Harvest and Nitrogen Management of Three Perennial Grasses as Biomass Feedstock in Subarctic Alaska
Keywords:biomass energy, harvest timing, nitrogen application rate, smooth bromegrass, tufted hairgrass, slender wheatgrass
High energy costs in high-latitude regions have generated interest in the feasibility of bioenergy cropping. The goal of this study was to determine the N response and best harvest regime for biomass production of three perennial, cool-season grass species—tufted hairgrass (Deschampsia caespitosa (L.) P. Beauv.), slender wheatgrass (Elymus trachycaulus (Link) Gould ex Shinners), and smooth bromegrass (Bromus inermis Leyss)—at two locations in central Alaska. Maximum dry matter yields were 11.3 Mg ha-1 for smooth bromegrass, 8.1 Mg ha-1 for tufted hairgrass, and 8.0 Mg ha-1 for slender wheatgrass, but yields varied greatly among years. We found a linear N response in most cases, with highest yields at the 100 kg N ha-1 application rate. Yields for the double-harvest regime usually did not vary significantly from those of the fall harvest, but spring harvest sometimes reduced yields dramatically. Biomass in the spring harvest was usually dry enough not to require additional drying for storage. Results of this study indicate it may be possible to produce grass biomass yields high enough for use as bioenergy feedstocks in central Alaska, but questions remain about the best management practices and the economics of growing bioenergy crops in Alaska.