Comparisons of Switchgrass and Corn for Biomass and Bioenergy Under Irrigation.

An irrigated six-year field study compared biomass production from ten switchgrass cultivars with one corn hybrid at Washington State University, Prosser, WA. Switchgrasses were harvested twice per growing season while corn was harvested for silage at 50% milk-line and grain at black-layer each year. Biomass samples were scanned by NIRS. Switchgrass yields were lower than corn for the first two years. At the third production year Alamo and Kanlow yielded greater than corn silage. However, winter injury reduced switchgrass yields for most cultivars in year four. During this period crop experienced a three-year period of cooler than normal spring temperatures which reduce silage corn yields. Higher yielding switchgrass cultivar biomass yields during the final three years were equal to or greater than corn. Six-year silage corn yield averaged 24.0 Mg ha ^-1 while Alamo and Kanlow averaged 18.9 and 22.7 Mg ha ^-1 , resp. Bioenergy of switchgrass is higher when harvested in July compared to October. There are also differences among switchgrass cultivars for bioenergy with some lower yielding switchgrasses yielding higher bioenergy concentrations but not on a land area basis.