effects of plant growth promoting rhizobacteria and nitrogen fertilizer on yield and yield components of maize

to evaluate the effects of plant growth promoting rhizobacteria (pgpr) such as azotobacter chroococcum, azospirillum lipoferom and brasilence and pseudomonas fluorescens and nitrogen fertilizer from urea source on yield and yield components of maize (zea mays l.) double cross hybrids (dc 370), a field experiment was carried out in a factorial experiment (5*3) in rcbd with 4 replications. bacterial were treated at 5 levels including, b0= no inoculation (control), b1= azotobacter + azospirillum, b2= azospirillum+ pseudomonas, b3= azotobacter + pseudomonas and b4= azotobacter + azospirillum + pseudomonas and urea fertilizer with zero (control), 100 and 200 kg/ha as the nitrogen treatments. the results showed that the highest increase traits in plants growth promoting rhizobacteria related to azotobacter + pseudomonas treatment that increased grain yield, biological yield, number of rows per ear, cob yield and cob yield per plant by 23.8%, 22.7%, 6.2%, 26.9% and 19.8%, respectively. nitrogen fertilizer related to 200 kg/ha urea increased grain yield, biological yield and thousand kernel weight by 17.8%, 18.7% and 3.2%, respectively. the interaction of bacteria and nitrogen fertilizer treatments was detected. azotobacter + pseudomonas treatment had the most effect on most of these traits necessarily in the presence of 200 kg/ha urea, but the combined use of azotobacter, azospirillum and pseudomonas increased these traits without needing urea and application of urea caused decrease proficiency of this rhizobacteria.