不同打顶时期及留叶数对湘烟7号产质量的影响

o optimise the cultivation practices of the new tobacco variety Xiangyan NO.7 in the Chongqing tobacco-growing area, a field experimentwas conducted in a two-factor randomised group design to compare the effects of topping method and number of leaves retained on the production potential of Xiangyan NO.7. The experimental site was located in Yuanyang Village, Luoping Town, Wushan County, and the experiment included 6 treatments six treatments,consisting of different topping period (topping at initial-flower stage, topping atfull flowering stage) and the number of leaves retained (18, 20 and 22 leaves). The results showed that the number of leaves retained had an impact of 3-6 days on the growth period of Xiangyan NO.7, while the topping time had no significant effect; the topping time and the number of leaves retained had a significant effect on the opening of the upper leaves of Xiangyan NO.7; the topping time and the number of leaves retainedhad no significant effect on field disease occurrence of Xiangyan NO.7; the topping time and the number of leaves retainedcould affect the economic traits of XiangyanNO.7, but did not reach a significant difference; the topping time and the number of leaves retained had an effect on the chemical composition of XiangyanNO.7. Overall，our date indicate thattopping at full flowering stage and 18leaves retainedresulted in the highest yield,while topping at full flowering stage and 22 leaves retained resulted in the highest production value.