Investigating the impact of cover crops on greenhouse gas emissions in the Southern Great Plains region

The agriculture sector has been estimated to be responsible for a significant portion of greenhouse gas emissions worldwide. Cover crops have been found to improve soil health by increasing soil organic matter, recycling nutrients, and reducing erosion. The objective of this project was to understand the effects of cover crops on greenhouse gas emissions, specifically in the Southern Great Plains. Nitrous oxide (N₂O) and carbon dioxide (CO₂) gas emissions were measured using steady-state gas flux chambers in a winter wheat-cotton cropping system rotation at Caddo Research Station in Ft. Cobb, Oklahoma. Winter wheat was planted as the cover crop with early termination, late termination, and no cover as main treatments. The gas samples were collected weekly in glass vials and were analyzed using a Varian-450 gas chromatograph (GC). The average gas emissions are estimated during the cover crop phase and cotton production phase. The flux of both gases was calculated using linear regression analysis and the ideal gas law, and the means of each treatment were compared for significance. Primary results of this study found no significant difference in N₂O and CO₂ emissions across the cover crop treatments during the cover crop phase and cotton production phase. However, there was a significant difference between average N₂O and CO₂ emissions in 2023 and 2024, likely attributed to temperature and moisture variability. Additionally, N₂O emissions were significantly higher in the cotton production phase than the cover crop phase in both years, indicating that nitrogen fertilizer may also play a role in N₂O emissions. In contrast, CO₂ emissions varied widely between crop phases and may depend on differences in weather, microbial activity, and decomposition rates. The results of this study highlight the variability of the efficiency of cover crops to mitigate greenhouse gas emissions, specifically in regions where weather conditions can be unpredictable, and drought is prevalent.