Resource information
The agricultural sector is a small but significant contributor to the overall anthropogenic greenhouse gas (GHG) emission and a major contributor of N2O 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 CO2, CH4, and N2O 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, CO2, and CH4 emissions were collected using vented static chambers. Carbon dioxide flux increased briefly following tillage, but the impact of tillage was negligible when CO2 flux was integrated across an entire year. The soil tended to be neutral to a slight CH4 sink under these managements scenarios. The N2O 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 CO2, CH4, and N2O 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 N2O flux during spring thaw could reduce annual N2O emission.
