A. Keneni - Department of Applied Biology, Ambo University College, Ambo, Ethiopia.
F. Assefa - Department of Biology, Addis Ababa University, Addis Ababa, Ethiopia.
P. C. Prabu - Department of Applied Biology, Ambo University College, Ambo, Ethiopia.

Native phosphate solubilizing bacteria (PSB) were isolated from four areas (Ankober, Keyt, Mehalmeda and Molale) of Ethiopia to study their effect on releases of soluble phosphorus from insoluble P sources. The highest bacterial number was found at Keyt (۲.۶۱۰۳ g-۱soil) and the least at Molale (۱۵ g-۱soil). Five efficient PSB were selected for further study based on their ability in forming a higher clear zone diameter than the other isolates. These isolates were identified based on phenotypic characters as Pseudomonas sp. Anb-۱۰۵, Meh-۰۰۸, Meh-۱۰۱, Meh-۳۰۳ and Meh-۳۰۵. The phosphate solubilizing efficiency of these five isolates along with Jim-۴۱ isolate from the National Soil Research Centre were studied using different P sources [Tricalcium Phosphate (TCP), Egyptian Rock Phosphate (ERP), Bikilal Rock Phosphate (BRP) and Old Bone meal (OB)] in an incubation study. The results revealed that all the PSB isolates significantly (P ۰.۰۱) solubilized a higher amount of TCP, ERP and OB over the uninoculated control. The highest amount of solubilization was achieved for TCP with Meh-۳۰۵ (۳۹ mg per ۵۰ ml) followed by ERP with Meh-۱۰۱ (۳۱ mg per ۵۰ml) at pH ۳.۸۲ and ۳, respectively. Although Meh-۰۰۸ and Jim-۴۱ isolates solubilized significant amount of BRP during the ۲۰ days of incubation, the soluble P obtained was very small as compared to other P source tested.

Ethiopia, Insoluble phosphorus, Phosphate solubilizing bacteria, Soluble phosphorus