Studies On The Technologies And Their Effects Of Good Quality And Hight Yield In Guangchang Sun-cured Tobacco

The Guangchang sun-cured tobacco Heilao Tobacco is one of the most famous dark sun-cured totacco in China. Their leaves are of the top quality. Sun-cured tobacco has a very long planting history in China, and many traditional cultivation methods have been developed. However, sun-cured tobacco has not received enough attention because the main ingredient in cigarettes is flue-cured tobacco leaves nowadays. Lack of research resulted in the recession of the existing tobacco varieties, slow development of relevant technologies, and thus the decrease of the quality of tobacoo leaves. In order to meet the demand of“low tar” cigarette production, studies have been done to investigate those problems. Main results are shown as follows:1. Local sun-cured tobacco varieties were collected from 4 villages and towns in Guangchang County. They are Yiqian, Chishui, Toupo and Yangxi sun-cured tobacco. They belong to Tiechi, Mushao, and Liuye tobacco type respectively. They are all good sun-cured tobacco varieties, and each has their own characteristics.2. It is found that the floating-seedling system has obvious adantages compared to the regular seedling system. The seedlings from floating system have better quality and higher resistance, and finally resulted in higher yield, better quality and more assortive chemical composition.3. With plastic mulching, increase in N application level(180 kg/ hm2?210 kg/ hm2?240 kg/ hm2 ? 270 kg/ hm2) resulted in higher yield and higher production value. No significant differences were found in the ratio of the middle-to-high quality tobacco and average price. However, the highest N application rate(270 kg/ hm2) resulted the chorophyll level in leaves became too high, thus adversely affected the maturing of the tobacco leaves and the color-changing during the drying process, and finally adversely affected the quality of the tobacco leaves.4. Studies of different levels of N and P application rates indicated that with low fertility soil, apply no N or P would adversely affect the growth of the tobacco plants and the final yield and quality. If none of N, P and K were applied, the plants could not grow and mature normally. In order to make sure the tobacco plants can growth and mature normally, and obtain high yield and quality, it is very important to apply N, P and K fertilizer to the plants during the cultivation.5. After comparing the 3 topping methods- topping on early button period, toppling at squaring stage, and topping at initial flowering stage- it is found that traditional topping onearly button period could increase the chance for the tobacco plants to get bacterial wilt.Topping at initial flowering stage would cause more nutrients accumulate in the reproductive organs, thus decrease the nicotine, carbohydrate and reducing sugar content in upper leaves. So the best topping method is to topping at squaring stage.6. Studies of havesting at different maturity levels of upper and middle leaves indicated that the tobacco leaves yield decreased with increased maturity, the average price increased with increased maturity; with increased maturity, the total N, nicotine and K content increased, but the pigment content decreased; the change of total carbohydrate differed in middle and upper leaves, in upper leaves, BM3>BM2>BM1; and in middle leaves, BM2>BM3>BM1.7. Among the 4 harvesting methods(T1: Harvesting lower leaves 5-8 days in advance,harvesting order is lower and upper leaves first, and then middle leaves; T2: Harvesting lower and upper leaves together, harvesting order is upper and lower leaves first, and then middle leaves; T3: Harvesting lower and middle leaves together, harvesting oder is upper leaves first, and then middle and lower leaves; T4: regular harvesting method, harvesting order is upper leaves first, middle leaves second and lower leaves finally), yield and production value of T3 are the highest, which were significantly higher than those of T1 and T3; and those of T4 are in the middle. The total carbohydrate and reducing sugar content of T1 are the highest(upper and middle leaves), which indicated that havesting lower leaves early would help to improve the carbohydrate content in middle and upper leaves. The longer the lower leaves stays in the field, the lower its K content.8. Among the 4 drying methods(T1: regular air-cure; T2: air-cure and then sun-cure;T3: sun-cure and then air-cure; T4: smoke drying), T2 and T4 could shorten the drying time; T1 could help to decrease the content of TSNA which is bad for the health, thus improve the quality of the tobacco leaves; consider the production value in addition, T3 and T4 would be better drying methods than the other two.