Literature analysis and chemical considerations of biological phosphate solubilization have shown that the commonly used selection factor for this trait, tricalcium phosphate (TCP), is relatively weak and unreliable as a universal selection factor for isolating and testing
phosphate-solubilizing bacteria (PSB) for enhancing plant growth. Most publications describing isolation of PSB employed TCP. The use of TCP usually yields many (up to several thousands per study) isolates “supposedly” PSB. When these isolates are further tested for direct contribution
of phosphorus to the plants, only a very few are true PSB.