This study was conducted in split plots in a RCBD design with 3 replications at Ferdowsi University of Mashhad. Main plot factor included: irrigation levels (100, 75, 50 and 25% of water requirement), and subplot factor included: fertilizer levels (Nitroxin®; containing Azotobacter and Azospirillum bacteria, Biophosphorus®; containing Pseudomonas and Bacillus bacteria, Nitrogen chemical fertilizer (Urea), and control (no fertilizer). Biological fertilizer treatments were applied as seed inoculation before cultivation. Based on results, the application of growth-promoting bacteria under stress conditions led to an increase in grain yield of corn compare to control treatment, significantly. The highest grain yield of corn under water stress conditions in the combined treatment (Nitroxin fertilizer and 25% water requirement) with 6223.3 kg of grain per hectare compared to the control (2236.7 kg of grain per hectare). Overall, the results of this study showed that the ability of Azotobacter and Azospirillum in the nitrogen fixation process and the ability of Pseudomonas and Bacillus in dissolving insoluble phosphates effectively increased the yield of corn grain. As a result, the use of biological fertilizers has a beneficial and effective role in grain yield of corn plants.

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