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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 (2.6103 g-1soil) and the least at Molale (15 g-1soil). 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-105, Meh-008, Meh-101, Meh-303 and Meh-305. The phosphate solubilizing efficiency of these five isolates along with Jim-41 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 0.01) solubilized a higher amount of TCP, ERP and OB over the uninoculated control. The highest amount of solubilization was achieved for TCP with Meh-305 (39 mg per 50 ml) followed by ERP with Meh-101 (31 mg per 50ml) at pH 3.82 and 3, respectively. Although Meh-008 and Jim-41 isolates solubilized significant amount of BRP during the 20 days of incubation, the soluble P obtained was very small as compared to other P source tested.

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Density of Rhizobium population in faba bean (Vicia faba L.) fields of Wollo area (Asketema, Gashana, Kotem, Major and Sekota) northern Ethiopia was studied. The highest population of rhizobia was found at Major and the least at Sekota regions. The native rhizobial strains isolated from the northern parts of the country tolerated a higher salt concentration (5% NaCl) than the exotic rhizobial strains (Tall 1402 and Tall 1397). Both native and exotic strains failed to grow at pH 4 and 4.5 levels in the laboratory conditions. In the soil adjusted to pH 4-7, all the native rhizobial strains persisted while those of the exotic strain failed to survive at pHs below 5.5. The native strains were more versatile than the exotic ones in utilizing different carbohydrates as a sole carbon source and were found to be more resistant to many antibiotics (streptomycin, chloramphenicol, rimfampenicillin, oxytetracycline, penicillin and tetracycline) than the exotic strains which are found resistant to chloaramphenicol only. Percentage of nitrogen fixation is also higher for native rhizobial strains these isolates being found to be superior to the exotic strains in stimulating growth, dry matter yield, nodulation and nodule wet weight of faba bean in pouch culture.