Cereal-Legume Rotation Benefits Soil Ecosystem Multifunctionality by Improving the Efficiency of Microbial Carbon Pump

Abstract

Cereal-legume rotation is regarded as an important agricultural management strategy for enhancing soil organic carbon (SOC) and improving soil ecosystem multifunctionality (EMF). The soil microbial carbon pump (MCP) exerts a regulatory effect on the production of microbial necromass as well as the SOC accumulation. However, the understanding of how cereal-legume rotation regulates the link between the soil MCP and EMF remains largely insufficient. Based on this, this study was conducted by virtue of a 13-year long-term field positioning experiment in the North China Plain of China. Taking wheat-soybean (WS), wheat-maize (WM), and wheat-cotton (WC) rotation patterns as the experimental treatments, we conducted a systematic investigation and comparison of how these three rotation regimes impact soil enzyme activities, MCP efficiency, and EMF. Results demonstrated that, relative to WM and WC, WS significantly increased SOC by 11.4%–19.4%, total nitrogen by 16.7%–19.0%, dissolved organic carbon by 15.4%–27.1%, NO₃ ⁻–N by 28.5%–59.3%, and available phosphorus by 24.0%–35.6%. It also elevated microbial biomass carbon by 17.2%–18.4%, and microbial biomass nitrogen by 32.4%–36.5%. WS notably enhanced bacterial and fungal abundances by 21.8%–44.8% and 11.7%–21.7%, respectively, and stimulated the activities of β-glucosidase by 17.2%–17.4% and alkaline phosphatase by 46.9%–70.6%, accompanied by intensified soil phosphorus limitation. Moreover, WS significantly promoted microbial necromass carbon accumulation by 19.9%–29.5%, and boosted MCP efficiency by 7.7%–8.5% along with the microbial necromass accumulation coefficient by 5.2%–7.4%. While a significant discrepancy was observed in soil microbial necromass content between WM and WC, no significant differences were observed in their MCP efficiency and microbial necromass accumulation coefficient. Among these three rotation patterns, soil EMF was significantly higher in WS than in WM and WC, with WM showing a higher level than WC. The results of multi-method combined analysis showed that the cereal-legume rotation pattern regulated soil nutrient availability, altered soil microbial community structure and extracellular enzyme activities, further affected soil MCP efficiency, and ultimately drove changes in soil EMF. This study deepens the understanding of the interactive mechanism linking soil microbial carbon sequestration processes and EMF, and laying a theoretical foundation for the rational allocation and optimized utilization of rotation patterns.