Phosphate Solubilizing Bacteria Isolation Medium: Rock Phosphate or Tricalcium Phosphate?

Abstract Phosphorus is one of the essential elements limiting vegetative production in the world. Although phosphorus is abundant in soils, a tiny part is available for plants. With phosphate solubilizing bacteria (PSB), phosphorus, insoluble in soils, is transformed into a suitable form for plants. This study aimed to determine tricalcium phosphate (TCP) activities and rock phosphate (RP) used to isolate PSMs. 118 bacterial isolates, which can phosphate solubilizing, were incubated for 72 h in National Botanical Research Institute phosphate (NBRIP) medium using TCP and RP as phosphate sources. At the end of the incubation, the amount of inorganic phosphorus (Pi) in the medium and the pH of the medium was determined. As a result of bacterial incubation, an average of 57.87 mg L−1 Pi was detected in rock phosphate medium, while this rate was found to be 421 mg L−1 in TCP medium. After 72 h of incubation, it was determined that the pH of the NBRIP media varied between 3.60 and 5.05, and TCP dissolved seven times more to rock phosphate. This study has shown that TCP alone in determining the isolation and effectiveness of PSMs is not indigenous.