Dynamics of soil organic carbon and CO2 flux under cover crop and no-till management in soybean cropping systems of the Mid-South

Authors: FIRTH, ALEXANDRA - Mississippi State University; Brooks, John; Locke, Martin; MORIN, DANA - Mississippi State University; BROWN, ASHLEY - Mississippi State University; BAKER, BETH - Mississippi State University

Submitted to: Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2022
Publication Date: 8/27/2022
Citation: Firth, A.G., Brooks, J.P., Locke, M.A., Morin, D.J., Brown, A., Baker, B.H. 2022. Dynamics of soil organic carbon and CO2 flux under cover crop and no-till management in soybean cropping systems of the Mid-South. Environments. 9(109). https://doi.org/10.3390/environments9090109.
DOI: https://doi.org/10.3390/environments9090109

Interpretive Summary: Natural landscapes lose soil organic matter, more specifically soil organic carbon. These loses normally amount to tons of carbon dioxide loss to the air which contribute to rising global temperatures. However, soil has the ability to hold and store soil carbon if properly managed. One approach to proper management is the use cover crops. In this study we investigated the use of cover crop and no tillage versus typical management, which consists of no cover crop and soil tillage. These practices were compared through the amount of soil organic carbon stored and carbon dioxide losses. Results showed that greater organic carbon was stored in no till systems, as well as greater in cover crop systems. Within these systems, the amount of bacteria present in the system could accurately predict increased carbon storage. Carbon dioxide losses were not different between the systems, however, there were differences when analyzed at the monthly time scale. This suggests that carbon loss and storage can be managed within Mid-south climates, particularly utilizing these management practices.

Technical Abstract: The transition of natural landscapes to agricultural uses has resulted in severe loss of soil organic carbon (SOC), significantly contributing to CO2 emissions and rising global temperatures. However, soil has the largest store of terrestrial carbon (C), a considerable sink and effective strategy for climate change mitigation if managed properly. Cover crops (CC) and no-till (NT) management are two management strategies that are known to increase SOC; however, adoption of these practices has been low in the mid-South due to lack of region-specific research and resistance to unproven practices. Therefore, the purpose of this study was to evaluate the impacts of CC-NT treatments in soybean cropping systems on soil %OC and CO2 flux following long-term implementation. Results showed significantly greater %OC in NT (1.27% ±0.03) than reduced tillage (RT) (1.10% ±0.03; p<0.001) and greater in both CC (rye: 1.23% ±0.03, rye+clover:1.22% ±0.03) than no cover (1.11% ±0.03; p<0.001). Bacteria abundance (p=0.005) and pH (p=0.006) were significant predictors of %OC. There was no overall significant difference in CO2 flux between tillage or CC treatments, however, there were significant differences between NT and RT in July of 2020 when %RH increased (p<0.001). Bacterial abundance negatively impacted CO2 flux (p<0.05), which contradicts most studies. The rate of proportional change and pattern of variability in C pools suggested loss of SOC in RT treatments that were not apparent when considering SOC alone. The results of this study provide valuable insight into C turnover and the effectiveness of CC use in the Mid-South to increase soil C stocks.