Differences in Soil Nutrients in Sichuan Tobacco-growing Areas and Their Effects on Microbial Community

Purpose To investigate the differences of topsoil nutrients in typical tobacco-growing areas of Sichuan, and to conduct an in-depth analysis of their effects on the structure and diversity of soil bacterial and fungal communities, providing a scientific basis for soil ecological management and the production of high-quality tobacco leaves.

Methods A total of 10 representative tobacco-growing areas in Sichuan, Huili, Yanyuan, Dechang, Mianning, Huidong, Gulin, Xuyong, Renhe, Yanbian, and Miyi, were selected as research areas. Soil properties, including nitrogen, phosphorus, potassium, organic matter, pH, bulk density, and field water-holding capacity, were measured in the topsoil. High-throughput sequencing was used to analyze the composition and diversity of bacterial and fungal communities and their relationships with environmental factors.

Results Significant differences in soil physicochemical properties were observed among different tobacco-growing areas. Total nitrogen (0.94-1.88 g/kg), total phosphorus (0.61-2.06 g/kg), total potassium (8.64-21.08 g/kg), alkali-hydrolyzable nitrogen (60.94-158.09 mg/kg), available phosphorus (22.91-155.06 mg/kg), and available potassium (141.27-489.33 mg/kg) content showed pronounced spatial heterogeneity. Exchangeable calcium and exchangeable magnesium were generally high. Soil pH ranged from 5.20 to 7.49, mostly acidic; and organic matter content (15.40-34.03 g/kg) was at suitable levels. Topsoil bulk density ranged from 1.18 to 1.38 g/cm³, and field water-holding capacity from 16.33% to 24.55%. Soil bacterial diversity was high (Shannon index was 6.06-6.46), while fungal diversity was relatively low (Shannon index was 3.83-4.29), and there was a certain difference in the α-diversity between the two communities. Principal co-ordinates analysis showed that there were significant differences in the bacterial and fungal community structures among different tobacco-growing areas (P=0.001). Dominant bacterial phyla included Proteobacteria, Acidobacteriota, and Actinobacteriota, while dominant fungal phyla included Ascomycota, Mucoromycota, and Basidiomycota. Redundancy analysis demonstrated that soil physicochemical factors significantly driven the shifts in bacterial and fungal community structures, with total nitrogen, total phosphorus, total potassium, available phosphorus, available potassium, exchangeable calcium, exchangeable magnesium, pH, and organic matter identified as key environmental drivers.

Conclusion The soils in typical tobacco-growing areas of Sichuan exhibit significant spatial heterogeneity in nutrient distribution, and the soil physicochemical properties significantly influence the structure and diversity of microbial communities.