Straw Decomposition Characteristics, Determinants, and Ecological Effects in the Four Major Grain-Producing Regions of China

Straw return is an important practice for replenishing soil organic matter (SOM) and recycling agricultural residues. This review synthesizes straw decomposition characteristics, drivers, and agroecological effects across China’s four major grain-producing regions. The relevant literature was retrieved from the Web of Science Core Collection, Scopus, and China National Knowledge Infrastructure (CNKI) and manually selected based on their relevance to straw decomposition and associated agroecological responses. In Northeast China, low temperature and a short effective decomposition period limit straw breakdown. In the Huang-Huai-Hai region, intensive winter wheat–summer maize rotation, seasonal straw inputs, and fluvo-aquic soil properties regulate decomposition. In the middle and lower reaches of the Yangtze River, favorable hydrothermal conditions support decomposition, while paddy–upland alternation and flooding modify decomposition pathways. In Southwest China, warm, humid conditions favor decomposition, but erosion and nutrient losses on sloping croplands can weaken long-term fertility benefits. Straw return can improve SOM accumulation, nutrient availability, soil structure, and crop productivity; however, these benefits depend on climate, soil properties, cropping systems, and management. Responses of CO2, CH4, and N2O emissions also vary, particularly with soil moisture and nitrogen management. Future studies should integrate long-term field experiments, microbial ecology, carbon–nitrogen cycling, and life cycle assessment to develop region-specific straw return strategies that balance agronomic benefits and environmental risks.