Abstract:

To select a reasonable nitrogen application rate for ‘Hongda’ flue-cured tobacco in Baoshan tobacco-growing area, field experiments were conducted to study the effects of different nitrogen application rates on the growth and development of roots, agronomic traits, economic traits and leaf quality of flue-cured tobacco. The results showed that the maximum leaf width and maximum leaf length of 75 kg/hm² and 90 kg/hm² N treatments were significantly higher than those of other treatments, which increased by 21.92% and 18.83%, respectively, compared with those of 45 kg/hm² N treatment. The total root length, mean root diameter, total root volume, root apical count and root bifurcation count under N treatment of 75 kg/hm² and 90 kg/hm² were significantly higher than those under N treatment of 45 kg/hm² and 60 kg/hm² at budding stage and after topping. The growth rate of root length was the highest from the growing stage to the budding stage, while the growth rate of root diameter, surface area and total volume were the highest from the resettling growth stage to the vigorous growth stage. The content of total nitrogen and nicotine in the upper tobacco leaves were higher after curing, and the sensory quality of tobacco leaves decreased with the increase of nitrogen application amount. Overall, the comprehensive evaluation of appearance quality and chemical composition coordination of tobacco under nitrogen application rate of 75 kg/hm² were relatively good, and the comprehensive evaluation of physical properties and sensory quality of tobacco under nitrogen application rate of 45 kg/hm² were relatively excellent. Considering the growth of flue-cured tobacco and the quality of tobacco leaves, 75 kg/hm² nitrogen application rate is recommended for ‘Hongda’ in Baoshan tobacco area.

Key words: Baoshan, ‘Hongda’, nitrogen level, root morphology, tobacco leaf quality