Mechanisms of Microecology in Promoting the Decomposition of Rapeseed Straw in the Soybean Belt
Straw return often limits subsequent crop growth due to slow decomposition. Intercropping can accelerate this process, but the microbial mechanisms remain unclear. Based on a long-term experiment, we examined two cropping patterns (monocropping and intercropping) and three nitrogen levels. Intercropping increased straw decomposition rate compared to monocropping, with the greatest effect under reduced nitrogen. Intercropping with reduced nitrogen accelerated cellulose and hemicellulose breakdown, converting them into stable soil carbon fractions. Intercropping did not affect microbial alpha diversity but reshaped community structure and composition, enriching key taxa during the early decomposition period. Network analysis showed intercropping enriched decomposition-promoting microbial modules (dominated by Bacteroidota and Actinomycetota), whereas monocropping showed potential antagonistic interactions among modules. In conclusion, intercropping with reduced nitrogen achieves a synergy between rapid straw decomposition and high soybean yield by restructuring the straw-associated microbiome.