Greenhouse Gas Emissions and Microbial Dynamics in Bioenergy Crops on Retired Marginal Agricultural Fields in the Lower Mississippi Alluvial Valley.

The Lower Mississippi Alluvial Valley (LMAV) has favorable climate, port access, and infrastructure for producing biofuels.  Two crops being explored for agricultural fields retired from row crop production due to marginally productive soils are switchgrass (Panicum virgatum L.) and eastern cottonwood (Populus deltiodes L).  In 2009 both crops were planted in retired agricultural fields at two sites in the LMAV.  At each site, a soybean-sorghum rotation was planted as well to provide a comparison of cottonwood and switchgrass with crops that are typically grown on such sites.  As a component of this study, methane, nitrous oxide, and carbon dioxide emission rates are being assessed for inclusion in a carbon life cycle analysis of producing each crop.  These emissions have been sampled monthly since February 2013 and analyzed using gas chromatography.  Microbial biomass carbon, labile soil carbon, and microbial dehydrogenase activity  in soil has also been assessed quarterly in tandem with gas sampling  Responses of these gas and soil parameters will be presented.