Impacts of Cover Crops on Carbon Dioxide and Nitrous Oxide Flux from a Row Crop Agricultural Field in Central Illinois

Author

Joshua Dwayne Smith, Southern Illinois University CarbondaleFollow

Date of Award

5-1-2014

Degree Name

Master of Science

Department

Forestry

First Advisor

Williard, Karl

Abstract

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.