Effects Of Bagging And No Topping On Growth Of Flue-cured Tobacco And Yield And Quality Of Upper Leaves

Aiming at the problem of low yield and quality of the upper leaves of flue-cured tobacco in China,the bagging experiment was conducted in the experimental field of Hunan Agricultural University in Changsha City,Hunan Province in 2019.Eight treatments were set up in this experiment: T1: Blue bagging in the bud stage;T2: Black bagging in the bud stage;T3: Blue bagging in the early stage of flowering;T4: Black bagging in the early stage of flowering;T5: Blue bagging in the middle stage of flowering;T6: Blue bagging in the early stage of flowering In the middle stage of flowering,black bags are set;T7: no bags,no topping;T8: conventional topping.The effects of topping in different periods on the growth and development of roots,stems and leaves and the industrial availability of upper leaves of flue-cured tobacco were studied by using randomized block design:(1)Effect on the growth of Flue-cured Tobacco:Bagging and no topping can affect the dry matter accumulation of tobacco plants.The dry weight of leaves and the proportion of leaves in the total dry weight of plants were all non topping and non bagging treatment < bagging and non topping treatment < conventional topping treatment,while the dry weight of stems and its proportion in the total dry weight were routine topping treatment < bagging and non topping and non bagging treatment < non topping and non bagging treatment.bagging and no topping can weaken the secondary growth of tobacco roots.After 60-80 days of transplanting,the increase of root volume and the root activity of flue-cured tobacco was as follows: no topping and no bagging treatment < no topping and no bagging treatment< routine topping treatment.There was no significant effect of bagging and no topping on the phosphorus content of tobacco plants,but it could affect the total nitrogen content in leaves and potassium content in roots.From 60 days to 80 days after transplanting,the decrease of total nitrogen content in bagging and no topping treatment was larger than that in conventional topping treatment,which indicated that bagging and no topping treatment could reduce the accumulation of total nitrogen in leaves;from 60 days to 80 days after transplanting,the increase of potassium content in roots was no topping and no bagging treatment<bagging and no topping treatment<conventional topping treatment;from the proportion of potassium content in roots in total potassium content of plants Except for the decrease of no topping and no bagging treatment,the proportion of other treatments increased,and the increase of conventional topping treatment was the largest,which indicated that the bagging and no topping treatment could weaken the potassium backflow to the root.(2)Effect of economic characters of Flue-cured Tobacco:The yield of conventional topping treatment was the highest,followed by the blue bag treatment in bud stage,and the yield of non topping and non bagging treatment was the lowest.The proportion of top-grade and medium-grade and average price tobacco in the blue bag treatment in bud stage was the best,followed by the conventional topping treatment,and non topping and non bagging treatment was the worst.(3)Effect of the availability of upper leaves of Flue-cured Tobacco:Bagging and no topping is beneficial to improve the quality of upper leaves.In the four upper leaves,the nicotine content of conventional topping treatment was significantly higher than that of other treatments,indicating that bagging and non topping could significantly reduce the nicotine content of upper leaves.The content of reducing sugar in the last one leaf and the last three leaves was the highest in the conventional topping treatment.The content of total sugar and reducing sugar in the rest leaves were not significantly higher in the blue bag treatment than in the conventional topping treatment and significantly higher than in the non topping and non bagging treatment.The K / C ratio of the top leaves of all bagging free treatments was significantly higher than that of the conventional topping treatments,which indicated that bagging was beneficial to improve the combustibility of the upper leaves.The sugar alkali ratio of the blue bagging treatment,the black bagging treatment and the blue bagging treatment were significantly higher than that of the conventional topping treatment,and the nitrogen alkali ratio of the non topping treatment was significantly higher than that of the conventional topping treatment,indicating that the bagging was beneficial to the coordination of the chemical components of the upper leaves after baking.The earlier the bagging period is,the better the quality of the upper leaves is.The blue bagging is better than the black bagging.The results showed that the blue bag treatment was the best treatment to improve the quality of the upper leaves.