The Impact of Corn Stover Removal on Soil Microbial Communities in No-till and Conventional till Continuous Corn.

Corn (Zea mays L.) residue, or stover, can be used as a dry forage replacement in beef cattle diets and is being considered as a feedstock for cellulosic biofuel production. The soil quality and crop productivity ramifications of removing stover, however, likely will depend on stover removal rate and other management practices (i.e. tillage). Our objectives were to evaluate the impacts of stover removal rate and tillage on soil microbial communities by profiling microbial fatty acid methyl esters (FAMEs) in a 10-yr, irrigated, continuous corn study in the western Corn Belt (Ithaca, NE).  Microbial FAMEs were used to estimate soil microbial biomass and evaluate soil fungal:bacterial (F:B) ratios throughout the 2014 and 2015 growing season under conventional disk tillage (CT) and no-till (NT) with variable stover removal rates (none, moderate, and high). In both years, removing residue decreased total microbial biomass with no change in the F:B ratio indicating general substrate limitation over selective loss of niche. Tillage, but not residue removal, led to slight declines in arbuscular mycorrhizal fungal (AMF) biomass. The F:B ratio was also sensitive to tillage, being greater in plots that were disked across all residue removal treatments. Understanding how the removal of corn stover affects soil microbial communities, and in turn, soil quality, can aid in the development of corn stover removal thresholds which maintain or improve soil quality while providing a necessary feedstock for bioethanol production.