Increasing phosphorus (P) use efficiency in agricultural systems is urgent and essential to significantly reduce the global demand for this nutrient. Applying phosphate-solubilizing and plant growth-promoting bacteria in the rhizosphere represents a strategy worthy of attention. In this context, the present work aimed to select and validate bacterial strains capable of solubilizing phosphorous and promoting maize growth, aiming to develop a microbial inoculant to be used in Brazilian agriculture. Bacterial strains from the maize rhizosphere were evaluated based on their ability to solubilize phosphate and produce indole acetic acid. Based on these characteristics, 24 strains were selected to be further evaluated under laboratory, greenhouse, and field conditions. Among the selected strains, four (I04, I12, I13, and I17) showed a high potential to increase maize root growth and shoot P content. Strains I13 (Ag87) and I17 (Ag94) were identified by genomic sequencing as Bacillus megaterium and Lysinibacillus sp., respectively. These strains presented superior yield increments relative to the control treatment with 30% P. In addition, combining Ag87 and Ag94 resulted in even higher yield gains, indicating a synergistic effect that could be harnessed in a commercial inoculant for Brazilian agriculture.

Low phosphorus (P) availability in tropical soils is one of the main constraints to agricultural productivity and the sustainability of cropping systems. In this study, we evaluated the functional potential of four bacterial strains, including those present in two commercial inoculants: Nodubiophos (Ag87-CCT 8090 and Ag94-CCT 8108), and Biomaphos (B119 and B2084), focusing on their production of phosphatase and phytase enzymes, organic acids, and their agronomic efficacy in soybean cultivation. In vitro assays showed that all strains exhibited phytase and both acid and alkaline phosphatase activities, with B2084 and Ag94 standing out in phytase-mediated mineralization. In contrast, B119 and B2084 showed the highest phosphatase activity. Organic acid production varied among strains and was influenced by the phosphate source, indicating a highly responsive metabolic regulation. Strains Ag87 and Ag94 were particularly effective in producing lactic, malic, and gluconic acids, displaying distinct profiles modulated by the available P source. In field trials, combined inoculation with Ag87 and Ag94 led to increased soybean yield, achieving performance comparable to conventional fertilization at 50% and 100% of the recommended P rate, despite applying only 30% of the total P. The results highlight complementary metabolic strategies among the evaluated strains, with the ability to solubilize and mineralize phosphorus through different mechanisms. They support their potential use as bioinoculants to enhance nutrient use efficiency and reduce fertilizer dependency in soybean cultivation.