PSB culture contains millions of Soil Phosphate Solubilising Micro-Organisms/gm. They stay near the roots & make phosphorus available to plants from soil as well as fertilizers & increase the production significantly.
Phosphorus solubilizing activity is determined by the ability of microbes to release metabolites such as organic acid (lactic acid, malic acid, gluconic acid, fumaric acid, succinic and acetic acid.
Phosphorus solubilizing ability of PSB has direct correlation with pH of the medium.