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

Abstract

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 soil 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.