Greenhouse Gas Emission from Contrasting Management Scenarios in the Northern Corn Belt

The agricultural sector is a small but significant contributor to the overall anthropogenic greenhouse gas (GHG) emission and a major contributor of N(2)O emission in the United States. Land management practices or systems that reduce GHG emission would aid in slowing climate change. We measured the emission of CO(2), CH(4), and N(2)O from three management scenarios: business as usual (BAU), maximum C sequestration (MAXC), and optimum greenhouse gas benefits (OGGB). The BAU scenario was chisel or moldboard plowed, fertilized, in a 2-yr rotation (corn [Zea mays L.]-soybean [Glycine max (L.) Merr]). The MAXC and OGGB scenarios were strip tilled in a 4-yr rotation (corn-soybean-wheat [Triticum aestivum L.]/alfalfa [Medicago sativa L.]-alfalfa). The MAXC received fertilizer inputs but the OGGB scenario was not fertilized. Nitrous oxide, CO(2), and CH(4) emissions were collected using vented static chambers. Carbon dioxide flux increased briefly following tillage, but the impact of tillage was negligible when CO(2) flux was integrated across an entire year. The sod tended to be neutral to a slight CH(4) sink under these managements scenarios. The N(2)O flux during spring thaw accounted for up to 65% of its annual emission, compared with 6% or less due to application of N fertilizer. Annual cumulative emissions of CO(2), CH(4), and N(2)O did not vary significantly among these three management scenarios. Reducing tillage and increasing the length of the crop rotation did not appreciably change GHG emissions, Strategies that reduce N(2)O flux during spring thaw could reduce annual N(2)O emission.