Investigation of Nitrogen Fixation Efficiency of Some Azotobacter Isolates by Maize Inoculation

Nitrogen fixation ability in free-living condition is one of the properties of diazotrophic bacteria that Azotobacter is one of the famous genera of diazotrophs. Evaluation of nitrogen fixation efficiency can be measured by different methods, such as difference method and plant inoculation. Thus, N2 fixation ability of 18 bacterial isolates such as Azotobacter was measured using completely randomized design with three replications. Bacterial liquid culture was added to bagasse- perlite as a carrier and disinfected seeds were inoculated with prepared inoculants. Treatments were included, negative controls (including carrier without bacteria and without carrier), positive controls (using urea equal to 50% and 100% of fertilizer recommendation) and pots inoculated with bacterial inoculants. Results showed that expect wet weight and nitrogen concentration of root, all measured parameters were significantly influenced by treatments. Other measured parameters such as shoot wet and dry weight, root dry weight, total wet and dry weight, height, diameter and chlorophyll index, were significantly influenced by 50% and 100% fertilizer treatment and highest mean was recorded in these treatments, while among bacterial treatments A. chroococcum 14SP-Ι, A. chroococcum 16SP-2 and Pseudomonas sp. 34SP-Ш were effective. The highest total nitrogen content and nitrogen translocation factor were observed in plants which inoculated by A. chroococcum 16SP-2 that caused an increasing of 32% and 148% compared to negative control (without carrier and bacteria). Also, the highest nitrogen fixation efficiency was measured in 16SP-2 isolate equal to 39.47% by difference method.