Biomass and Morphological Development of Miscanthus Compared with Native Grass in South Dakota

Little is known about Miscanthus for bioenergy in the northern Great Plains. This study compared 10-year-old stands of Miscanthus x giganteus to switchgrass (Panicum virgatum L.) and prairie cordgrass (Spartina pectinata Link) for biomass on marginal cropland in eastern South Dakota. This study was conducted during 2017 and 2018 at Brookings, SD. Day of year (DOY), species, and N fertility were evaluated for effects on biomass yield and related components (tillers m-2, plant height, and weed biomass). All three variables had significant effects on biomass yield, tiller m-2, and tiller height in both years. N rate had no effect on weed biomass. Effect of N was most notable for M. x giganteus. Biomass yields of fertilized M. x giganteus, prairie cordgrass and switchgrass were 1.7 times that of unfertilized. Biomass distribution among phytomers was determined for Miscanthus in June, July, August, and September. At end of growing season about 40% of the total biomass yield was in the five most proximal phytomers. The most distal four phytomers remained undeveloped due to killing frost. Biomass was estimated in April 2018 and 2019 from stockpiled over-wintered growth at Brookings, SD. The design was a split-plot with species whole plots and N fertilizer (0 or 112 kg N per ha) sub-plots. Species and N rate were significant in both years. In 2017, biomass yield was from 15.7 Mg per ha for Miscanthus to 9.4 Mg per ha for switchgrass. Fertilized produced 80% more biomass than unfertilized plots. The species x N rate mean square was significant in 2017, with Miscanthus having a much greater response to N than the other grasses. No difference was found among species at 0 kg N ha-1, whereas species means were significant at 112 kg N ha-1. In 2018, Miscanthus (12.9 Mg ha-1) and prairie cordgrass (12.3 Mg ha-1) produced more than switchgrass (5.5 Mg ha-1). Miscanthus produced large amounts of cellulosic biomass, compared to native grasses in the NGP; however, its superiority was only at a high level of N, a costly input for sustainable biofuel production systems