The effect of dual microorganisms inoculation on the amount of plant growth regulator and barley grain yield under different nitrogen levels

In order to investigate the effect of dual phosphorus and Azospirilum solubilizing bacteria on hormonal condition and barley grain yield under different levels of nitrogen, an experiment was conducted in Agricultural Research Station of Islamic Azad University of Karaj, in 2014. The experiment was based on a factorial split plot design in a randomized complete block design with three replications. The treatments included the main factor of the Nitrogen fertilizer in four levels (0, 50, 75 and 100%, equivalent to zero, 150, 225 and 300 kg per Hectares respectively) and sub factors including Azospirilum lipophorm bacteria in two levels (application and non-application of bacteria) and Pseudomonas fluorescens bacterium in two levels (application and non-application of bacteria). The results showed that application of 75% nitrogen and A. lipophorum and the application of the main treatment of P. fluorescens produced the highest amount of auxin hormone. The interactions of urea and A. lipophorum and the dual interactions of A. lipophorum and P. fluorescens produced the highest levels of cytokinin hormone. The levels of hormones showed in the triple treatments of 100% nitrogen, A. lipophorum and P. fluorescens bacteria compared to control treatment (not treatments) had 261.1% difference. The highest grain yield were observed in p. fluorescens (4700 kg ha-1) treatment and using 100% application of urea and A. lipophorum (5500 kg ha-1). As a result, the application of nitrogen fertilizer and the use of both types of biological fertilizers led to an increase in the production of hormones that increased root growth, ultimately, increased water absorption and nutrients from the soil and increased grain yield.