Impact of selecting phosphate solubilizing microorganisms on the growth of maize and sorghum using vivianite as inorganic phosphate supply

Phosphate Solubilizing Microorganisms (PSM) were isolated in NBRIP medium containing tricalcium phosphate (TCP) as the sole P source, from roots and rhizospheric soils of Zea mays collected in three localities (Bini, Mbang-boum, Borongo) of the Vina Division of Adamawa Region (Ngaoundéré, Cameroon). Ability of these PSM to solubilize phosphate was tested in modified nutrient agar medium, on 4 inorganic P forms: Ca3(PO4)2, AlPO4.H2O, FePO4.2H2O and vivianite (Phosphate Rock) as natural phosphate source. At least 117 isolates were obtained from roots and soils samples. To conduct test in Reyes basal liquid media, 20 preselected isolates showing excellent solubilizing results in solid medium were selected. Isolates BGL12 (from Borongo soil), BNL (from Bini soil) and RBNBL5 (from Mbang-boum root) successfully solubilize 3 types of phosphate out of 4 used. At the end of the solubilizing process; low pH (pH 4.5) instead of pH 7 in the initial media, revealed the release of organic acid in those media. The isolates RBNBL5, BGL12 and BNL boosted the phosphorus uptake of Zea mays and Sorghum bicolor L. Moench when growth in pot with rock phosphate (vivianite). Increase of the leaves number, the height, the dry biomass and the phosphorus content of these plants was noticed 42 days after planting.