The Innovation Team of Fertilizer and Fertilization Technology at the Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS) has discovered that the joint utilization of green manure and rice straw can expand the soil carbon pool through the stoichiometric regulation of extracellular enzymes. The related findings were published under the title "Rice straw returning under winter green manuring enhances soil carbon pool via stoichiometric regulation of extracellular enzymes" in the international Soil & Tillage Research journal.

The combined utilization of vetch and rice straw is a win-win measure in rice production that balances rice yield stability and enhances soil carbon sequestration potential. However, the quantification of soil carbon sequestration effects under this measure and its underlying mechanisms are not yet clear. Environmental and biological factors influence the straw decomposition process, determining the fate of plant-derived and microbial carbon, thereby affecting the accumulation and stability of soil organic carbon. Improvements in the quality (carbon-nitrogen ratio) of the mixture directly impact the production of microbial communities and their extracellular enzymes, serving as potential driving factors for soil carbon pool formation. Therefore, linking substrate decomposition, extracellular enzyme stoichiometry, and soil carbon pool contributes to elucidating the organic carbon turnover processes between plants, microbes, and soil, thereby clarifying the pathway mechanism of straw-derived carbon conversion to soil carbon.

This study, based on field positioning experiments in Changsha, Hunan Province, conducted a two-year decomposition experiment from April 2021 to April 2023. Experimental treatments included: fallow (CF), vetch sole utilization (GM), rice straw sole utilization (S), and vetch and rice straw combined utilization (GMS), with the vetch and rice straw under combined utilization labeled as C-GM and C-S, respectively. By studying soil carbon pool composition, vetch and rice straw decomposition and nutrient release patterns, and the dynamic changes in extracellular enzyme stoichiometry, the study elucidated the pathway mechanism of soil carbon pool formation under vetch and rice straw combined utilization.

The joint utilization of vetch and rice straw regulates extracellular enzyme production by improving the nutrient stoichiometry of the mixture. Under combined utilization, microbial metabolism carbon is relatively limited, while phosphorus limitation is weakened, thereby promoting residue decomposition. The carbon released from the vetch and rice straw mixture not only increases the content of soil labile organic carbon but also promotes the accumulation of amino sugars in the soil carbon pool, thereby enhancing soil organic carbon reserves. This study emphasizes that incorporating green manure into rice planting systems is an effective measure to promote the utilization of rice straw resources and enhance soil carbon sequestration capacity.

Li Shun, a doctoral student at the College of Resources and Environmental Sciences, Nanjing Agricultural University, is the first author of this paper, with Researcher Cao Weidong from the Institute of Agricultural Resources and Regional Planning of the Chinese Academy of Agricultural Sciences and Associate Professor Gao Songjuan from Nanjing Agricultural University as corresponding authors.

The research was supported by the Key Laboratory of Efficient Utilization of Northern Arid and Semi-arid Cropland, the National Key Research and Development Program during the 14th Five-Year Plan (2021YFD1700200), the National Green Manure Industry Technology System (CARS-22), and the National Natural Science Foundation of China (32202609, 32072678).

Citation: Shun Li, Guodong Zhou, Guopeng Zhou, Jun Nie, Jianglin Zhang, Songjuan Gao, Weidong Cao. Rice straw returning under winter green manuring enhances soil carbon pool via stoichiometric regulation of extracellular enzymes. Soil & Tillage Research, 2025, 252, 106617.

Original Link: https://doi.org/10.1016/j.still.2025.106617