Objective The aims were to explore the effect of nitrogen fertilizer combined with biochar on maize material production and nitrogen efficiency, and to provide reference for high yield and high efficiency cultivation of maize.

Method A split-zone design was used, with nitrogen application as the main zone with three levels of 0, 150, and 300 kg hm⁻² (denoted by N₀, N₁₅₀, and N₃₀₀, respectively), and biochar application as the sub-zone with four levels of 0, 8, 16, and 24 t hm⁻² (denoted by C₀, C₈, C₁₆, and C₂₄, respectively). The effects of nitrogen fertilizer with biochar on dry matter accumulation and translocation, nitrogen accumulation and translocation and nitrogen efficiency of maize were investigated.

Result The results showed that the dry matter accumulation and translocation of maize at the N₀ level were significantly higher in C₈ than in the other treatments. The dry matter accumulation of C₈ was 3.72% higher than that of C₀ at silking stage and 5.49% higher than that of C₀ at maturity stage. At the N₁₅₀ level of dry matter accumulation, C₁₆ was 4.34% higher than C₀ at the silking stage and 7.74% higher at the maturity stage. The dry matter translocation of C₁₆ was 20.78% higher than that of C₀ at N₁₅₀ level, and 16.79% higher at N₃₀₀ level. The contribution rate of dry matter transport to grain was not significantly different between treatments at N₀ level, C₁₆ was 6.55% higher than C₀ at N₁₅₀ level which was significant, and there was no significant difference among treatments at N₃₀₀ level. Nitrogen fertilizer combined with biochar promoted the nitrogen accumulation and translocation of maize. Nitrogen accumulation was the highest in C₈ at the silking stage at the N₀ level, and C₁₆ was the highest at the N₁₅₀ and N₃₀₀ levels. The highest was C₁₆ at N₁₅₀ and N₃₀₀ levels at the maturity stage. Nitrogen translocation was the highest in C₈ at N₀ level, and C₁₆ was the highest at N₁₅₀ and N₃₀₀ levels. Nitrogen fertilizer combined with biochar further increased maize grain yield. The C₈ was the highest at the N₀ level, which was 9.93% ~ 12.68% higher than C₀, and C₁₆ was the highest at N₁₅₀ with 13.35% ~ 13.98% higher than C₀, and was the highest at N₃₀₀ with 13.05% ~ 15.18%. Correlation analysis showed that there was a significant positive correlation between nitrogen application, maize material accumulation, nitrogen accumulation and nitrogen fertilizer contribution rate. There was a positive correlation between carbon application, maize nitrogen accumulation, nitrogen fertilizer agronomic efficiency, nitrogen fertilizer partial productivity, nitrogen fertilizer absorption efficiency, nitrogen utilization efficiency and nitrogen fertilizer contribution rate.

Conclusion Nitrogen application rate of 300 kg hm⁻² combined with biochar application rate of 16 t hm⁻² could improve maize grain yield and nitrogen efficiency, which is suitable amount of nitrogen and biochar for high yield and high efficiency cultivation of maize in the Xiliaohe Plain.