Effects Of Transplanting Dates On The Curing Characteristics Of Flue-cured Tobacco

In order to investigate the effects of the curing characteristics of flue-cured tobacco in different transplanting periods, a field experiment was conducted from 2014 to 2015 and that with 4 different transplanting dates was tested in Tobacco Planting Areas in Shixing county, Shaoguan city, Guangdong Province, China with the local transplanting dates as a reference, flue-cured tobacco variety K326 as the tested materials. This study was focused on the yellowing characteristics,dehydration characteristics,color fixing characteristics chemical composition at leaf-drying stage in the bulk-curing barn as well as the economic characters of cured tobacco leaves to investigate the effects of the curing characteristics of flue-cured tobacco and to study the effects of tobacco yield and quality characteristics in different transplanting periods. This paper investigated the effects of different transplanting periods on the curing characteristics,yield and quality of flue-cured tobacco, providing a reference for the optimization and improvement of the bulk-curing processing and enriching the theory of flue-cured tobacco curing technology. The main research conclusions were as follows:As the transplanting to delay, the tobacco height, area of largest leaf and space of tobacco leaf also significantly increased,while the largest weight of fresh leaf reduces gradually.The advanced transplanting(February 13th) tobacco can make full use of climate resources in the local tobacco area,thus the fresh tobacco leaves could grow with rich content and good quality.The results showed that the effect of transplanting date on the baking characteristics of tobacco leaves was very significant. Different transplanting period of tobacco leaf water loss at the early stage of the moisture in the baking process dynamic are less, slow water loss, the middle water loss, the characteristics of the filtration speed. Dehydrating rates of tobacco leaves transplanted in February 13 th and those transplanted in local conventional date(February 20th) in different stages during the curing process were close to respective average of the whole process compared to others. So the tobacco transplanted in February 13 th and those transplanted in local conventional date had better dehydrating balance.The degradation of chlorophyll in tobacco leaves transplanted in February 13th and February 20 th was larger, the degradation rate was faster. So they showed better dehydrating and yellowing characteristics during the curing process.During the curing process, the PPO activity in the tobacco leaves transplanted in February 13 th kept lowest, while delayed transplanting leaves(transplanted in February 27th) was the highest, the browning phenomenon also appeared premature and the resistance to baking was worse. Apart from this, the tobacco leaves transplanted in February 13 th maintained a lower membrane lipid oxidation level with less and slower MDA accumulation. The amylase in the tobacco leaves transplanted in February 13 th has the highest activity in the baking process, promoting a sufficient degradation of starch. Besides, during 72 hours bulk-curing, the tobacco leaves contains a proper amount of total-sugar and reducing sugar, nicotine content increased and the ratio of sugar to nicotine decreased.In terms of economic characters, as the transplanting time delays, the yield of each treatment increased gradually, but the proportion of upper-middle class tobacco leaves was significantly reduced. However, the flue-cured tobacco transplanted in February 13 th possessed the highest average price of tobacco leaves and proportion of the upper class tobacco acquires a maximum economic benefits.Therefore, the tobacco should be transplanted in advance(in February 13th)in tobacco-growing regions of Shixing county and had better curing potential and endurable curing potential resulting in better yield and quality of flue-cured tobacco leaves. The tobacco leaves with delayed transplanting and excessive delayed transplanting both had worst curing properties and leaded to worse economic characters.