Title: Greenhouse gas fluxes from no-till rotated corn in the Upper Midwest Authors
Submitted to: Agriculture, Ecosystems and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 1, 2013
Publication Date: April 15, 2013
Citation: Lehman, R.M., Osborne, S.L. 2013. Greenhouse gas fluxes from no-till rotated corn in the Upper Midwest. Agriculture, Ecosystems and Environment. 170:1-9. Interpretive Summary: Agriculture is an important producer and consumer of atmospheric gases (carbon dioxide, nitrous oxide, methane) that moderate global climate. Agricultural practices such as tillage, fertilization, and irrigation are major factors for the production of these gases. Ground based-data on greenhouse gas (carbon dioxide, nitrous oxide, methane) fluxes from regionally-dominant agricultural practices are needed to validate predictive modeling of global climate effects (positive or negative) associated with agriculture. We determined soil surface gas fluxes from no-till, dryland corn in eastern South Dakota. Corn is the dominant crop with high fertilizer requirements. We compared gas fluxes from corn grown in a 2-year (corn-soybean) rotation with that grown in a 4-year (corn-field peas-winter wheat-soybean). Our CO2 and N2O fluxes were lower than those measured by other researchers in neighboring states, probably due to a combination of environmental (temperature, moisture) and agronomic (tillage, fertilization) factors. In contrast, we found positive methane fluxes which differs from neutral or negative fluxes observed by other researchers. This finding is likely due to an extended period of high precipitation and snow cover coincident with study period. We found no difference in greenhouse gas fluxes from corn due to rotation; however, there was an increase in soil carbon in the 4-year rotation compared to a decrease observed in the 2-year rotation. Since the 4-year rotation is sequestering soil carbon, it is likely to be a net consumer of greenhouse warming potential, while the 2-year rotation is likely to be a net producer of greenhouse warming potential. This research documents benefits of diversified crop rotations with respect to global carbon budgets and the potential of global climate change. These data enable predictive modeling of future global climates and contribute to the development of best management practices for regional agriculture.
Technical Abstract: We determined soil surface fluxes of greenhouse gases (carbon dioxide, nitrous oxide, methane) from no-till, dryland corn (Zea mays L.) in eastern South Dakota and tested the effect of rotation on greenhouse gas fluxes from corn. The corn was grown within a randomized, complete block study that included both a 2-year (corn-soybean) rotation and a 4-year (corn-field peas-winter wheat-soybean) rotation with plots containing the corn phase present in every year, 2007 - 2010. Annual carbon dioxide (CO2) fluxes were between 1500 and 4000 kg CO2-C ha-1 during the four-year study. Annual nitrous oxide (N2O) fluxes ranged from 0.8 to 1.5 kg N2O-N ha-1 with peak fluxes during spring thaw and following fertilization. Net methane (CH4) fluxes in 2007 were close to zero, while fluxes for 2008 – 2010 were between 0.9 and 1.6 kg CH4-C ha-1. Methane fluxes increased with consistently escalating values of soil moisture over the four-year period demonstrating that soils which previously exhibited neutral or negative CH4 flux may become net CH4 producers in response to multiyear climatic trends. No significant differences in gas fluxes from corn due to treatment (2-year vs. 4-year rotation) were observed. Mean net annual soil surface gas fluxes from corn calculated over four years for both treatments were 2.4 Mg CO2-C ha-1, 1.2 kg N2O-N ha-1, and 0.9 kg CH4-C ha-1. Annual global warming potentials (GWP) as CO2 equivalents were 572 kg ha-1 and 30 kg ha-1 for N2O and CH4, respectively. Measurements of soil carbon showed that the 4-yr rotation accrued 771 kg C ha-1 yr-1 in the top 30 cm of soil which would be more than sufficient (2.8 Mg CO2 eq ha-1 yr-1) to offset the annual GWP of the nitrous and methane emissions from corn. In contrast, the 2-year rotation lost 83 kg C ha-1 yr-1 from the top 30 cm of soil resulting in corn being a net producer of greenhouse gases and associated GWP. [GRACEnet publication]