Greenhouse Gas Emissions from a No-till, Corn-Soybean Rotation with Removal of Corn Residue.

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, including emissions of greenhouse gases.  We measured four years of soil surface fluxes of greenhouse gases (CO₂, N₂O, and CH₄) using the static chamber technique in replicated research plots (24 m x 30 m plots; no-till, corn-soybean rotation) established in 2000 in Brookings, SD.  One treatment was the removal of the corn residue plus grain and the other treatment (control) was the removal of corn grain only.  Slightly higher CO₂ fluxes were measured in the plots with grain only removal compared to grain plus residue removal, presumably from decomposition of the additional residue.  Annual CO₂ fluxes ranged from 1 – 2 Mg CO₂-C/ha.  There was little treatment effect on annual N₂O fluxes, although summer fluxes following N fertilization tended to be highest without stover removal.  In contrast, the following early spring N₂O fluxes tended to be highest with stover removal, possibly because poorer soil structure with residue removal promoted saturated conditions.  Annual N₂O fluxes ranged from 0.5 – 5 kg N₂O-N/ha.  There was no effect of residue treatment on annual CH₄ fluxes which ranged from 0.5 – 1.5 kg CH₄-C/ha.  Related research on these plots has shown decreased soil carbon in the plots with residue removal, so with the small difference in the greenhouse gas production, residue removal results in a net production of global warming potential.