Effects of different threshing patterns on weight per leaf, yield and quality of flue-cured tobacco

Objective Effects of removing bottom and upper leaves on weight per leaf of leaves at different positions and tobacco quality were studied to offer a basis for formulating fresh tobacco leaf treatment measures in field,optimizing tobacco structure and improving tobacco quality.Method A field experiment was carried out using tobacco variety Yunyah97.There were three treatments.Treatment 1 (T1,CK):removed the orignal leaves at the bottom of stick at resettling stage(about 40 d after transplant),and removed the flower branches and extra leaves on it at squaring stage when the first center flower bloomed (about 60 d after transplant),maintaining 18 leaves per plant.Treatment 2 (T2):on the basis of T1,removed two more leaves at the bottom of the tobacco plant at topping stage and maintained 16 leaves per plant.Treatment 3 (T3):on the basis of T2,removed two more leaves at the top of the tobacco plant 20 d after topping,and maintained 14 leaves per plant.The leaves at different positions of tested plants were labeled.According to production standards,the leaves of the tested plants were harvested and cured,and every leaves were graded and weighted one by one,then weight per leaf,yield,output value,average price,grade structure and other indicators were calculated.Result As the number of leaves remained decreased,both the average fresh weight per leaf and average dry weight per leaf increased and presented T 1 T2(2734.5 kg/ha)>T3 (2583.0 kg/ha).In T2,first-and-second-class rate(90.18%) and production value(61493.1 yuan/ha) were the highest,but it was not significantly different from those of T1 (P>0.05).But the values of T1 and T2 were significantly higher than those of T3.Conclusion Removing two more bottom leaves at topping stage can moderately increase weight per leaf,improve first-and second-class rate and average price,and the yield loss of tobacco leaves is smallwith high output value.But removing extra two leaves at top part 20 d after topping causes weight per leaf of middle and upper leaves to exceed standard,quality grade to decline,yield and output value to lose greatly,It is suggested that removing two extra bottom leaves to be removed at topping stage in field.But whether removing two more top leaves later or not should be judged according to the growth and nutrition status of tobacco plants.