Objective As a typical tobacco-growing region with acidic red soil in Miyi County, Panzhihua, low soil phosphorus (P) availability is a key constraint on tobacco production. This study aimed to investigate the succession pattern of the phoC bacterial community in tobacco-growing soils across different altitudes and analyze its intrinsic relationship with soil P transformation and key physicochemical factors, thereby to provide a theoretical basis for precise P regulation and scientific fertilization in regional tobacco cultivation.

Method Soil samples were collected from the low (1600 m), middle (1800 m), and high (2000 m) altitude tobacco fields in Miyi County, Panzhihua. Sequential extraction and Bowman-Cole methods were used to determine various inorganic P (Al-P, Fe-P, Ca-P, O-P) and organic P (labile, moderately labile, moderately stable, and highly stable) fractions, respectively. Soil physicochemical properties were analyzed, and amplicon sequencing was employed to assess the diversity and composition of the phoC gene community. Key driving factors were identified.

Result Soils at all three altitudes were acidic. With increasing altitude, soil organic carbon (SOC), total nitrogen (TN), alkali-hydrolyzable nitrogen (AN), available P (AP), total organic P (TOP), and moderately stable organic P (MSOP) contents first decreased and then increased. Total potassium (TK) decreased, while total P (TP), water content (WC), AK, TOP, labile organic P (LOP), and moderately labile organic P (MLOP) contents increased. The diversity of the phoC gene community was the highest at the middle altitude, followed by the high altitude, and the lowest at the low altitude. Proteobacteria was the dominant phylum. At the middle altitude, Stenotrophomonas was the predominant genus, whereas Klebsiella and Xanthomonas were dominant at the high altitude. The phoC gene community structure varied significantly with altitude, showing the greatest differences at the middle altitude. Redundancy analysis indicated that MSOP and AN were the most significant factors influencing the phoC community composition.

Conclusion This study demonstrated that both P fractions and phoC bacterial community structure in Panzhihua tobacco-growing soils exhibited clear altitudinal variations, driven primarily by MSOP and AN. The middle altitude, despite having the lowest AP, showed the highest diversity and richness of phoC bacteria, indicating that P-solubilizing microbes at this altitude enhanced organic P mineralization in response to low P stress. These findings provided a theoretical basis for optimizing P fertilizer application in local tobacco cultivation.