Cover cropping promotes soil carbon sequestration by enhancing microaggregate-protected and mineral-associated carbon

Authors: ZHU, SHAOQING - Northwest University; Sainju, Upendra; ZHANG, SHAOHONG - Northwest University; TAN, GUANGYE - Northwest University; WEN, MENGMENG - Northwest University; DOU, YING - Northwest University; YANG, RUIJIA - Northwest University; CHEN, JINFA - Northwest University; ZHAO, FAZHU - Northwest University; WANG, JUN - Northwest University

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/2/2023
Publication Date: 11/6/2023
Citation: Zhu, S., Sainju, U.M., Zhang, S., Tan, G., Wen, M., Dou, Y., Yang, R., Chen, J., Zhao, F., Wang, J. 2024. Cover cropping promotes soil carbon sequestration by enhancing microaggregate-protected and mineral-associated carbon. Science of the Total Environment. 908:168330. https://doi.org/10.1016/j.scitotenv.2023.168330.
DOI: https://doi.org/10.1016/j.scitotenv.2023.168330

Interpretive Summary: It is known that cover cropping promotes carbon sequestration, when compared to no cover cropping, by supplying additional cover crop residue C input, but the mechanism of carbon stabilization in soil aggregates is not well understood. An ARS scientist in Sidney, MT, in collaboration with researchers from Northwest University, Xian, China, conducted a laboratory analysis of carbon sequestration in aggregates in soil samples from a long-term cover crop experiment in the Loess Plateau of China. They reported that cover cropping increased soil aggregation and stability, when compared to no cover cropping, as well as enhancing soil carbon sequestration by increasing micro-aggregate protected and mineral-associated carbon, which are both considered protected carbon fractions against decomposition. They also found that a mixture of legume and nonlegume cover crops was more effective in increasing protected carbon fractions than individual cover crop species. Producers can enhance soil carbon sequestration and stabilization by using a mixture of legume and nonlegume cover crops.

Technical Abstract: Cover cropping can enhance soil C sequestration compared to no cover cropping, but the mechanism of C stabilization in soil aggregates needs more explanation. We explored C stabilization in soil aggregates by cover crops in a summer cover crop – winter wheat (Triticum aestivum L.) rotation system in the Loess Plateau of China. Cover crops were soybean (Glycine max L., SB), sudangrass (Sorghum sudanense (Piper) Stapf, SG), a mixture of soybean and sudangrass (SS), and no cover crop (CK). Carbon fractions were coarse particulate organic C (cPOC), intra-microaggregate fine particulate organic C (iPOC), free fine POC (fPOC), and mineral-associated organic C (MOC). The iPOC and MOC are considered as protected C against mineralization. Cover crops increased the proportion of large macroaggregates at 0-10 cm by 18-22% compared to no cover crop, with SS having greater mean-weight diameter (MWD). Cover crops had greater MOC, iPOC, and fPOC concentrations than no cover crops in most aggregate-size classes and bulk soil at all depths, with SS having the greatest concentration. Cover crops also increased the storage of MOC, iPOC, and cPOC in aggregates and bulk soil compared with no cover crop, with more storage for SS than SB and SG. More C was stored in MOC than any other fractions. Cover crops can enhance soil aggregation and C sequestration compared to no cover crop by increasing protected C and a cover crop mixture was more effective in promoting soil aggregate stability and protected C than single species.