Effect of Nitrogen Application Rate and Planting Density on Growth, Photosynthetic Characteristics, Yield and Quality of Flue-cured Tobacco

Yunyan 87 cultivar was used as the experimental object, and a two-factor randomized block trial design including three Nitrogen application levels（N₁: 127.5 kg/hm², N₂: 142.5 kg/hm², N₃: 157.5 kg/hm²） and three planting densities（M₁: 15000 plants/hm², M₂: 16500 plants/hm², M₃: 18000 plants/hm²） were conducted to explore the effects of nitrogen application rate and plant density on the growth characteristics, total dry matter accumulation, photosynthetic characteristics, economic traits, sensory quality characteristics of tobacco leaves. The result showed that under the same nitrogen conditions, with the increase of planting density, the stem circumference and dry matter accumulation of flue-cured tobacco plants decreased, the net photosynthetic rate and stomatal conductance showed a decreasing trend, the yield and output value of flue-cured tobacco increased but the average price decreased, the total sugar content of flue-cured tobacco leaves increased, the contents of nicotine and total nitrogen decreased, and the sensory quality showed a downward trend. Under the same planting density, with the increase of nitrogen fertilizer application, the growth and development of tobacco promoted significantly, the accumulation of dry matter and photosynthesis of tobacco leaves increased, the yield and output value increased significantly, the nicotine and total nitrogen content of tobacco leaves increased significantly, the sensory quality of tobacco leaves treated with medium to low density treatment showed an initial increase followed by a decrease, while the sensory quality of tobacco leaves with high density treatment decreased. Considering the economic benefits and quality, the medium density and medium nitrogen（N₂M₂） treatment showed excellent agronomic traits in tobacco leaves, with the highest dry matter accumulation, the best economic benefits, good coordination of internal chemical components, and the best sensory evaluation of smoking quality, which could be recommended as a high-quality tobacco planting plan in Ganzhou tobacco-growing area.