The Formulation of Consortium of Phosphate Solubilizing Rhizobacteria with Bradyrhizobium japonicum as Biofertilizer and Their Application to Soybean Plant

Abstract

Phosphate solubilizing rhizobacteria were known for their ability to convert insoluble form of phosphate to the accessible form. The use of rhizobacteria as biofertilizer is one of the most promising biotechnologies to improve plant production. This study was conducted to formulate phosphate solubilizing rhizobacteria (Bacillus sp. Cr and Pseudomonas sp. Crb) coinoculated with Bradyrhizobium japonicum (Bj) and appliance them to soybean plant as biofertilizer. Pikovskaya medium containing tri-calcium phosphate at concentration of 0.5% was used to measure P-solubilizing ability of tested strains. Results revealed that Crb1 is the most powerful P-solublizer using tricalcium phosphate as a P source. It was also observed decreasing in pH along with the increasing of amount of soluble P ranged from -0.96 to -0.42 from initial culture during 72 hours. Isolates of the rhizobacteria (Crb and Cr) were grown in media containing skim milk and molases prior to formulation in peat as a carrier material. The combination of three strains produced 4 packages of inoculants. Each packages was tested for their viability and effectiveness on soybeans in the field. The number of bacterial population after 9 months of storage ranged from 7.5 x 106 to 5.8 x 108 cfu gr-1 of peats. Field experiment showed that treatments designed as F1+NPK and F3+NPK were significantly increased soybean plant growth and mineral uptake compared to untreated control and better than NPK treatment. While F1+NPK and F2+NPK were able to increase soybean productivity.