheatgrass but including alfalfa with the western wheatgrass would improve water use efficiency. However, switchgrass depleted the soil water to a greater extend to produce biomass than did western wheatgrass or the mixture. This suggests that switchgrass is an appropriate biofuel crop for semi-arid regions based on its water use efficiency but its depletion of stored soil water may be a concern during multi-year droughts.

Technical Abstract: Development of sustainable cellulosic biofuel systems requires knowing the water use efficiency (WUE) of potential bioenergy crops. Impact of early and late season droughts on WUE and soil water deficits were evaluated in switchgrass (Panicum virgatum L.), western wheatgrass (Pascopyrum smithii (Rydb.) Á. Löve), and a western wheatgrass-alfalfa (Medicago sativa L.) mixture using a rain out shelter. Switchgrass WUE ranged from 5.6 to 7.4 g biomass mm-1 water used while western wheatgrass WUE was 1.06 to 2.07 g biomass mm-1 water used. Soil water deficit for the western wheatgrass-alfalfa mixture was lower than western wheatgrass or switchgrass under early drought while switchgrass had a greater water deficit than western wheatgrass or the western wheatgrass-alfalfa mixture (P <0.001) under late drought. Switchgrass had greater WUE suggesting it is appropriate for semi-arid regions but its greater soil water depletion compared to the other treatments would be a concern under multi-year drought conditions.