Biomass production of switchgrass in central South Dakota

Switchgrass (Panicum virgatum L.) has potential as feedstock for a cellulose-based biofuels industry in temperate steppe regions of the northern Great Plains. Therefore, our objectives were to determine: (i) patterns of biomass accumulation and optimum harvest times for an early maturing cultivar, Dacotah (origin 46 degrees N, 100 degrees W), and a later maturing cultivar, Cave-In-Rock (origin 37 degrees N, 88 degrees W), in central South Dakota (44 degrees N, 100 degrees W) and (ii) if variation in patterns of biomass accumulation were associated with variation in patterns of precipitation. Dacotah and Cave-In-Rock were no-till planted near Pierre, SD, on 6 Dec. 1999. Harvest dates were once per year during July, August, September, or October 2001 through 2004. Morphological development was determined in early, mid, and late summer 2004. Maximum biomass yields for Dacotah were obtained during July or August. Optimum harvest time for Cave-In-Rock was as late as September depending amount of summer precipitation. Biomass production of both cultivars was highly plastic, fluctuating > fivefold over a 4-yr period. Maximum annual biomass yields were from > 9 Mg ha(-1) to < 2 Mg ha(-1) for both cultivars. Variation in April through May precipitation explained > 90% of variation in maximum annual biomass production. The superior biomass yield potential of the putatively unadapted Cave-In-Rock compared with the putatively adapted Dacotah was only expressed during years when precipitation was > 75% of average.