Green manuring increased peanut yields and reduced soil carbon mineralization by optimizing microbial communities

Abstract

Using green manure (GM) in rotations is a sustainable approach to cleaner production and soil CO2 emissions mitigation, yet the microbial mechanism governing soil organic carbon (SOC) mineralization from legume fields remains to be elucidated. To determine whether the GM-based rotation was superior to the conventional continuous peanut monoculture, a seven-year field experiment including two cropping regimes, peanut continuous monoculture (P) and peanut-Orychophragmus violaceus rotation (PO), was performed. Microbial properties and C-degradation enzyme activities in the rhizosphere and bulk soil of peanut fields were explored, with SOC mineralization (Kc) and its temperature sensitivity (Q10) determined in the laboratory. O. violaceus incorporation as a GM enhanced soil moisture, pH and mineral nitrogen contents, which increased the bulk soil bacterial alpha diversity and reduced rhizosphere fungal richness. GM incorporation promoted saprotrophs (Agaricales), enriched beneficial microbes (Bacillus) and inhibited pathogenic fungi (Fusarium), thus alleviating continuous monoculture obstacles and increasing yields. The bacterial interaction complexity was increased, but the fungal interaction complexity was reduced. Moreover, GM not only decreased the rhizosphere Q10 (by 14.9%) due to decreased rhizosphere SOC but also reduced the bulk soil Kc (by 23.9%) due to the intensified C limitation, indicating that the C loss of bulk soil is currently low and that of the rhizosphere will be limited under future warming. This study provides new insight into soil C mineralization in legumes at the microenvironmental scale, and improves our projections of legume soil C loss under future climate change scenarios.