Role of cover crop roots in soil organic carbon accrual—A review

Appropriate cover crop (CC) management is an important tool for the improvement of soil carbon stock; however, the relationships between carbon accumulation and CC root traits remain unclear. A literature review was performed to identify the extent and focus of recent research and to answer questions about the role of root traits of CCs in soil C accumulation with regard to species selection, mixture composition and agronomic management. The findings based on the analysis of 69 publications show that a range of root traits such as root biomass, architecture, depth of rooting, root chemical composition, as well as quantity and quality of rhizodeposition, can contribute to soil structure formation and C accumulation. These traits are usually species specific, and it seems that appropriate species combinations in the mixtures can offer the highest potential for optimization of C stock across various environments. However, there has been twice as much recent research on roots of CC monocultures than on mixtures, with little attention paid to agronomic aspects such as plant spatial arrangement or soil tillage in relation to CC root development. Considerations of real management under field conditions could be beneficial in providing greater accuracy of estimation of the contribution of CCs in increasing the SOC stock in croplands.