Isolation and identification of Azotobacter from saline and non-saline soils of Bangladesh

Nitrogen is the most important mineral nutrient required for the plants growth and development. Microbial inoculants have the potential to augment and reduce reliance on expensive chemical fertilizers specially Urea, while maintaining crop productivity. Urea fertilizer not only expensive but also destroy our environment by nitrate pollution. Some microbes have ability to fix atmospheric nitrogen in soil symbiotically in legume crops. However, there are a few reports on non-symbiotic nitrogen fixers for non- leguminous crops. The present study aimed to isolate efficient non symbiotic or free living Azotobacter spp. that could be utilized as potential bio inoculants for resolving the nitrogen deficiency in soil for better growth and development of non-leguminous crops as well as industrial benefits. Nine Azotobacter isolates from saline and non-saline soils of south coastal zones of Bangladesh cultured on Ashby’s agar plates at 28oC for 1 week. The colonies on the medium were picked up and used for the investigations. Based on morphological and biochemical identifications the isolates were confirmed as Azotobacter spp., isolates showed higher nitrogen fixing abilities (6.95 to 9.89 mg N/g) were selected. Among them, isolate NFA3 performed the best (9.89 mg N/g) regardless of all the tests. These isolates could survive neutral to slightly saline soils and higher temperature. Therefore, isolate NFA3 was considered to be the candidate for industrial usage for the development of nitrogenous biofertilizer.