Effect of phosphate solubilizing bacteria on role of Rhizobium on nodulation by soybean

Abstract

Studies were conducted in laboratory to find out the most effective phosphate solubilizer. The phosphate solubilizing microorganisms were isolated from rhizosphere on Pikovskaya's solid medium by serial dilution. Most efficient phosphate solubilizers were identified on Pikovskaya's solid medium by measuring clear zone around the colony and measurement of pH. The result indicates that Aspergillus awamori among fungi and Pseudomonas striata among bacteria produce large sized clear zones around the colony i.e. (0.5 cm) and change the pH of medium from initial 5.8 to 2.5 and 4.5, respectively. To determine the effect of phosphate solubilizing bacteria on role of Rhizobium on nodulation, nodule dry weight, dry matter of plant, 1000 seed weight and yield a field experiment was conducted with eight treatments i.e. Rhizobium + PSB, Rhizobium, PSB, Full fertilizer dose, Half fertilizer dose, Full fertilizer dose + Rhizobium + PSB, Half fertilizer dose + Rhizobium + PSB and Control. Rhizobium + PSB yielded maximum number of nodules (67.13) and nodule dry weight (107.73 mg) Rhizobium alone showed maximum production of dry matter (3.63 gm). Full fertilizer dose + Rhizobium + PSB gave highest 1000 seed weight (109.92 gm). Half fertilizer dose + Rhizobium + PSB gave highest yield (10.67 q/ha) which was equivalent to yield recorded with Full fertilizer dose + Rhizobium + PSB (10.66 q/ha) and Rhizobium + PSB (10.63 q/ha).