Unraveling the potential of native Azotobacter and Azospirillum spp. formulations for sustainable crop production of rice (Oryza sativa L. var. Khandagiri).

• Biological nitrogen fixation is a sustainable approach for boosting growth of rice and reducing the burden of chemical fertilizers • Azotobacter and Azospirillum spp. isolates (Az2 & As5) from native soil showed promising PGP functions • The isolates Az2 and As5 showed significantly higher N 2 -ase activity and fixed more nitrogen • Combined application of Azotobacter and Azospirillum spp. isolates (Az2 & As5) promoted the growth and development of rice (Oryza sativa L. var. Khandagiri) Biological nitrogen fixation is significantly effective and sustainable field procedure for the promotion of plant growth & development and reducing the burden of chemical fertilizers. In the present investigation, plant growth promoting activities of indigenous bio-fertilizer formulations of Azotobacter and Azospirillum spp. isolated from rice pots filled with local soil of Odisha was examined. The efficacy of Azotobacter and Azospirillum spp. were assessed by selecting five isolates from each genus that were analyzed by biochemical assay like utilization and fermentation of carbohydrate, citrate, nitrate reduction activity, oxidase activity, catalase activity and phosphatase activity. The isolates (Az2 and As5) showed maximum PGP activities among all the isolates of Azotobacter and Azospirillum spp. The analyzed isolates showed variation in production of ethylene between 63.11 ± 4.23 to 121.09 ± 4.56 nmole C 2 H 4 /mg bact./h. The isolates Az2 and As5 among Azotobacter and Azospirillum spp. respectively fixed more nitrogen in culture which is 101.66 ± 9.79 (Az2) nmole and 121.09 ± 4.56 (As5) nmole C 2 H 4 /mg bact./h. The treatments T 1 (Az2) and T 2 (As5) were used as individual application of Azotobacter and Azospirillum spp. and T 3 as combined application of both the strains which had the best response in all of the developmental metrics studied. Among all treatments, T 3 performed around 23-27% better than the T 1 and T 2 individually. [ABSTRACT FROM AUTHOR]