FARMING PRACTICES FOR THE NORTHERN CORN BELT TO PROTECT SOIL RESOURCES, SUPPORT BIOFUEL PRODUCTION AND REDUCE GLOBAL WARMING POTENTIAL
Location: Soil and Water Management Research
Title: Impact of Reduced Tillage and Cover Cropping on the Greenhouse Gas Budget of a Maize/Soybean Rotation Ecosystem
Submitted to: Agriculture, Ecosystems and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 14, 2009
Publication Date: August 14, 2009
Citation: Bavin, T., Griffis, T.J., Baker, J.M., Venterea, R.T. 2009. Impact of Reduced Tillage and Cover Cropping on the Greenhouse Gas Budget of a Maize/Soybean Rotation Ecosystem. Agriculture, Ecosystems and Environment. 134(3):234-242.
Interpretive Summary: Given the potential dangers of global climate change, it is important to determine whether changes in agricultural management practices can help reduce net greenhouse gas emissions. We tested two practices that have been proposed for reducing the net emissions in corn/soybean systems: reduced tillage and winter cover cropping. Gas exchange was measured in two adjacent fields in 2004 and 2005. One field was managed as a conventional corn/soybean system with chisel/disk tillage. The other field was also in corn/soybean rotation, but with a winter rye cover crop following the corn, and with strip tillage instead of chisel plowing. Gas exchange measurements were made in both systems to determine soil respiration (CO2), CH4 (methane), and N2O (nitrous oxide). Soil respiration was higher in the alternative system, primarily due to the decomposition of the rye cover crop. N2O emissions were higher in the conventional system, while CH4 exchange was negligible in both systems. Overall, considering the relative warming potential of each gas, there was little net greenhouse gas benefit from the alternative farming system, suggesting that other strategies must be explored. These results will be useful in developing policies and practices that help agricultural producers play a positive role in mitigating potential climate change.
The objective of this study was to evaluate the impact of an alternative management scenario (reduced tillage and cover cropping) on ecosystem respiration and N2O and CH4 exchange in a maize (Zea mays L)/soybean (Glycine max L.) rotation agroecosystem in north-central Minnesota. The control treatment was managed using fall tillage with a chisel plow in combination with a tandem disk and the experimental treatment was managed using strip tillage and a winter rye (Secal cereale) cover crop. Over the two-year study period (2004 through 2005), cumulative RE was 222.7 g C m-2 higher in the alternatively managed treatment as a result of increased decomposition of the cover crop residue. N2O fluxes were similar in both treatments during the 2004 growing season and were 100.1 mg N m-2 higher in the conventional treatment during the 2005 growing season after N fertilization. N fertilization and fertilizer type were the dominant factors controlling N2O fluxes in both treatments. CH4 fluxes were negligible in both treatments and often below the detection limit. Compared to RE, the N2O and CH4 fluxes were small components of the total greenhouse gas budget. However, cumulative growing season N2O losses in the control and experimental treatments, which totaled 38.9 ± 3.1 g C m-2 and 26.1 ± 1.7 g C m-2, were comparable to the annual estimates of net ecosystem CO2 exchange in both treatments. This study further supports that N2O losses from agricultural ecosystems are an important component of the total greenhouse gas budget and that alternative management strategies, including reduced tillage and cover cropping, have limited potential of reducing greenhouse gas emissions in upper Midwest maize/soybean agroecosystems.