Temporal Changes in Greenhouse Gas Fluxes and Related Soil Properties Under Long-Term Tillage Systems.

Intensive tillage results in losses of soil organic matter (SOM) through soil disturbance and decomposition of SOM by microbes, leading to increased CO₂ emissions to the atmosphere. Limited research is available to evaluate the impact of tillage on CO₂ emissions and related properties from a temporal perspective. The objective of this study was to evaluate temporal impacts of six tillage systems [chisel, plow, disk, disk with rye (Secale cereale L.) cover crop (CC), no-till (NT), and no-till with rye CC], under soybean (Glycine max L.)-corn (Zea mays L.) rotation on CO₂-C fluxes and related soil properties on a silty clay loam soil after 30 yr of management. Soil samples for analysis of particulate organic matter (POM) were collected seasonally. Soil gas fluxes were collected every 1.5 to 2 h immediately following tillage, and then after one week and monthly. Late fall through summer cumulative CO₂-C fluxes were unaffected by tillage treatments. Cumulative CO₂-C fluxes calculated by season did not differ by tillage treatment but tended to be greater in summer compared to winter or spring. In winter, POM concentration was lowest in plow till of all tillage treatments. In spring, POM concentration was lower in chisel and plow treatments compared to disk or NT treatments, potentially due to soil disturbance and oxidation of SOM. Overall, the reduction in POM concentration with plow or chisel can lead to reductions in SOM concentration compared with NT although CO₂-C fluxes were generally not greater under plow or chisel treatments compared to NT.