2.2. Bacterial solubilization of FePO4, phosphate rock, and phytate
For the P solubilization experiments we used three insoluble P compounds: FePO4, phosphate rock, and phytate. Ground concentrate phosphate rock [Ca10(PO4)6F2] was obtained from White springs, Florida (Lessl and Ma, 2013). FePO4 as FePO4⋅H2O and phytate as phytic acid sodium salt hydrate from rice (C6H18Na12O24P6) were purchased from Sigma–Aldrich.