Isolation, Evaluation and Characterization of Phosphate Solubilizing Bacteria Associated with Soybean in Major Growing Agroecologies of Ethiopia

Phosphorus (P) is often found in forms that are inaccessible to plants, as it forms precipitates with cations or is locked in phosphorylated organic compounds. Phosphate solubilizing microorganisms have been considered as options to alleviate a deficiency of plant-available P in soils, and this experiment is conducted to make use of this microbial potential in Ethiopia where acid soils are rampant. Five phosphate solubilizing bacteria associated with soybean rhizosphere were isolated on culture media and their P dissolution efficiencies were quantified on solid and liquid media containing insoluble Ca, Fe, and Al. The isolates were genetically characterized using their 16S-23S rRNA region. Three of the best P dissolving strains were field evaluated in six different areas of Ethiopia. The isolates demonstrated P dissolving capacities. One of the isolates was from Pseudomonas genera while the rest were from Bacillus. Inoculation with EPS1, Pseudomonas fluorescens, in combination with Bradyrhizobium (MAR 1495), led to an average of 17.2% yield increase across 6 test locations. This was greater than the yield obtained with the application of half of the recommended inorganic phosphorus fertilizer rate plus Bradyrhizobium, MAR 1495 (average 10.4% yield increase). Phosphorus solubilizing microbes appear to provide an option for improving plant P uptake.