Abstract: The replacement of chemical fertilizers with organic fertilizers is an important technical measure for achieving fertilizer reduction and efficiency and for controlling soil pollution. In this study, we aimed to investigate the responses of maize yield, maize nitrogen uptake and use efficiency, and soil nitrogen leaching to different substituion ratios of chemical fertilizer with organic fertilizer. The main objective was to provide a scientific basis for the efficient use of maize nitrogen resources and for the prevention and control of agricultural non-point source pollution in the Yellow River Water Irrigation Area of Ningxia. To this end, we conducted field experiments in 2022 and 2023 at the National Meteorological Station of Yongning County, Ningxia. A completely randomized block experimental design was adopted based on the local conventional nitrogen application rate of 270 kg·hm⁻². The fertilization treatments were as follows: 100% chemical fertilizer treatment (T1), 2/3 chemical fertilizer + 1/3 organic fertilizer treatment (T2), 1/3 chemical fertilizer + 2/3 organic fertilizer treatment (T3), 100% organic fertilizer treatment (T4), and the control treatment without fertilizer (CK). Soil nitrogen loss, maize yield, nitrogen uptake, nitrogen transport, and nitrogen use efficiency were analyzed. The results showed that maize yield and aboveground nitrogen uptake at maturity stage under T2 treatment were the highest. Based on 2-year average, maize yield under T2 treatment increased by 73.42% compared to that under CK treatment, while it increased by 3.67% compared to that under T1 treatment; aboveground nitrogen uptake at maturity stage under T2 treatment incrased by 97.09% compared to that under CK treatment, and it increased by 9.98% compared to that under T1 treatment. Additionally, translocation amount, translocation rate, contribution rate to grain nitrogen of nitrogen accumulated in vegetative organs pre-flowering, as well as nitrogen assimilation after anthesis under T2 treatment increased by 171.18%, 19.67%, 36.89%, and 72.17% compared to that under CK treatment, respectively, and 24.36%, 6.74%, 12.94%, and 3.55% compared to that under T1 treatment, respectively. The mean values of apparent recovery efficiency of nitrogen, agronomic use efficiency of nitrogen fertilizer, and partial factor productivity of nitrogen fertilizer under T2 treatment increased by 22.58%, 9.17%, and 3.67%, respectively, comopared to that under T1 treatment. However, there was no significant difference in nitrogen harvest index among different treatments in 2022 and 2023. In addition, the total nitrogen, nitrate nitrogen, and ammonium nitrogen concentrations in the leachate under T2 treatment were relatively low. The total nitrogen, nitrate nitrogen, and ammonium nitrogen leaching losses under T2 treatment decreased by 24.56%, 25.29%, and 23.70% compared to T1 treatment, respectively, and corresponding leaching coefficients decreased by 37.95%, 39.44%, and 26.83%, respectively. Indicators of maize nitrogen uptake, translocation, and utilization showed a significant positive correlation with maize yield. In the regression curves of maize yield versus organic fertilizer substitution ratio, maize yield with organic fertilizer substitution ratio at 36.53% was the highest, nitrogen uptake, translocation, and nitrogen use efficiency were also high, while nitrogen leaching was low. Therefore, the optimal organic fertilizer substitution ratio for maize production in the Yellow River Water Irrigation Area of Ningxia is 36.53% (98.64 kg·hm⁻² organic fertilizer replacing chemical fertilizer), which supports the higher nitrogen use efficiency for maize and reduces agricultural non-point source pollution.