Greenhouse gas emissions from soils in corn-based cropping systems

Crop rotation is a management practice with high greenhouse gas (GHG) mitigating potential that is often neglected due to economic influences. Three long-term rotation studies in Wisconsin were selected to assess the potential opportunities for mitigating GHG emissions by comparing the temporal and spatial variability of N2O, CO2, and CH4 emissions in continuous corn (CC) (Zea mays L.), corn-soybean (CS) [Glycine max (L.) Merr.], and corn-soybean-wheat (CSW) (Triticum aestivum L.) using a static chamber method. GHG emissions were influenced by weather conditions and following nitrogen (N) application during a 3-year measurement period. In high N input environments at Arlington and Lancaster, N2O emissions in CC were 5.80 and 4.40 kg N ha-1, respectively, which was much higher than the emissions in CS and CSW rotations that ranged from 1.52 to 3.33 kg N ha-1. In the low N input environment at Marshfield, N2O emissions were not statistically different among CC, CS, and CSW rotations (1.20-1.66 kg N ha-1). Yield-scaled N2O emissions were not different among crop rotations. When pooled over locations, CO2 emissions were highest in CC (4.16 Mg C ha-1) and were similar in CS and CSW (3.71 and 3.50 Mg C ha-1, respectively). Soils either emitted or absorbed small and inconsistent amounts of CH4. These results provide important insights as to how weather conditions and differences among management practices affect GHG emissions and show that application of either 2-year CS or 3-year CSW rotation can be equally effective in reducing N2O emissions compared to CC, especially with high N applications. N2O emission peaks were recorded when high rainfall events occurred shortly after N fertilizer was applied.Two-year CS or 3-year CSW rotation can be equally effective in reducing N2O emissions compared to CC.Differences in yield-scaled N2O emissions were not observed among rotations or across environments.Generally, soils acted as a minor CH4 sink.