Corn Stover Removal Impacts On Soil Greenhouse Gas Emissions in Irrigated Continuous Corn Systems.

Harvesting corn stover for livestock feed or for cellulosic biofuel production may impact the greenhouse gas (GHG) mitigation potential of high-yield irrigated corn.  Soil emissions of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) were measured over the 2011 growing season at two irrigated continuous corn studies in eastern and south central Nebraska.  At the eastern site, four replicates of no stover removal vs. maximum stover removal were evaluated under no-tillage and disk tillage practices.  At the no-tillage south central site, four replicates of no stover removal vs. maximum stover removal were evaluated under two irrigation levels (100%, 60%) with or without a winter rye cover crop.  All field measurements were taken on a bi-weekly basis from April (before planting) to November (after grain harvest).  Greenhouse gases were measured using vented, non-steady-state, closed chambers as per the USDA-ARS’s GRACEnet (Greenhouse gas Reduction through Agricultural Carbon Enhancement network) protocol.  Soils at both sites were CH₄ sinks over the growing season.  Total CO₂ emissions under no-tillage management were 14%-29% lower when corn stover was removed compared to when retained at both sites.  Increased CO₂ emissions from disk tillage, however, negated the reduction in CO₂ emissions from stover removal at the eastern NE site.  Total N₂O emissions at both sites were also lower when corn stover was removed compared to retained (10%-21% less at the eastern NE site, 36%-74% less at the south central NE site).  Using a winter rye cover crop to ameliorate organic matter losses due to stover removal did not affect soil CO₂ emissions, but did decrease total soil N₂O emissions by 23% compared to no amelioration practice at the south central NE site.  Implementing no-tillage and cover crops in irrigated continuous corn may enhance GHG mitigation and sustainability of forage/feedstock production in this high intensity system.