Enumeration, Isolation and Identification of Nitrogen-Fixing Bacterial Strains at Seedling Stage in Rhizosphere of Rice Grown in Non-Calcareous Grey Flood Plain Soil of Bangladesh

Non-symbiotic diazotrophic systems for biological nitrogen fixation (BNF) in agriculture are most promising but the possibility for the extension of nitrogen fixation by rice is still speculative. Accordingly, the present study was conducted for the Enumeration, isolation and identification of nitrogen fixing bacterial strains at seedling stage (30 days after seed sowing) in rhizosphere of rice (BR 10, Oryza sativa L.) grown in Non-Calcareous Grey Flood Plain soil of Bangladesh. The soil is classified as ‘Inceptisol’ order and ‘Aquept’ suborder. It was identified as ‘Dhamrai series’, had ‘silt’ texture, pH 7.1 and 5.5 C/N ratio. The present results of the microbial tests on the rice rhizosphere soil evinced that out of 263 isolates, only 91 were branded as nitrogen fixing organisms per gram of soil, which was about 34.6 % of the total isolates. As per selection criteria, four individual strains were considered for identification. Biochemical tests were conducted for proper identification and the selected strains were identified as Enterobacter spp., Klebsiella spp., Bacillus spp. and Azospirllum spp.