Objectives Yields, nitrogen use efficiency and nitrogen balance have been effective ways in evaluation of nitrogen fertilization. The proper annual amount and allocating ratio of nitrogen fertilizer in wheat and maize were studied in this paper.
Methods Wheat cultivar of Xinmai21 (X21) and Wanmai20 (W20) were used as the material, a three-year located split-block experiment was conducted in the wheat–maize rotation system, Henan Province. Three annual rates of nitrogen application were applied as 300, 450 and 600 kg/hm2, three nitrogen distribution proportions in wheat and maize were applied as 4∶6 (B4), 5∶5 (B5) and 6∶4 (B6). The wheat yield, nitrogen use efficiency and nitrate accumulation in 0–100 cm soil were investigated.
Results The nitrogen fertilizer application rate and proportion had significant effect on yields and their components. For wheat cultivar X21, the treatments of N450 in ratio 5∶5 and 6∶4 and treatment of N600 in ratio 4∶6 all produced satisfactory yields. For wheat cultivar W20, satisfactory yields were obtained in annual nitrogen rates of N450 in both ratio of 5∶5 and 6∶4. The annual total yield was the highest under the N600 in ratio 4∶6, there was no significant difference between N450 in ratio 4∶6, N450 in ratio 5∶5 and N600 in ratio 4∶6. The path analysis suggested that spike was the main factor in X21 yield, while the kernel number was the main factor in W20 yield. The optimum nitrogen use efficiency of X21 and W20 were N450 kg/hm2 in ratio 5∶5 and N600 in ratio 4∶6, respectively. The nitrate accumulation of 0–100 cm soil depth was not obvious in N450 in ratio 5∶5, and there were nitrate accumulation with different degrees in other treatments except N300.
Conclusions Comprehensive considering the annual yields and fertilizer nitrogen use efficiencies, the reasonable annual application amount is 450 kg/hm2, allocated in ratio of 5∶5 in wheat and maize under the experimental condition.
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