Date of Award
Master of Science
In the United States, there is renewed interest in incorporating cover crops into agricultural systems to provide a variety of potential benefits related to soil quality, water quality, and greenhouse gas emissions. This study focused on assessing whether cover crops influence N2O and CO2 emissions in a central Illinois agricultural research field over two years (2011-2013) of cover crop growing seasons. Three winter cover crop systems, annual ryegrass (Lolium multiflorum), cereal rye (Secale cereale), and a cereal rye (2011)/ hairy vetch (Vicia villosa) (2012) rotation were planted after fall 2011 and 2012 harvests. The field included a total of eight main plots, two of each treatment, and two no cover crop control plots. Soil carbon dioxide (CO2) and nitrous oxide (N2O) fluxes were measured from the plots in a single corn (Zea mays) - soybean (Glycine max) system for two cover crop growing seasons. Fluxes of CO2 and CO2 were measured in March 2012, August 2012, and February 2013. The CO2 flux measurements were performed by using an infrared gas analyzer. The N2O fluxes were analyzed from samples collected at 0, 10, 20, 30 min intervals from the same closed dynamic chamber system. Both CO2 and N2O fluxes were computed from respective gas concentrations over time. Data were analyzed with a repeated measures mixed model procedure. N2O fluxes from the cereal rye/hairy vetch plots were greater than the no cover control and annual ryegrass plots, suggesting that cover crops may not decrease N2O fluxes immediately after being incorporated into a cropping system. In contrast, CO2 fluxes did not significantly differ among the treatments, but the cereal rye/hairy vetch plot sequestered ~100 kg C ha-1 of soil organic carbon (SOC). Overall, it was observed that some cover crop plots can have higher N2O fluxes than plots without cover crops, but cover crops have the long-term potential to sequester C in croplands demonstrating that their use should still be considered a sustainable agriculture practice.
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