Direct Comparison of Biomass Yields of Annual and Perennial Biofuel Crops.

Increasing demand for renewable fuel sources has stimulated the need for alternative biomass crop production. This study was conducted to determine total biomass yields of annual and perennial feedstock crops produced at two locations in Northeast Kansas.  In 2007, randomized complete block plots were established in Manhattan, KS on Ivan, Kennebec, Kahola, Reading silt loam soils and at Troy, KS on a Kennebec silt loam. The study consisted of corn (Zea mays L.) grown continuously and rotated with soybeans (Glyzine max (L.) Merr.), five sorghum (Sorghum bicolor (L.) Moench) varieties; brown mid-rib (BMR), photoperiod sensitive (PS), sweet sorghum, and two forage/grain sorghums, rotated with soybeans, and three annual warm season grasses; switchgrass (Panicum virgatum L.), big bluestem (Andropogon gerardii Vitman), and giant miscanthus (Miscanthus x giganteus). Entire corn and sorghum plants were harvested after physiological maturity. Grain and stover were separated to determine respective dry weights. In addition, harvested sweet sorghum stalks were pressed to obtain a juice yield. Annual grasses were harvested after dormancy. Total dry matter yields were greatest for photoperiod sensitive (26.8 Mg ha^-1) and sweet sorghum (28.2 Mg ha^-1) varieties at both locations. Remaining sorghum variety dry matter yields ranged from 11.6 to 22.4 Mg ha^-1. Average corn dry matter yield for both locations was 21.2 Mg ha^-1. Sweet sorghum juice yields ranged from 29.4 to 33.0 Ml ha^-1. Establishment year annual grass yields ranged from 5.0 to 9.5 Mg ha^-1. Dry matter yields were generally higher for all crops at the Troy, KS location. The 2007 data indicate the highest biomass yields for renewable fuel production can be achieved by the production of sweet sorghum and photoperiod sensitive sorghum varieties, compared to other annual and perennial crops considered in this study.