Exploring Phosphate-Solubilizing Bacteria In Paddy Rhizospheres Across Varied Management Systems

Phosphate-solubilizing bacteria (PSB) from diverse paddy field management systems are promising candidates for use as biofilm-based biofertilizers. This study aimed to identify PSB isolates with superior phosphate-solubilizing capacity and to examine soil factors influencing this ability. Bacterial inoculants were isolated from paddy rhizospheres managed under conventional, semi-organic, and organic systems with different durations: 7, 10, and 15 years of organic practice. All fields were located in Inceptisols of Mojogedang, Karanganyar, Indonesia. Results showed that the management systems significantly affected the total bacterial population density. From the total bacterial colonies, 15 isolates were identified as capable of solubilizing phosphate. The 15-year organic farming system (Organic 2009) showed the highest bacterial population (1.24 × 10¹⁸ CFU/g), while the lowest was observed in the semi-organic system (1.19 × 10¹⁵ CFU/g). The isolate R5 had the highest phosphate solubilization index (PSI) of 5.10, followed by R7 (3.35) and R13 (3.13), while R8 had the lowest (2.12). The result of correlation analysis revealed that organic carbon (r = 0.56*) and available phosphorus (r = 0.83*) were positively correlated with the solubilization index. These PSB isolates have promising potential for the development of innovative biofilm-based biofertilizer formulations.