Primary Studies On Isolation Of Phosphobacteria In The Rhizosphere Of Alfalfa (Medicago Sativa) And Wheat (Triticum Aestivum) And On Its Effect Of Solubilizing Phosphate

Phosphorus is one of the necessary factors in the life of the plant. Most of our soil in cropland and grassland are P deficient; about 95% P in soil can't be directly used by plant. Although applying P fertilizer in the soil is main way to raise the amount of available P, the applied P fertilizer is often converted into unavailable P by combining with Ca2+(calcareous soil), Fe3+and A13+. In usual, the utilization ratio of P fertilizer only ranges from 5% to 25%. As the result, it is important to convert insoluble P into soluble P and to release P from lecithin. Phosphobacteria related to the conversion, storage and supply of P in soil plays an important role in improving the ability of the soil to supply P. In this research, the phosphate-solubilizing bacteria in plant rhizosphere were separated and characteristically studied for two representative plants in grass and crop-alfalfa and wheat. The result showed that:1. There are 104 isolations have better effect of solubilizing phosphate.89% isolations have better effect on PKO medium.More than 68% microorganisms achieved by separation can solubilize organic P( lecithin) and inorganic P(phosphate of calcium). 17% only solubilize inorganic P, and 15% only solubilize organic P.2. There is different amount of phosphate-dissolving microorganisms in different section of the plant rhizosphere, the distribution in different section present as: RS>NRS>RP>HP. Most number of the bacterial strains are situated in the soil of the plant rhizosphere, only few in the root.3. Most bacterial strains grow fast (in PKO, Mongina organic culture medium and inorganic culture medium, especially in organic P culture medium). Only 21% bacterial strains grow slower (being observed until 72 hours later) ,others grow much faster or just secondary(being observed 12 hours or 24 hours later) .4. Each phosphate-solubilizing microorganism begins to dissolve organic P and inorganic P in different time.94% phosphate-solubilizing microorganisms solubilize inorganic P earlier than organic P. 78% begin to solubilize inorganic P (phosphate of calcium) in 1~2 days, 18% in 3~4 days, only 4% begin 5 days later. 38% phosphate-solubilizing microorganisms begin to solubilize organic P(lecithin) in 1 ? days, 46% in 3~4 days, 16% begin 5 days later after inoculation.5. There is no significant correlation between the increment of available P and the PH of the culture media.The increment of available P in the process of solubilizing organic P (lecithin) and inorganic P (phosphate of calcium) has no correlation with the PH of the culture media, in another word, it does not completely relate to the number of proton in the medium.6. There is great difference between phosphate-dissolving microorganisms' capability ofdissolving rock phosphate and lecithin.30 kinds of phosphate-dissolving microorganisms were included in this research. The increment of available P ranged from 1.06mg/100ml to 6.75mg/100ml by dissolving inorganic P (phosphate of calcium), about 6 isolations increment of available P are higher than 6.00mg/100ml and about 3 isolations are isolated from Medicago rhizosphere. The increment of available P ranged from 0.06 mg/l00ml to 4.44mg/100ml by dissolving organic P (lecithin) ,about 5 isolations increment of available P are higher than l.00mg/l00ml and about 2 isolations are isolated from Medicago rhizosphere.