Submitted to: Biology and Fertility of Soils
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/15/2012
Publication Date: 5/1/2013
Citation: Cotton, J.E., Moore-Kucera, J., Acosta Martinez, V., Burow, G.B. 2013. Early changes due to sorghum biofuel cropping systems in soil microbial communities and metabolic functioning. Biology and Fertility of Soils. 49(4):403-413. Interpretive Summary: To meet the growing demands for food, fiber, and biofuels, land management decisions will require identification of most suitable crop for sustainable productivity in different geographic areas. Biofuel is known as the fuel produced from renewable resources such as biomass and forage crops to supplement fuel demand. Our study evaluated the use of sorghum for biofuel initiatives in soils with low organic matter (marginal lands) due to intensive agricultural production under low biomass cotton cropping. We believe that if managed under high biomass cropping systems, these marginal lands may experience an improvement in their soil quality and functioning. In our study, we detected changes in soil microbial communities and their enzyme activities important for nutrient cycling and organic matter during the two year transition from long-term cotton cropping systems to sorghum biofuel cropping systems. This study has evaluated agronomic and cropping systems technology that can be applied towards sustainable sorghum production for integrated bioenergy/forage application with emphasis on minimizing water demand and improving soil quality. Early results from this study suggest improvements in soil quality and the sustainability of sorghum biofuel cropping for low organic matter agricultural soils.
Technical Abstract: Evaluation of biofuel production cropping systems needs to address not only energy yields but also the impacts on soil attributes important for long-term sustainability. In this study, forage sorghum (Sorghum bicolor L. Moench) cropping systems were initiated on a low organic matter soil (<0.9%) with a history of intensively-tilled low-input cotton production in the semiarid Southern High Plains of the U.S. Sorghum cropping systems were evaluated in a split-plot design with sorghum cultivar as the main plot and the combination of irrigation level (non-irrigated and deficit irrigated) and aboveground biomass removal rate (50% and 100%) as the split plot. The sorghum cultivars used varied in yield potential and lignin content, which are important features for feedstock-producing crops. Changes in soil microbial properties (0-10 cm) were detected during the two year transition from long-term cotton cropping systems to sorghum biofuel cropping systems. Increases in microbial biomass C (16%) and N (17%) and differences in fatty acid methyl ester (FAME) profiles were detected after one growing season. Enzyme activities targeting C, N, P, and S cycles increased 15-75% after two growing seasons. Additionally, increases in enzyme activities (16-19%) and differences in FAME profiles were seen due to irrigation regardless of aboveground biomass removal rate, which may be due to an increase in belowground biomass production even with limited irrigation. Biomass removal rate and the cultivar type had little effect on the soil microbial properties during the time frame of this study. Early results from this study suggest improvements in soil quality and the sustainability of sorghum biofuel cropping for low organic matter agricultural soils.