Rice straw returning to the field on soil microbial interactions, soil fertility improvement, and carbon sequestration for CO2 emission reduction.

Rice straw is rich in organic matter and essential nutrients, an important resource for improving soil fertility and enzyme activity. However, its high carbon-nitrogen ratio leads to slow decomposition, affecting nutrient transformation efficiency. The small molecular carbohydrates released during microbial enzymolysis not only serve as an energy source but may also act as signaling molecules, participating in the regulation of soil microbial community structure and plant root development. This review discusses the effects of straw return to the field on soil organic carbon (SOC) stability, microbial activity, and plant-soil feedback mechanisms, with particular emphasis on its role in carbon sequestration and CO2 emission mitigation. By enhancing SOC storage and aggregate stability, rice straw returning transforms agricultural waste into a long-term carbon sink, potentially offsetting a portion of anthropogenic CO2 emissions despite short-term increases in soil respiration and greenhouse gas (GHG) fluxes during decomposition. Optimized integration with water-nitrogen management and microbial inoculants can maximize net carbon benefits while sustaining soil fertility. This review highlights the key role of microbial-mediated straw decomposition in agricultural ecosystems and waste valorization. Future research needs to focus on the receptor recognition pathways of specific carbohydrate signals (fiber oligosaccharides, lignin oligosaccharides), the spatiotemporal dynamics of interspecies signaling between microorganisms and plants, the regulatory effects of environmental factors (soil pH, moisture) on signaling pathways, and quantitative modeling of long-term CO2 reduction potentials at regional and global scales.