Abstract:

In order to optimize the cultivation techniques of ‘Yunyan 116’ in Shuangjiang tobacco area of Yunnan Province, the problems of difficult yellowing in maturity, heavy green and mixed gas, and uncoordinated chemical composition were studied. Using ‘Yunyan 116’ as the test material, nine treatments were set up according to L₉(3⁴), with nitrogen application rates of 99, 111 and 123 kg/hm²; planting densities of 1200 mm×500 mm, 1100 mm×500 mm and 1000 mm×500 mm; topping periods of present bud topping, early flowering topping and full flowering topping; and the number of leaves retained were 18, 20 and 22, respectively. The results showed that plant height, stem circumference and pitch increased with the increase of nitrogen application; plant height decreased with the increase of planting density; maximum leaf length and width increased with the advance of topping period; and maximum leaf length increased with the decrease of the number of leaves retained. In terms of agronomic traits and comprehensive quality of flue-cured tobacco, nitrogen application had a greater effect on plant height, pitch, maximum leaf length, manganese, total nitrogen, starch, protein, and comprehensive score of sensory quality; planting density had a greater effect on boron, silica, total sugar, reducing sugar, total phytochemical alkaloid, potassium oxide, chlorine, and aroma-causing constituents such as ciprofloxacin-like, meladic reaction products, phenylalanine, and chlorophyll; and topping period had a greater effect on stem circumference and maximum leaf width; and the maximum leaf width increased with the advancement of topping period; and the maximum leaf length increased with the decrease of the number of retained leaves. The topping period significantly influences stem circumference and maximum leaf width, and has a more pronounced effect on zinc, iron, and carotenoid degradation products within the aroma components of tobacco leaves. Meanwhile, the number of leaves retained after topping exerts a greater influence on the calcium, magnesium, and copper elements in tobacco leaves. On the whole, nitrogen application rates of 111 kg/hm² can be used in conjunction with bud topping and 20 retained leaves, which can promote leaf maturity through the regulation of carbon and nitrogen metabolism. In the future work of flue-cured tobacco production in Shuangjiang County, when pursuing the aroma style, high nitrogen (123 kg/hm²), sparse planting (1200 mm×500 mm), early bud topping, and leaving 20 leaves can be adopted, and when pursuing the sensory coordination of tobacco, medium nitrogen (111 kg/hm²), dense planting (1000 mm×500 mm), and 18 retained leaves can be adopted.

Key words: cultivation measures, Shuangjiang, Yunnan, ‘Yunyan 116’, agronomic traits, medium and trace elements, chemical composition, sensory quality, aroma-forming components