Influence of Species Composition and Management on Biomass Production in Missouri.

Bioenergy acts and Farm Bills have promoted renewable energy production with a mandate to produce 136 billion L of biofuel by 2022. Although monocultures have been promoted for biomass production recent studies have shown that a highly diversified cropping system has the potential to produce equal if not greater biomass for biofuel production than monocultures. The objectives of this study was to examine the effects of cutting time, cutting height, and plant mixture diversity on feedstock yields. The study was established at the Bradford Research Center University of Missouri and feed stock yields were determined from 2010-2012. A 1:1 mixture of switchgrass (Panicum virgantum L.) and bluestem (Andropogon gerardii Vitman) was the main grass mixture. The main grass mixture was mixed with a mixture of native forbs and legumes seeded at 100:0 (T1), 80:20 (T2), 60:40 (T3), and 20:80 (T4) ratios were used in the study. Two cutting heights were 15 and 30 cm. The average feed stock yields were 4.96, 5.58, and 5.16 Mt y^-1 for 2010, 2011, and 2012. In 2011, yields varied between 5.42 Mt y^-1 for T2 to 5.81 Mt y^-1 for T1. During the study, T1 recorded the greatest yields but differences were not significant among mixtures. The 15-cm cutting height treatment had significantly greater yields by year and for each cutting. The 3-year averages were 6.45 and 4.06 Mt y^-1 for 15-cm and 30-cm cutting heights. The yield differences were 2.43, 2.38, and 2.36 Mt y^-1 for 2010, 2011, and 2012 between the two cutting height treatments. Results from the study in Central Missouri suggests that feedstock yields fluctuate from year to year and precipitation may have influenced the fluctuation. The mixture composition had no effect on feed stock yields. However, the lower cutting height produced significantly greater yields.