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 N₂ O, 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, N₂ O 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, N₂ O emissions were not statistically different among CC, CS, and CSW rotations (1.20-1.66 kg N ha^-1 ). Yield-scaled N₂ O 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 N₂ O emissions compared to CC, especially with high N applications.