the effect of thiobacillus and aspergillus on phosphorous availability of enriched rock phosphate with sulfur and vermicompost

abstract a large number of studies have shown that direct application of rock phosphate dose do not have enough efficiency to release phosphorus compared to chemical fertilizers. the main purpose of this study was to increase the efficiency of direct application of rock phosphate. incorporation of rock phosphate with sulfur, organic matter and inoculation with sulfur-oxidizing bacteria and phosphorous-solubilizing fungus, seems to be a suitable alternative for increasing the efficiency and applicability of rock phosphate. this experiment was carried out in laboratory condition, using completely randomized factorial design with 12 treatments and 3 replications. the treatments included sulfur at three rates, 0% (s0), 10% (s1), 20% (s2), vermicompost at two rates, 0% (v0), 15% (v15), and inoculation with thiobacillus thiooxidanc, aspergillus niger (bf) and without inoculation. water soluble phosphorus and ph were measured during incubation time (15 and 60 days). the results of experiment showed that water soluble phosphorous increased over the time and the maximum level of water soluble p was observed using treatment of 20% sulfur, 15% vermicompost and inoculated with thiobacillus and aspergillus (bfs2v1). the amount of water soluble phosphorus in bfs20v15 was significantly higher than other treatments.