The process of biological nitrogen fixation (BNF) in grasses occurs through diazotrophic bacteria, notably Azospirillum brasilense. However, further studies are needed to determine how much mineral N can be applied without altering the efficiency of BNF to achieve high yields. Therefore, the objective of this study was to investigate the effect of inoculation with Azospirillum brasilense and doses and sources of nitrogen on nutrient concentration, production components, and grain yield of irrigated maize and wheat in the Cerrado region.