<p>Enhancing nitrogen use efficiency (NUE) is essential for sustainable wheat production. This study evaluated combined effects of <i>Azotobacter chroococcum</i> W5 inoculation and nitrogen fertilizer application on crop productivity, nutrient uptake, nitrogen assimilation, and NUE indices in two wheat genotypes, HD 2967 (<i>Triticum aestivum</i>) and HI 8759 (<i>Triticum durum</i>), under conservation and conventional tillage systems. Five nitrogen regimes were tested: 50% recommended dose of nitrogen (RDN) (N1), 50% RDN + <i>A. chroococcum</i> W5 (N2), 100% RDN (N3), 100% RDN + <i>A. chroococcum</i> W5 (N4), and no nitrogen (N5). Significant genotype x nitrogen management interactions were observed. The highest grain yields were recorded under N4, reaching 5.70 t ha^-1 for HD 2967 and 5.01 t ha^-1 for HI 8759. Importantly, inoculation with <i>A. chroococcum</i> W5 at 50% RDN (N2) resulted in a significant increase in grain yield and macronutrient uptake compared to 100% RDN alone (N3) under both tillage systems. Under conservation tillage, N2 improved grain yield by 78.6% in HD 2967 and 41.3% in HI 8759 compared to N1. Enhanced nitrogen assimilation, particularly increased nitrate reductase activity, together with significantly higher nitrogen uptake efficiency and nitrogen recovery efficiency, were observed in the N2 treatment; while nitrogen utilization efficiency responses were genotype-dependent. Principal component analysis indicated close associations among nutrient uptake, yield parameters, nitrogen assimilation enzyme activities, and most NUE indices. These results highlight the potential of <i>A. chroococcum</i> W5 as a bioinoculant for improving nitrogen efficiency and sustaining wheat productivity under reduced nitrogen inputs, contributing to environmentally sustainable wheat production systems.</p> Graphical Abstract <p></p>