Purpose <p>This study investigates the agricultural application of coal gangue fertilizer through field experiments on summer maize under organic substitution practices. The goal is to enhance coal gangue utilization by evaluating its effects on crop growth and soil nitrogen (N) dynamics.</p> Methods <p>With a consistent N application rate of 240&#xa0;kg ha^− 1, treatments were set with coal gangue and chemical fertilizer proportions of 0% (F1), 25% (F2), 50% (F3), 75% (F4), and 100% (F5), alongside a control treatment (CK) with no fertilizer. The effects of gangue fertilizer on soil N distribution, nitrate N transport, maize growth responses, and N utilization during the reproductive period were studied.</p> Conclusion <p>(1) The application of an appropriate proportion of coal gangue fertilizer increased soil N content in the 0–60&#xa0;cm soil layer during the middle and late stages of maize growth while reducing nitrate N leaching into deeper soil layers. (2) The partial substitution (25%) of chemical fertilizer with coal gangue fertilizer positively influenced dry matter accumulation and N uptake in maize, promoting nutrient transport to kernels. (3) A reasonable proportion of coal gangue fertilizer improved maize yield and N agronomic efficiency. Over two years, the F2 treatment increased yield by 97.6% compared to CK and by 10.0% compared to F1. Nitrogen agronomic efficiency under F2 improved by 22.6% compared to F1, with no significant difference in N fertilizer bias productivity. In summary, substituting 25% of chemical fertilizer with coal gangue fertilizer under equal total N application enhances soil N content in the 0–60&#xa0;cm layer, reduces nitrate leaching, promotes maize dry matter accumulation, delays aging, improves kernel-filling quality, and achieves stable and increased yields.</p> Graphical Abstract <p></p>