Impact of various fertilizers on the assembly of soil microbial community structure

Soil microbial communities play a pivotal role in ecosystem function and agricultural sustainability. However, how different fertilization regimes shape microbial community structure and assembly remains insufficiently understood. In this study, a controlled microcosm experiment was conducted to compare the effects of castor cake, chemical fertilizer, and cattle manure on soil bacterial communities across multiple stages. High-throughput 16S rRNA gene sequencing combined with multivariate statistical analyses, ecological modeling, and co-occurrence network analysis was used to comprehensively evaluate changes in microbial diversity, composition, functional associations, and assembly mechanisms. The results revealed that castor cake application significantly enriched beneficial phyla such as Actinomycetota and Bacillota, enhanced alpha-diversity, and induced pronounced shifts in community composition. Compared to other treatments, castor cake also triggered stronger nutrient-enzyme-microbe interactions, stimulated modular and complex microbial networks, and shifted community assembly processes from deterministic filtering to stochastic stabilization over time. These findings suggest that castor cake not only supports microbial community recovery and ecosystem resilience, but also holds substantial potential as a sustainable organic fertilizer for improving soil health and microecological stability.