DEVELOPMENT OF A FUNGAL INOCULUM FOR EFFICIENT PHOSPHATE UTILIZATION IN AGRICULTURE

Abstract

With the aim of developing an environment friendly P biofertilizer, phosphate solubilizing fungi (PSF) were isolated from Sri Lankan soil. A total of 12 fungal isolates, showing phosphate solubilizing activities were isolated from bulk and rhizosphere soils of different agro-ecological zones. The best 11 P solubilizers selected  by three levels of screening were further evaluated  for  their efficiency  inphosphate solubilization in Pikovskaya liquid media containing tricalcium phosphate and High Grade Eppawala Rock Phosphate (HERP) using two parameters: solubilized P concentration and media pH due to organic acid production.  In contrast to all isolates being  able to mediate high amount of P solubilization in PVK medium,  they were less efficient in solubilizing HERP in modified PVK medium. Among the 11 PSF, fungal isolate KBF4 accounted for the highest Ca3(PO4)2 solubilization while  KBF2 accounted for the highest HERP solubilization. Acidification of the culture media seemed to be the main mechanism of P solubilization in both media indicating a significant pH decrease of the culture supernatants.  A significant correlation between the quantity of P solubilized and the pH decrease in PVK liquid media containing Ca3(PO4)2 was observed.  This relationship was not significant in HERP medium indicating other possible mechanism of phosphate solubilization.