Effects of Different Nitrogen Application Rates on Tobacco Leaf Quality and Nitrogen Use Efficiency of Xiangyan 7 at Different Altitudes

Field experiments were conducted at 300 m, 600 m and 900 m altitudes in Zhangjiajie, and four nitrogen application rates of 120 kg/hm² (N₁), 135 kg/hm² (N₂), 150 kg/hm² (N₃) and 165 kg/hm² (N₄) were set, with no fertilization treatment (N₀) as the blank control. The impact of different nitrogen application rates on the agronomic traits, economic traits, quality of cured leaves and nitrogen use efficiency of Xiangyan 7 tobacco was explored at the three altitudes. The results showed that, the agronomic traits and dry matter accumulation, yield and output value of tobacco plants generally increased with the increase of nitrogen application rate under N₁~N₄ treatments. There was no significant difference in appearance quality. The sensory quality decreased with the increase of nitrogen application rate. The treatments of N₂~N₃ had better chemical composition coordination in all three altitude regions. In conclusion, the suitable nitrogen application rate for Xiangyan 7 in Zhangjiajie tobacco region can be 135~150 kg/hm².