Biolonisal efficiency of nitrogen fixation strains isolated from rhizosphere of Poa pratensis

Both acetylene reduction and colorimetric methods were employed to measure nitrogenase activity,the solubilizing phosphorus capability and secretion of plant growth hormone of 21 nitrogen-fixing bacteria strains isolated from Kentucky bluegrass rhizosphere soil samples.The result indicated that the nitrogenase activity of 21 tested nitrogen-fixing bacteria strains were between 39.9 and 227.5 nmol·mL-1·h-1.There were 14 strains (67% of all strains) whose activities were more than 100 nmol·mL-1·h-1.The solubilizing phosphorus intensity of nitrogen-fixing bacteria were between 13.38 μg·mL-1 and 58.21 μg·mL-1.Three of these tested strains-N4,N16 and N20 demonstrated stronger solubilizing phosphorus capability.Eight of these tested strains——N2,N4,N5,N10,N14,N16,N17 and N20 demonstrated strong ability of excreting plant growth hormone were measured.