Effect of moisture level and rock phosphate on soluble P at the presence of phosphorus solubilizing fungi during time

Dissolution of phosphate by P solubilizing microorganisms is dependent on the environmental conditions and the composition of the medium culture. Present study conducted to investigate the effect of two fungal species, moisture content and rock phosphate content on water soluble phosphate (WSP), pH and changes of medium weight with time. Two fungi Aspergillus niger and one isolate from rock phosphate mine mountain Laar used as P solubilizing fungi. The experiment performed as factorial in a completely randomized design with three rock phosphate (RP) levels (zero, 1:8 and 1:4 RP: rice husk), two levels of moisture content (100 and 200% w/w) and fungi at three levels (control, the isolate and A. niger) with three replications for 60 days. At 10, 30 and 60 days after incubation WSP, pH and mass reduction of culture medium were measured. Results showed that presence of RP not only did not increase but even decreased WSP. Genrally, WSP increased with moisture increase to 200%. The highest WSP achieved in the presence of A. niger on 200% moisture level and 1:8 RP. Water soluble P showed a decreasing trend in the presence of the isolate though it had a higher growth than A. niger. The trend of pH changes were similar to WSP which increased as pH decreased. Results of the present study suggest that medium composition and condition is important on P solubilization and need more attention.