Long-term effects of cover crops on soil carbon forms and stocks in no-till corn-soybean rotations in midwest USA

Authors: RAMBADGALLA, THARINDU - University Of Missouri; DAVIS, MORGAN - University Of Missouri; SINGH, GURBIR - University Of Missouri; REINBOTT, TIMOTHY - University Of Missouri; GURMESSA, BIYENSA - University Of California; UDAWATTA, RANJITH - University Of Missouri

Submitted to: Soil Security
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2026
Publication Date: 2/20/2026
Citation: Rambadgalla, T.R., Davis, M.P., Singh, G., Reinbott, T., Gurmessa, B., Udawatta, R.P. 2026. Long-term effects of cover crops on soil carbon forms and stocks in no-till corn-soybean rotations in midwest USA. Soil Security. https://doi.org/10.1016/j.soisec.2026.100230.
DOI: https://doi.org/10.1016/j.soisec.2026.100230

Interpretive Summary: Globally, soil has been losing carbon (C) at an alarming rate over the past 200 years. A machine learning based model estimated global C debt due to agriculture is 133 Pg C for the top 200 cm of soil depth (Sanderman et al., 2017). Farming practices in the United States have released 4 ± 1 × 109 Mg of C from soils, and 78±12 × 109 Mg of C globally (Fronning et al., 2008). According to the 2009 Harmonized World Soil Database (HWSD v.1.2), soils in the upper 100 cm depth contained 1325 Pg of soil organic carbon (SOC) globally (K¨ochy et al., 2015). Studies in recent years estimate that 11.3 Pg of C was emitted due to anthropogenic activities, and only 4.1 Pg C (only 36.3%) was by land-based C sinks (Lal, 2021). Increased greenhouse gas emissions are considered a main contributor to climate change. Over the past three years, record-breaking daily atmospheric and ocean have been recorded for consecutive days in the month of July (U. S. EPA, 2024). Some other parts of the world experienced record-breaking rain fall amounts and intensities (Coumou and Rahmstorf, 2012; Kundzewicz et al., 2014). The increase in frequency of unusual weather patterns affects the daily life of all living beings as well as the global economies (Parry et al., 2004).

Technical Abstract: Anthropogenic activities have disrupted the natural carbon (C) balance, contributing to global climate change. Cover crops facilitate C sequestration, but their long-term impacts and deep soil C storage in Missouri remain unexplored. This study examined soil C forms to 100 cm depth under cover crop management in corn [Zea mays (L.)] - soybean [Glycine max (L.) Merr.] rotations. Soil from 5- and 10-year-old cover crop fields in Missouri were sampled to 100 cm depth under no-till cover crop (CC) and no-till no-cover crop (NCC) treatments, and analyzed for soil organic carbon (SOC), potentially mineralizable carbon (PMC), and permanganate oxidizable carbon (POXC). Cover crops increased SOC% and stocks in both fields, with the greatest concentration at 0–5 cm depth. Cumulative SOC stocks for 0–60 cm depth under CC were 10.3% greater in 10-year-old field and 1.63% greater in 5-year-old field than NCC. Interestingly, the 10-year-old field showed strong indicatations of stable C formation. Significantly greater POXC values under CC were observed at 0–5 cm and 45–60 cm depth than NCC in 5-year old site. Additionally, PMC values were numerically greater under CC at 0–5 cm depth than NCC in both sites. Increased labile C (POXC and PMC) near the surface, suggests enhanced microbial activity and C mineralization. Greater parameter changes were notable in shallow depth (0–45 cm) but less pronounced at deeper depths (45–100 cm). These findings highlighted that long-term cover crop adoption can meaningfully enhance soil C storage in Missouri, including in sub-soils, providing valuable information for C accounting and the system's contribution to climate change mitigation.