Physicochemical properties of soil and characterization of plant growth-promoting rhizobacteria (PGPR) from legume fields in Kaduna Metropolis, Nigeria

This study explored the physicochemical properties of soils and characterized the plant growth-promoting rhizobacteria (PGPR) associated with the rhizosphere of leguminous crops cowpea and groundnut in Kaduna Metropolis, Nigeria. The soils examined were largely sandy loam and silt loam, with near-neutral pH and moderate to high nutrient contents, particularly phosphorus and nitrogen, which are critical to plant growth. A total of 32 distinct bacterial isolates were recovered, nine of which demonstrated the ability to grow on nitrogen-free medium, indicating potential nitrogen fixation. These isolates also exhibited other growth-promoting traits such as phosphate solubilization, indole acetic acid (IAA) production, siderophore release, and in some cases, hydrogen cyanide synthesis. The predominant genera identified included Bacillus, Pseudomonas, Aeromonas, and Micrococcus, all of which have well-documented roles in enhancing soil fertility and suppressing pathogens. The findings confirm that legume rhizospheres in the study area are reservoirs of functionally diverse and agriculturally beneficial PGPR. This opens up opportunities for developing indigenous, eco-friendly bio-inoculants tailored to local soil and crop needs—an important step toward sustainable agriculture in the region.