Soil Nitrous Oxide Emissions in Corn following Three Decades of Tillage and Rotation Treatments

Few experiments have directly compared the long-term effects of moldboard, chisel, and no-till tillage practices on N2O emissions from the predominant crop rotation systems in the midwestern United States. This study was conducted from 2004 to 2006 on a tillage and rotation experiment initiated in 1975 on a Chalmers silty clay loam (a Typic Endoaquoll) in west-central Indiana. Our objectives were to assess (i) long-term tillage (chisel [CP], moldboard plow [MP], and no-till [NT]), rotation (continuous corn [Zea mays L.] and corn-soybean [Glycine max (L.) Merr.]), and rotation x tillage interaction effects on soil N2O emission, and (ii) how soil N2O emission is related to environmental factors during corn production under identical N fertilizer management. Seasonal N2O emissions were measured at intervals ranging from a few days to biweekly for up to 14 sampling dates in each growing season for corn. Nitrous oxide emissions during the growing season were significantly affected by tillage and rotation but not their interaction; however, 50% of total emissions occurred shortly aft er N application regardless of tillage or rotation practices. Seasonal cumulative emissions were significantly lower under NT but not statistically different for CP and MP. Overall, emissions under NT were about 40% lower relative to MP and 57% lower relative to CP. Rotation corn lowered N2O emissions by 20% relative to continuous corn. Higher N2O emission under MP and CP appeared to be driven by soil organic C decomposition associated with higher levels of soil-residue mixing and higher soil temperatures.