Study On The Relationship Between Field Growth Time And Quality Of Flue-Cured Tobacco And Its Control Technique

Tobacco is the important economic crop in Yunnan province, and its unique style of fen-flavor renowned at home and abroad. But the problem that the field growth time is insufficiency and the maturity is not enough is outstanding in tobacco production. Aiming at this problem, this study lasted two years. In order to provide theoretical support for the suitable field growth time and the cultivation techniques which guarantee the suitable field growth time of flue-cured tobacco, including the study on the relationship between field growth time and quality of tobacco、the mechanism of field growth time effect on quality formation of tobacco、field growth time and its restraint factors of tobacco in different ecological areas and the cultivation techniques which guarantee the suitable field growth time of tobacco has been done in Yunnan production areas. The main results are as followings:1. Define the relationship between field growth time and quality of tobaccoIn Yuxi, we carried out field trials in 2012. We set up three treatments including normal harvest、later 7 and 14 days than the normal harvest. From the impact of field growth time on the tobacco production output, we can see the yield、production value、ratio of the classy and the average price of tobacco are gradually reduced when the harvest time was delayed, and the ratio of medium was rising first and then falling. From the impact on the chemical quality, we can see the starch content is low when the harvest time of middle leaf was delayed by 7 days. The chemical components are in the suitable range and the coordination is better when the harvest time of middle leaf was delayed by 7 days. The nicotine content、the ratio of total nitrogen and nicotine、the ratio of total sugar and nicotine are appropriate when the harvest time of the upper leaf was delayed by 7 days, but its starch content is higher than the normal range. From the impact on the sensory quality and style characteristic, we can see the overall quality features is best which harvested 7 days later than the normal, and followed by the leaves which harvested 14 days later than the normal. The main flavor was same between different treatments. The total style characteristic is best when the harvest time was delayed by 7 days, and its characteristic of fen-flavor is obvious. Second is the treatment which the harvest time was delayed by 14 days. Therefore, we can preliminary define that the middle leaf was appropriately harvested between normal time and 7 days later than normal and the upper leaf was appropriately harvested between 7 days and 14 days later than normal.2. Study the basis of substance metabolism of the field growth time affect the tobacco quality(1) Along with the extension of filed growth time, total nitrogen content、the ratio of sugar and nicotine、the ratio of total nitrogen and nicotine were gradually reduced, and the nicotine content was rising first and then falling. Except the rapidly changes of total sugar content before and after topping, the total sugar content of middle and upper leaf is highest when the harvest time was delayed by 7 days. The glucose content is highest when the middle leaf was harvested at normal time and the upper leaf was harvested at 7 days later than normal. The SPS activity of middle and upper leaf is highest when leaves were harvested at normal time. SS activity of middle and upper leaf presented single-peak curve, and after that the SS activity reduced.(2) Along with the extension of filed growth time, chlorogenic acid、scopoletin and rutin content of middle and upper leaf were gradually rising. This study proves that there is a close correlation between the phenolics content and PAL activity in the growth process of flue-cured tobacco. In addition to the scopoletin, PAL activity and phenolics content are positively correlated, and reached 1% significant level. PPO activity and phenolics content are negatively correlated, and the correlation between PPO activity and chlorogenic acid content in middle leaf reached 5% significant level, and the correlation between PPO activity and the total polyphenols、chlorogenic acid and rutin content in the upper leaf reached 1% significant level.(3) Along with the extension of filed growth time, the content of IAA.. the ratio of IAA and ABA reached peak at 93 days after transplanting. The content of CTK、the ratio of CTK and ABA reached peak at 100 days after transplanting. The content of ABA reached peak at normal harvest time. All these gradually reduced after the peak. Changes of the main chemical compositions and its related enzyme activity、phenolics content and its related enzyme activity and endogenous hormone content in the growth process of tobacco is the further evidence that the middle leaf was appropriately harvested between normal time and 7 days later than normal and the upper leaf was appropriately harvested between 7 days and 14 days later than normal.3. Define the key factors affect the field growth time of tobacco in fen-flavor production areasTobacco production information of 21 cities (including 261 towns) in Yunnan, Fujian and some place of Guizhou and Sichuan were analyzed. Found that there is significant difference in field growth time between different ecological regions and the key factors affect field growth time is meteorological factors and cultivation techniques.4. Put forward the cultivation techniques which guarantee the suitable field growth timeThrough the analysis of the above data, we ensure that the range of suitable field growth time of tobacco in fen-flavor production area is 107-140 days. But there is a difference between different parts, the range of suitable field growth time of middle leaf is 107-114 days, and the upper leaf is 133-140 days.Field trials set up three nitrogen application rate including 4、6 and 8Kg per 667 m2 and three planting density including 1100、1282 and 1345 plants per 667 m2.According to the results of economic and physical properties、chemical composition and sensory evaluation, we can determined that the treatment of N-applied 6Kg per 667、when harvested 7 days later than normal and the treatment of 1100 plants per 667m2 when harvested between normal time and 7 days later than normal can guarantee the suitable field growth time of middle leaf. The treatment of N-applied 6Kg per 667m2 when harvested 14 days later than normal and the treatment of 1282 plants per 667、when harvested 7 days later than normal time can guarantee the suitable field growth time of upper leaf.