Comparative Study of Phosphate Solubilizing Bacteria from Paddy Field

Rice (Oryza sativa) is important grain providing one-fifth of caloric requirement of humans globally. Phosphorus is one of the major macronutrients required by plants. But, most of phosphorus present in soil is in insoluble forms and un-utilizable by the plants. Phosphate solubilizing bacteria (PSB) existing in rhizosphere solubilizes insoluble, in-organic and organic phosphorous forms thereby making soluble phosphate retrieved by the plant root from the soil environment. The present work is comparative study on phosphate solubilizing bacteria isolated from rhizosphere of rice plant and from non-rhizospheric soil (bulk soil) of the paddy field during flowering and harvest stage. Total number of PSB isolates obtained from rhizospheric soil is more as compared to bulk soil, 21 and 17 in flowering stage and 14 and 13 from harvest stage samples respectively. Out of total 38 isolates from flowering stage and 27 from harvest stage all have phosphate solubilizing ability in qualitative detection which was then quantified. It has been observed that potential for phosphate solubilization was higher among the isolates from harvest stage (282 g/ml to 705 g/ml) with reference to isolates from flowering stage (186 g/ml to 645 g/ml). Other traits of isolates aiding in nutrient acquisition by plant viz. nitrogen fixing ability and potassium solubilization were also determined.