Culture condition of nitrogen fixation strains isolated from rhizosphere of Kentucky bluegrass

Culture conditions and typical growth curve of eight nitrogen-fixing bacteria strains with strong ability of nitrogenase activity and the solubilizing phosphorus capability isolated from Kentucky bluegrass rhizosphere soil samples were studied. The results showed that the temperature adaptation scope of strains was wide and strains could grow well between 20～40 ℃, with the optimum growth temperature of 25 ℃. The nitrogen fixation strains could grow well in a neutral or slightly alkaline pH condition, with the optimum initial pH range of 7.0 to 7.5. The optimum ventilation volume of strain N4, N5, N10, N16, N17 and N20 were 220 mL, and the optimum ventilation volume of strain N2 and N14 were 200 and 100 mL. Based on the above results, the typical nitrogen-fixing bacteria strains growth curves were determined. Most of the strains entered the logarithmic phase after 2 h. Different strains started the lag phase, the logarithmic phase, the stationary phase and the declining phase at different culture time.