In order to study the effects of nitrogen and plant growth promoting rhizobacteria (PGPR) on yield and some growth indices of sunflower (Helianthus annus L.), a factorial experiment was conducted based on randomized complete block design with three replications. Factors were: nitrogen fertilizer in three levels (0, 80 and 160 kg N ha-1) from urea as N0, N80 and N160 respectively and seed inoculation with plant growth promoting rhizobacteria in four levels containing, without inoculation (as

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... rol), seed inoculation with Azotobacter chroococcum strain 5, Azospirillum lipoferum strain of, Psedomunas putida strain 186. Results indicated that quantitative and qualitative yield increased with increasing of nitrogen fertilizer and application of PGPR. Means comparison showed that N160×without inoculation with PGPR and N80×seed inoculation with Azotobacter had similar grain yields. Seed inoculation with Azotobacter increased leaf area index and total dry matter. In all of treatment compounds, leaf area index and total dry matter increased slowly until 45 days after sowing. From 45 days after sowing till 95 days after sowing increased rapidly.Then till 115 days after sowing, it decreased due to increasing aging of leaves, shading and competition for light and the other resources. So, it seems that in order to increasing of grain yield and growth indices, it can be suggested that be applied 80 kg N/ha × seed inoculation with Azotobacter.