Azotobacter as a Rice Plant (Oryza sativa L.) Growth Promoting Biofertilizer

Today, the use of chemical fertilizers to increase agricultural production has created many environmental problems. In addition, environmental stresses are one of the most important factors reducing crop yield and production. Given the importance of rice plants in ensuring food security nationally and globally and increasing the price of chemical fertilizers, it is necessary to find eco-friendly routes for sustainable agriculture. The use of biofertilizers is the most worthy way to reduce the use of chemical fertilizers and improve plant resistance in rice fields. Azotobacter has been used as a biofertilizer for over a century and has been well studied on a laboratory and field scale. Azotobacter have also been reported as nitrogen-fixing bacteria in the rhizosphere and roots (endophytically) of rice. In this study, the effect of Azotobacter biofertilizer as a plant growth-promoting rhizobacteria, on rice and the mechanisms of this effect were investigated. The results showed that this bacterium produces phytohormones and stimulants of plant growth and fix atmospheric nitrogen in the rhizosphere and as an endophyte in rice. In addition to nitrogen fixation, this bacterium increases plant growth indices, nutrient uptake, and grain yield of rice by dissolving insoluble phosphates, producing indole acetic acid, hydrogen cyanide, siderophore. Also, the use of Azotobacter inoculant in acute salinity conditions increased the concentration of proline, malondialdehyde, ACC-deaminase enzyme, and some hormones in the plant, which increased the resistance of rice to this stress. Considering the positive effect of using Azotobacter inoculant as a biofertilizer on rice plants and the effect of this bacterium on reducing the consumption of nitrogen fertilizers, preparation of biofertilizers containing native bacteria of Azotobacter and their application in rice fields is recommended.