The beneficial effect of applying carrier based inoculum of one highly potent rhizospheric phosphate solubilizing and N₂ fixing strain of Azotobacter sp. R12 on two rice varieties was assessed. The strain solubilized about 61% rock phosphate in 3 days and produced 2-keto-gluconic acid as the active principle for solubilization. The rice varieties were medium grained MTU 7029 (Swarna massouri ) of rainy season (Aman) and a fine grained IET 4094 (Khitish) for summer season (Boro) are described . The effect of bacteria was tested with the application of different doses of phosphate and nitrogen. The growth, nitrogen content, weight of thousand grains, chlorophyll content, and yield of the crops were remarkably increased with application of the strain. The strain R12 showed its best performance at zero level of P₂O₅ and N₂. In the presence of high level of P₂O₅ and N₂ beyond the recommended dose the performance of the isolate was not satisfactory. The strain was applied to the crop field by seed-inoculation, seedling-inoculation and twice subsequent application of carrier-based inoculum at the intervals of fifteen days.