Abstract: A field experiment was conducted to study the effects planting density, leaf number and reducing nitrogen on flue-cured tobacco economic characters, physical characteristics and chemical composition. The results showed that applying nitrogen fertilizer at 60 kg/hm2 under high density and low leaf number could increase the output value (013%) by a small margin, but significantly improve the proportion of superior tobacco (11.62%) and the average price (2.38 yuan/kg). In medium density and medium leaf number applying 75 kg/hm2 nitrogen fertilizer could significantly increase the leaf length, leaf width, leaf open degree, and single leaf weight, while there was no significant change in stem ratio. Under high density and low leaf number, applying 60 kg/hm2 nitrogen fertilizer could make no remarkable differences between leaf length, width and open degree and low density and high leave number, but the stem ratio was significantly lower than that of low density and high leaf number. Therefore, the physical properties of both treatments were superior to that of low density and high leaf number treatment. Under these 3 production structures, reducing nitrogen fertilizer application by 15 kg/hm2 could significantly improve chemical components coordination. Under high density (19 500 plants/hm2）and low leaf number(15 piece/plant) applying 60 kg/hm2 nitrogen fertilizer could improve the comprehensive score by 4.59. Therefore, in high nitrogen soil, increasing planting density, reducing leaf number per plant coordinately with reducing nitrogen fertilizer could increase tobacco production value, fine tobacco ratio and average price, and also improve the coordination of tobacco chemical composition. These results have provided new idea for the optimization of flue-cured tobacco grade structure.

Key words: flue cured tobacco, density, leaf number, reducing nitrogen application, economic character, physical index, chemical components

摘要： 采用大田试验的方法研究了种植密度、留叶数与减量施氮对烤烟经济性状、物理特性和化学成分的影响。结果表明，在高密度低留叶数下施60 kg/hm2氮肥，小幅提高了产值(0.13%)，显著提高了上等烟比例(11.62%)和均价(2.38元/kg)。中密度中留叶数下施75 kg/hm2氮肥显著增加了叶长、叶宽、开片度、单叶重，而含梗率并无显著变化，高密度低留叶数下施60 kg/hm2氮肥的处理叶长、叶宽、开片度均与低密度高留叶数无显著差异，但含梗率显著低于低密度高留叶数，因此两者的物理特性均优于低密度高留叶数处理。在3种产量构成条件下，氮肥减量15 kg/hm2可明显提高化学成分协调性，其中高密度低留叶数（19 500株/hm2，留叶数15片/株）配合施氮60 kg/hm2可提高综合得分4.59分。因此在氮素背景较高的土壤上，采取提高种植密度减少单株留叶数配合减少氮肥用量可提高烤烟产值、上等烟比例和均价，并可改善烟叶化学成分协调性。研究结果为当前烤烟等级结构优化提供了新思路。

关键词: 烤烟, 密度, 留叶数, 减量施氮, 经济性状, 物理指标, 化学成分