Phosphate solubilizing activity of native soil microorganisms from the rhizosphere of Jatropha curcas and from phosphate-solubilizing bacteria inoculum

Phosphorus is one of the most vital macronutrients required for growth and development of plants. A large number of microorganisms in the rhizosphere are known to solubilize and make available insoluble phosphorus, transforming it into phosphorus available to plants. We evaluated the phosphate solubilizing activity of native microbiota and phosphate solubilizing bacteria in rhizospheric soil with or without added rock dust (mainly granite dust) for enhancing growth of Jatropha curcas, an important plant for biodiesel production. The experiments were performed in a greenhouse with a random statistical design with 14 replicates. The soil received varying dosages of rock dust. Resident microorganism concentrations were measured, along with phosphorus content and enzymatic activity with focus on phosphatase, for 240 days. The highest content of phosphorus, 2.49, and dry biomass occurred in the presence of only soil-resident microbiota until 120 days, 70.45 in leaves; 73,98, in roots, and 105.44, in stalks. Soil samples under the influence of only resident microbiota had the highest enzymatic activity. The highest values were observed for acid phosphatase activity. Phosphatases showed values of 130.69 mu g at 30 days, 155 mu g, at 120 days, and 122.62 mu g of p-nitrophenol.g(-1)soil.h(-1), at 210 days. Added rock dust and phosphate solubilizing bacteria did not improve plant growth.