Characteristics Of Phosphate Solubilizing Bacteria And Its Benefits Growth And Quality Of Red Clover

Phosphate-solubilizing bacteria is important for agriculture, because it increases available phosphorus in soils, improving nodulation and nitrogen fixation of rhizobia, secreting plant auxin, enhancing the systemic resistance of plant. In the present paper, 45 bacteria strains were screened from the rhizosphere of clover (Trifolium pratense, Trifolium repens) on PKO or Mongolia Jin. Their ability of solubilizing phosphate was researched by the methods of Phosphate-solubilizing cycle and molybdenum blue. The ability of secreting plant anxin was researched by colorimetry. The effects of the growth characters of red clover(Trifolium pratense L.)and nutrition of N,P, from 4 bacteria strains and their combination was researched by pot test. The results as follows:1)There were strains of Phosphate-solubilizing. There amount of phosphate-dissolving microorganisms in different section of the plant rhizosphere was different, the distribution trend present as RS>RP>NRS>HP. 70% bacteria strains were situated in the soil adhering to roots and rhizoplan or surface of roots, few of them in the root. 45 strains had been obtained, among which, 23 strains have the ability of solubilizing phosphate (8 strains on red clover, 15 strains on white clover), and in which 10 strains had both ability of solubilize inorganic phosphate and dissolve organic phosphate. In liquid culture, the available phosphate increment changed from 5.0 mg/L to 666.0 mg/L of inorganic phosphate-solubilizing bacteria and 0.39 mg/L to 58.34 mg/L of organic phosphate-solubilizing bacteria with molybdenum blue method. 21 strains could product auxin(IAA), but the ability was quite different, 10 strains were the strain of phosphate–solubilizing among of the 21 strains. The IAA concentration on the culture medium changed from 0.003 mg/L to 23.873 mg/L.The pH had a very different influence on the ability of solubilizing phosphate. In PKO culture medium, the pH of lhs4 reduced 2.54 comparing to the control, the available phosphorus increment increased 556.3 mg/L than the control. The phenomenon between available phosphorus increment and total organic acid was similar to the pH. The available phosphorus increment of bacteria strains had no correlation with pH and total organic acid. on the Mongolia Jin, the available phosphorus increment is related to pH, but with the same pH,its amount was quite different.3)Some treatments could secret organic acid, but the nature and amount were quite different. The culture mediums include acetic acid by all activation treatments. The oxalic acid, tartaric acid and lactic acid were found in the PKO culture medium by most treatments. The amount of organic acid was different by different activation treatments, such as acetic acid, it ranged from 41.597 mg/L to 237.909 mg/L. The amount of organic acid by different treatments was different. The medium culture of inactivation treatments were detected citric acid, such as the treatment of lhs11',ls3-5',lhs8'and Hsg'. The amount of organic acid by partial inactivation treatments was higher than the control, the malic acid on medium culture of Ls2-13'. This result showed that the cells of bacteria contain with different nature of organic acid. The total organic acid increased by activation treatments of ls2-13,ls3-5,lhs8 and than the control.The available phosphate increment were more than 100 mg/L by activation treatments, and its amount were range from 53.8 mg/L to 124.2 mg/L by inactivation treatments, That results showed the organic acid had an influence on the available phosphate increment. The effect from strong to weak presented as oxalic acid or tartaric acid>tartaric acid or malic acid>Acetic acid, but the activation strain treatment of lhs6 was not consistent with the above result.4)The available phosphate increments were obvious different on the culture medium by each treatments. The available phosphate increment was from 14.6 mg/L to 307.6 mg/L on the PKO by single strain. The Rhizobium could solubilize the inorganic phosphate, but it was lower than the solubilize phosphate bacteria. The available phosphate increment of admixture strains among AD, AB and BD presented the result of 1+1>2. On the strain combination of ACD, its available phosphate increment was quite higher than the single strain, but the effect was not signed 1+1+1>3. On the Mongolia Jin culture medium, the D was the most effective one of all the single strain, the available phosphate increment was 11.11 mg/L. The Rhizobium could solubilize the organic phosphate, but its ability is weaker than the ability of solubilize organic phosphate bacteria. In all strain combinations, only admixture strains AC, its available phosphate increment was higher than the single strain, but it was not an additive effect.5)The single strain or strain combination all had an effect on the pH and total organic acid on the culture medium. In treatments of C and ABD, although the pH was large, the available phosphate increment was high too. The treatment of B, the pH was large,but the available phosphate increment was low. The ability of dissolving phosphate was not related to pH (PKO and Mongolia Jin) and total organic acid (PKO) directly culture medium by all treatments.6)The single strain or strain combination all could product plant auxin, but the amount of plant auxin was obvious different. Ttreatments by combined every two strains, the combination AD presented the result of 1+1>2. Compared to sum of plant auxin of A and D incubated alone, the total plant auxin of the combination was enhanced 79.54%. The combinations between B and the other strains, the amount of plant auxin were lower than the strain of B. the reduction changeed from 14.06% to 47.43%. The plant auxin of combination ABCD were enhanced 59.06% compared to A.7)Each strain treatments had an influence on the growth quality of red clover, such as height, roots length, above-ground biomass, underground biomass. The growth quality of different treatments was quite different. For the height of red clover, the single strain was best; the combination of two strains was next. The result was contrary to the roots length, above-ground biomass, and underground biomass. The absorption pf phosphorous by treatments A, AC, AD, BC and BCD was more than the control. The phosphorous of other treatments was lower than the control, but there were not significantly different.Comprehensive analysis of the influence of each treatment, the single strain of A was best. In combination of two strains, AD had the significant effect on the growth.The percentage separately increased 19.23, 86.07, 3.94 and 151.33. In the ACD, the height of red clover increased 5.28%. The above-groud biomass increased 83.14%. The roots length reduced 9.82%. The underground biomass increased 118.43%. The crude protein of red clover by the treatment of ABCD and BCD separately increased 14.63% and 1.38% than the control. The phosphrous of red clover by the treatment of ABCD increased 5.22% than the control. The result of above-groud biomass and the crude protein, the treatment of CD had a quite effect. The crude protein is 21.21%, the above-groud biomass increase 85.15% than the control. It showed great potential for agriculture use and should be study further.