Isolation and Identification of Phosphorus Solubilizing Bacteria from Soil and Tomato Rhizosphere in Iree Town, Osunstate

ABSTRACT Phosphorus (P) is a critical macronutrient essential for plant growth, playing key roles in energy transfer, root development, and photosynthesis. However, despite its abundance, phosphorus often exists in insoluble forms in soil, making it unavailable to plants. This study aimed to assess the physicochemical and microbiological properties of phosphorus-solubilizing bacteria (PSB) in soil and the tomato rhizosphere in Iree, Osun State, Nigeria. Soil samples were collected from Campus, Eyinade and Baptist area before and after planting to evaluate pH, temperature, and bacterial counts. Initial pH values ranged from 8.2 to 8.8, while post-planting samples showed a slight decrease to a range of 8.4 to 8.6, likely due to acid production by PSB. Bacterial counts decreased after planting, with the highest count observed at 4.3 x 10⁶ CFU/g in campus soil before planting, which dropped to 1.8 x 10⁶ CFU/g post planting. The PSB isolates were identified and characterized based on colonial, morphological, and biochemical features, with predominant bacteria including Bacillus spp., Pseudomonas putida, Enterococcus spp., and Alcaligenes spp., known for their phosphorus-solubilizing abilities. Bacillus spp. and Pseudomonas putida showed significant potential for improving phosphorus bioavailability, supporting existing research on their role in sustainable agriculture. This study highlights the effectiveness of using PSB as biofertilizers, as their natural solubilizing mechanisms reduce the need for chemical fertilizers, mitigate environmental risks, and promote sustainable agricultural practices. Future research should explore large-scale applications and interactions between PSB and different crops to enhance nutrient uptake and optimize crop yields. Keywords: Phosphorus, planting, bacteria, solubilizing, tomato, rhizosphere, phosphorus-solubilizing