Objective To systematically investigate the influence of different cropping patterns on soil physicochemical properties and microbial community structure, elucidate the relationship between soil microbial composition and nutrient factors, and comprehensively evaluate the integrated effects of mustard-rice, mustard-sorghum and mustard-tobacco on the farmland ecosystem.

Method Soil samples were collected from plots under different cropping patterns, and their physicochemical properties were measured. The Illumina MiSeq high-throughput sequencing platform was employed to analyze the community structures of soil fungi and bacteria. Statistical methods were further applied to explore the correlations between soil microbial community composition and soil nutrients.

Result The soil physicochemical indicators under the mustard-rice pattern were generally lower than those in the other treatments, with total phosphorus, available phosphorus, available potassium, and pH significantly lower than those in the mustard-sorghum and mustard-tobacco patterns. The Shannon indices for soil fungi and bacteria under the mustard-rice pattern were 4.28 and 7.03, respectively, both significantly higher than the other two patterns. Ascomycota was the dominant fungal across all three cropping patterns on phylum level, while Pseudomonadota was the dominant bacterial in the mustard-rice and mustard-tobacco patterns, and Acidobacteriota in the mustard-sorghum pattern. The mustard-sorghum pattern facilitated the enrichment of Basidiomycota fungi, whereas the mustard- tobacco pattern promoted the enrichment of beneficial fungi in the Mortierellomycota phylum. Correlation analysis revealed significant associations between the community structures of soil fungi and bacteria and total potassium, total phosphorus, available phosphorus, available potassium, total nitrogen, and organic matter. Specifically, 7, 6, and 4 fungal were significantly correlated with soil total phosphorus, total nitrogen, and organic matter, respectively. There were 7, 5, 4, 3, 2, and 1 bacterial phylum showed significant correlations with total phosphorus, available potassium, available phosphorus, total nitrogen, total potassium, and organic matter, respectively.

Conclusion Different cropping patterns not only significantly influenced soil physicochemical properties but also regulated microbial community structure and abundance. The mustard-rice pattern was more conducive to maintaining soil microecological balance. Soil phosphorus and potassium content was identified as a key physicochemical factor driving variations in microbial community structure. In agricultural practice, appropriate crop combinations can be selected based on specific needs to rationally configure responsive crops. This approach aims to fully leverage the ecological functions of diversified rotations while ensuring stable and high crop yields.