Effects of Topping Stages on Agronomic Characters,Leaf Yield and Quality of Flue-cured Tobacco Variety NC297

[Objective] The research aimed to study the effects of different topping stages on the Agronomic Characters,leaf yield and quality of flue-cured tobacco NC297.[Method] Field experiment was used.[Result] The results showed that the plant height and the length of internodes of the variety were increased gradually with the postponed topping stage,while the girth growth was first increased and then decreased.The size of upper,middle and lower leaves was affected slightly by topping stage.Topping at budding stage and topping at full blooming stage were both adversely affected the appearance quality of tobacco leaves.The average price,the rate of high class leaf were increased gradually with the postponed topping stage,while the yield was decreased,the yield index and the rate of middle class leaf was first increased and then decreased.The chemical components were harmonious when topping at the early blooming stage.[Conclusion] The study indicates that ftopping at the early blooming stage was the best time for the tobacco variety NC297.