Abstract

Bacterial strains isolated from green house soils were incubated in vitro for seven days to assess their phosphate solubilizing capacity, solubilization index, organic acid production and acid and alkaline phosphatase activity. All the tested isolates solubilized inorganic phosphates in varying degrees in NBRIP liquid culture medium. Acidification by means of producing organic acids may be the key mechanism attributed to increased phosphate solubilization as revealed by the strong negative correlation (r = - 0.923 ± 0.1, P ≤ 0.05) observed between the amount of phosphorus released and pH in the culture medium. Moreover, acid and alkaline phosphatase released by the isolates may also have certain contribution to phosphate solubilization. Gluconic acid was the most common acid produced by isolated organisms followed by citric and oxalic acid. Out of the isolates, strains PSB–1(Pantoea agglomerans), PSB–5 (Burkholderia anthina) and PSB–8 (Enterobacter ludwigii) solubilized significantly higher amount of inorganic phosphate within a day, exhibiting their higher potential to be used as soil inoculants to enhance soil fertility and plant growth.

Key words: Organic acids, phosphatase activity, solubilization index, phosphate solubilization.