Effects of Phosphate Solubilizing Microorganisms on Wheat Yield and Phosphatase Activity

PHOSPHATE solubilizing capacity of four strains, Pseudomonas fluorescence, Bacillus megaterium, Serratia marcescens, and Bacillus subtilis was assessed in liquid National Botanical Research Institute’s phosphate medium containing rock phosphate (RP). A greenhouse pot experiment was conducted to evaluate the effects of inoculation with arbuscular mycorrhizal (AM) fungi alone or in combination with each strain with and without RP on wheat (Triticum aestivum Gemeza-9) growth, yield, nutrient uptake and the activity of alkaline phosphatase. The amounts of P released from RP by bacterial strains ranged from 0.22 to 80.8mg P L-1 and the pH values of the cultures were reduced from initial value of 7.3 to values varied between 4.04 and 6.62. The results indicated that B. subtilis was the most effective strain in solubilizing RP in liquid culture. The combined inoculation with bacterial strains and AM fungi led to a significant increase in soil P content and alkaline phosphatase activity compared with both the non-inoculated and the individually inoculated soil, and this increase was much higher after 69 days comparing with those after 130 days. In RP-amended soil, B. subtilis and P. fluorescence were more effective in increasing NPK uptake of wheat straw and grains compared with S. marcescens and B. megaterium when inoculated with AM fungi. This study is concluded that the combined inoculation plus RP gave better results for wheat grown in sandy soil. Further researches are required to estimate this study under field conditions and different soils to give reliable results.