The ability of some microbes to solubilize the hardly soluble phosphorous and potassium from various sources in vitro

Abstract

Utilization of bio-fertilizer is an alternative option to maintain the available phosphorus (P) and potassium (K) in the soil. To develop such a bio-fertilizer, the ability of microbes to solubilize phosphate and potassium is one of the most important things. A set of experiments was conducted to evaluate the ability of some microbes (7 bacteria and 7 fungi isolates) to solubilize the hardly soluble P (Ca3PO4, AlPO4, FePO4 and Blora rock phosphate) and K (Malang feldspar) sources in vitro. The results showed that the solubilization rate of hardly soluble P and K sources by microbes are different depending on isolates type and sources applied. The amounts of P released from Ca3PO4, AlPO4, FePO4 and rock phosphate in liquid medium were significantly increased by the isolates, respectively up to 8.8, 69.3, 928, 26 times more than the control (un-inoculated). Some of them also significantly increased the solubility of the K containing mineral (feldspar), up to 2.3 times more than the control. Acidification of the medium has been observed to be the most important mechanism for the P and K solubilization, especially for Ca3PO4, AlPO4. The JK1 fungal isolate was the most promising phosphate-potassium solubilizing microbe.