| In order to decrease the proportion of mottle tobacco and improve the usability of tobacco leaves, different key techniques of high-quality tobacco leaves production in fertilization levels, harvest time and ways of tobacco leaves, bulk curing act were studied in this paper. The results were as follows:1. Tobacco leaves which easily came into being mottle leaves had low water content, compact tissue structure, low polyphenol oxidase activities and pigment content, high starch and nitrogenous compounds contents. Tobacco leaves thickness had a close relationship with mottle. Commonly the suitable standards were not exceeding 155μm for upper leaves, about 130μm for cutters, and about 120μm for lower leaves.2. Improving tobacco field and tobacco leaves nutrition to increase tobacco leaves quality. By methods of scientific and rational fertilization and water regulation, let tobacco fields-tobacco plants-tobacco leaves up to nutrition balance in each growth period. Using 20~40 kg cake fertilizer per mu, flue-cured tobacco leaves had good quality, low proportion of mottle, and high proportion of grade A leaves and better usability of middle grade leaves; the treatment of 50% nitrate nitrogen+50% ammonia nitrogen was the best. If proportion of nitrate nitrogen was too high, cutters and lower leaves were thinner, and upper leaves could not grow naturally; if proportion of ammonia nitrogen was too high, upper leaves were easy to mature late and too thick;Spraying proper micro-element fertilizer on the leaves, tobacco leaves could expand better to improve tissue structure and to reduce the proportion of mottle tobacco. Irrigation fully at fast growing period and irrigate properly at mature period could increase the quality of fresh leaves, and improve the proportion of grade A leaves.3. Appropriate tobacco topping and harvesting methods. When 50% tobacco plants of the total opening the first flower in the fields, began to topping and harvesting at 5~10 days after the topping day, the proportion of grade A leaves could be increased. Cutting and baking the top last 4~6 leaves with stem, flue-cured tobacco had good usability.Compared with the traditional harvest way, harvesting the lower leaves after topping 5~10 days, leaves thickness and leaf area per unit could increase 5%~10%; the proportion of orange tobacco could increase 10%~15%; chemical components were more coordinate; the thickness of upper leaves and leaf area weight could reduce, and the proportion of mottle tobacco reduced, and the proportion of high and medium tobacco grades could increase significantly.The quality of collecting 4~6 upper leaves and cured at one time was better than that of collecting 2~3 upper leaves; collecting 4~6 upper leaves and cured with stem at maturity was the best, which could improve the appearance quality of upper leaves, reduce 5%~10% of mottle tobacco, and increase 10% of the proportion of high and medium grade leaves.4. Mottle leaves were mainly appeared in the lower and the upper leaves, so suitable cured techniques (focusing on several temperature periods) should be taken in order to reduce the occurrence of mottle leaves, and to increase proportion of high quality tobacco. Experiments showed that the lower leaves should turn to yellow at the temperature of 38℃~42℃, and the middle and upper leaves turn to yellow at controlling the temperature around 38℃; after tobacco leaves turning to yellow, tobacco leaves should be fully softened at 41℃~42℃and extended the time of eliminating moisture when the temperature at 48℃~49℃.5. The volume of tobacco aroma of cured leaves for the bulk curing barn was significantly better than that for the ordinary barn, and motley leaves were little or very different to occur. Because the bulk curing barn could make tobacco leaves turn to yellow fully, had a much bigger ventilation speed among leaves, and easily coordinated leaves yellowing and drying.To make a reasonable regulation for tobacco density in the curing course could greatly improve the quality of tobacco. Middle leaves with a density of 55 to 65 kg/m3, yellowing at low temperature and appropriately prolonging the time (After a small part tobacco turning to yellow at 35℃, then warming to 38℃; when leaf yellowing to reach the fire turning point, then prolonging 12 hours for leaf turning yellow) could obtain the optimal transformation for some physiological indexes at the curing process. At the same tobacco density, yellowing leaf at 35℃to 38℃of the dry-bulb temperature with relative humidity 82% could get the best tobacco comprehensive quality.6. Each individual test had the role of improving tobacco quality, and finally reduced 5%~15% mottle tobacco."Rules of tobacco production technology for reducing variegated leaves and increasing the proportion of grade A and usability"were proposed and applied. The proportion of variegated leaves was 6%~12% reduced, and the proportion of high and medium leaves reached more than 85% with a the relative increase of more than 10%. |
