Biochar accelerates straw decomposition and reduces greenhouse gas emissions by driving microbial community dynamics

The rational utilization of agricultural straw is crucial for improving soil fertility and reducing greenhouse gas emissions (GHGs). The purpose of this study was to investigate how rice (RB) and maize (MB) straw-derived biochar, produced at varying pyrolysis temperatures and application rates, regulated straw decomposition and GHGs by reshaping soil microbial communities and physicochemical properties. Through 90-day incubation experiments, it was found that biochar produced using low temperature (300 °C) at 2.5–5.0% application rates significantly accelerated straw decomposition by 14.94–36.04% and reduced CH₄ and N₂O emissions by up to 37.84–90.26% and 41.60–91.10%, respectively. Application of biochar produced using low-temperature method enhanced the soil organic matter (9.92–29.26%), pH (1.82–11.32%), and soil enzyme activities (cellulase: 7.84–22.90%, β-glucosidase: 49.92–75.32%), while altering microbial communities, especially increasing copiotrophic bacteria (e.g., Proteobacteria, Ascomycota) in rice grown soils linked to rapid decomposition and reducing Ascomycota dominance in maize soil with altering nutrient dynamics due to higher C/N ratios. Path analysis indicated strong biochar–enzyme–decomposition linkages (normalized coefficient: 0.92), emphasizing microbial community structure as a pivotal mediator. In contrast, biochar produced through high pyrolysis temperatures (mentioning the temperature) diminished effectiveness due to higher structural stability and potential limitations in microbial activity. Our results indicate that application rates of 2.5–5.0% biochar produced through low temperature can effectively balance straw decomposition and GHGs reduction, offering a sustainable approach for straw management in rice and maize cultivation. These findings provide scientific support for optimizing biochar use in agriculture, contributing to improved soil health and climate change mitigation.