ARS | Publication request: Dynamics of soil microbial communities in agroecosystems managed for biofuel production

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 2, 2010
Publication Date: October 22, 2010
Citation: Lehman, R.M., Osborne, S.L. 2010. Dynamics of soil microbial communities in agroecosystems managed for biofuel production. International Symposium on Microbial Ecology, Seattle WA.

Technical Abstract: Elevated atmospheric CO2 concentrations and their link to global climate change are stimulating efforts to reduce dependence on fossil fuels and increase use of alternative energy sources. Initial efforts to incorporate significant amounts of cellulosic ethanol into transportation fuels are focused on utilizing crop residues, primarily corn, from lands under intensive agricultural production management. The removal of crop residues may result in negative impacts to the function and sustainability of these agroecosystems. We are studying the effect of crop residue removal on soil properties, including the dynamics of soil microbial communities using quantitative PCR of rRNA genes from major taxonomic groups and the fluxes of greenhouse gases (CO2, N2O, and CH4). Replicated research plots (24 m x 30 m plots; corn-soybean rotation) were established in 2000 where one primary treatment (biofuel management) is the removal of the corn residue plus grain and the other primary treatment (control) is the removal of corn grain only. In 2005, plots were split to add cover crops as a secondary treatment to examine the potential for cover crops to mitigate decreases in soil carbon observed in the biofuel treatment plots. In soil samples collected following crop harvest in 2009, we have found the highest fungal:bacterial ratios (0.1) in plots with corn and lower ratios (0.05) in the plots with soybean. There were no significant effects on soil fungal:bacterial ratios due to residue removal or the addition of a cover crop apparent at this sampling time, despite changes in the quantity and quality of organic carbon due to both treatments. Ongoing analyses target the quantification of Basidiomycota, Acidobacteria, Firmicutes, Actinobacteria, and Bacteriodetes in these samples and the compilation of the gas flux data. These data will assist in determining if significant changes may occur in the functioning of agroecosystems managed for cellulosic biofuel production.