There is insufficient experimental data to accurately assess the effects of long-term tillage and rotation systems on greenhouse gas fluxes in the Midwest Corn Belt. This research was initiated to determine short- and seasonal fluxes of CO2 and CH4 in soils that have been uniformly managed using MP, CP and NT tillage practices in CC and RC for the last 3 decades. Short-term CO2 emission measured for 168 h after fall primary tillage was higher for CP than for MP at all time of measurement. On a seasonal basis, CO2 emission during the growing season was significantly affected by rotation (CC averaged 16% higher than RC), but not by tillage systems. However, among tillage systems CO2 emission was numerically in the order: NT < MP < CP. Tillage and rotation had significant effects on methane fluxes in the short-term, but neither tillage nor rotation had significant effects on methane fluxes during the growing season. Although the soils were a net sink for CH4, fluxes were generally very low and suggested that even 30 years of continuous NT did not significantly improve CH4 uptake in these soils. Soil temperature and moisture effects on gas fluxes were significant, but specific relationships of temperature and moisture with gas emission were generally poor, and dependent on both seasonal timing of gas measurement as well as the tillage systems under consideration.Our results suggested that the effects of fall primary tillage operations on gas fluxes are relatively short-lived, and that rotation system seemed to be a more important factor determining the dynamics of seasonal gas fluxes from the soil surface. Similarly, from a short-term perspective, since adoption of a NT management system will minimize soil disturbance and increase crop residue retention on the surface, NT is more effective in reducing greenhouse gas emissions compared to MP and CP. However, in the long term, CP may be more detrimental than MP systems in net CO2 emissions while both CP and MP appeared to have an equally marginal effect on CH4 uptake or loss in these dark prairie soils.
Acknowledgements
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