• Cover crops enhance soil carbon content, particularly in the surface soil. • Deep soil organic carbon stock improvements are more pronounced under 10-year-old than 5-year-old cover crop practice. • No-till cover crop practice has the potential to increase soil organic carbon storage along with continuous biomass inputs over long periods. • Deep soil analysis is essential to accurately assess the long-term impacts of cover crops on soil carbon storage. Anthropogenic activities have disrupted the natural carbon (C) balance, contributing to global climate change. Cover crops facilitate C sequestration, but their long-term effects 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. Soil was 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. Overall, the 10-year-old field showed greater values for all 3 parameters than the 5-year-old CC field. 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 sub-soils, providing valuable contribution to climate change mitigation.
Rambadagalla et al. (Sun,) studied this question.