| Xiangxi tobacco growing area is the main tobacco growing areas in Hunan which has yearly yield of250,000kilos. It is good in appearance and quality, coordinated in chemical components, good in compatibility and welcomed by different tobacco manufacturing enterprises. But up to now, studies focusing on ecological conditions, soil conditions and quality of tobacco are relatively rare. Therefore, this study is of significance in clarifying ecological resources which is suitable for Xiangxi tobacco; its features and evaluation of cultivated land resources and soil nutrient status; flue-cured tobacco’s quality features and comprehensive evaluation of the quality and the relation between tobacco leaves quality and ecological factors in Xiangxi tobacco growing area.1. Features and evaluation of climate resources in Xiangxi tobacco growing area.The average temperature of the field growing period in Xiangxi tobacco area is19.76-25.43℃. Though isn’t that high, the average temperature of the mature period is22.13-27.74℃. Higher the temperature is in the later stage, which is good for the accumulation of the assimilation products and the improvement of the quality of the tobacco. The effective accumulated temperature of the field period in Xiangxi when it is above10℃is2631.07～2880.21℃, which is good for the flue-cured tobacco’s field growing period. So the effective accumulated in the field growing period can totally satisfy the growing of the flue-cured tobacco, and it is very suitable for high quality tobacco leaves when coordinate with light, water and soil.The average monthly rainfall of the root-extended period in Xiangxi tobacco area is above100mm. So the individual years of the field tobacco must pay attention to ditch cleaning and water draining, to help promote root growth. When it is the fast growing period the rainfall is so adequate, and the average monthly rainfall is above100mm, along with warm sunshine, suitable temperature, which is benefit for the tobacco producing. But when it is the mature period, the rainfall is too much which is bad for the tobacco harvesting.The sunshine duration of the tobacco’s field growing period in Xiangxi is generally565.92-703.51h. When transplanted to fast growing period it is above250h, and the harvest baking period the sunshine duration is above300h. But the field growing period is during the rainy season, the cloud cover is enough, the percentage of sunshine is about40%, which meets the need of high quality tobacco produce.As a whole, the tobacco area in Xiangxi with rather abundant heat resources and coordinate with superior light, temperature and water condition. The climate condition of the field growing period when compared with the high quality tobacco leaves abroad, existing some problems, that is:relatively lack of sunshine; the comparative low temperature in the early stage; excessively rainfall and too much humidity.An analysis about the degree of similarity on climatic conditions of tobacco growing areas between Xiangxi and producing areas with high quality tobacco at home and abroad, revealed that the similarity of climate condition was the highest between Xiangxi and Zunyi, follwed by Chenzhou and Brizal. Compared with the climate of flue-cured tobacco during different field growing period of other producing areas at home and abroad, in the earlier stage, Xiang Xi is similar to Zunyi and Xuchang; in the middle stage, Xiangxi is similar to Zunyi; and in the later stage, Xiangxi is similar to Zunyi and Xuchang. According to those statement, it can be inferred that, the aromas types of flue-cured tobacco of Xiangxi is between that of Zunyi and that of Xuchang, however, it is the most similar to that of Zunyi. the aromas type of flue-cured tobacco of Zunyi of Guizhou province is intermediate; that of Xuchang in Henan province is typically strong; so it can be concluded tentatively, that of Xiangxi is between intermediate and strong.The daily average temperature of flue-cured tobacco during field growing period in Xiangxi is above20℃; the sunshine duration is more than500h; and the amount of precipitation is over700mm. So Xiangxi possesses the general conditions and advantages to plant flue-cured tobacco with high quality. In Xiangxi, flue-cured tobacco during the earlier field growing period enjoys relatively higher daily average temperature, more rainfall and great air humidity, which are beneficial to the survival of transplantation and early growth and quick tillering. In the intermediate and later field period, those tobacco enjoys relatively higher daily average temperature; especially, the average temperature of the third and forth month after transplantation is above25℃and the sunshine, heat and rainfall match well. Those are conducive to the growth of tobacco plant and dry matter accumulation which lay a favorable foundation for producing high quality flue-cured tobacco. During the maturation stage, the traits of the suitable temperature, relatively less sunshine hours and moderate relative air humidity are in favor of the maturity of tobacco and also set the seal on the special aromas types of tobacco in Xiangxi.The climatic suitability index of tobacco growing areas in Xiangxi is relatively high. And that area is the most appropriate for planting flue-cures tobacco because sunshine, temperature and rainfall go well with the requirements for producing high quality tobacco there.2. Environment features and evaluation of cultivated land resources and soil nutrient status of tobacco growing area in Xiangxi.This research has made comprehensive analysis on soil nutrient status of tobacco growing area in Xiangxi, and has clarified the distribution of soil nutrients in different regions.(1) The PH value of planting tobacco soil in Xiangxi is in weak acid to neutral, and the PH value of majority planting soil can satisfy the production of high quality tobacco leaves. Part of the soil, especially the one’s PH value is under5.00(make up12.09%), which are supposed to adjust soil acidity by using lime or dolomite fines.(2) Generally, the content of organic matter, alkali-hydro nitrogen, and available phosphorus in tobacco-growing soil of Xiangxi is proper with the average of2.16%,97.37mg/kg and35.354mg/kg; but the total phosphorus content of that soil is low with the average of0.065%; rapidly-available potassium content is extremely low, with the average of183.675mg/kg; the difference of magnesium content of various tobacco-panting soil is huge, with some parts in lack of magnesium and other parts abundant with magnesium, with the average of177.76mg/kg. Meanwhile, sulfur content of part of the tobacco growing soil is on the high side, with the average of30.731mg/kg; and effective boron content of most tobacco planting soil is sufficient, and effective boron content of only a small part of tobacco growing soil is in deficiency, with the average of0.728mg/kg. The main tobacco growing soil in Xiangxi is rich in effective copper and effective zinc, but it is lack of water soluble chloride as a whole, with the average of2.125mg/kgN2.06mg/kg and23.807mg/kg respectively..As a result, the local actual situation should be considered when flue-cured tobacco of various tobacco growing areas in Xiangxi is fertilized. According to the satiation of soil nutrition content, principles of the combination of "organic and inorganic","reduce and control nitrogen" and "supply and adjust phosphorus","increase and stabilize potassium","fill and manage chlorine" are implemented. At the same time, increasing the application of magnesium fertilizer and boron fertilizer properly to promote the sustainable development of tobacco leaves.3. Flue-cured tobacco’s quality features and comprehensive evaluation of the quality in Xiangxi tobacco area.Methods of comparison, analysis of variance, interpolation method of IDW in geostatistics and comprehensive evaluation have been adopted to research the characteristics of basic statistics of the appearance quality, physical property, chemical component, sensory quality of flue-cured tobacco in major tobacco-growing area in Xiangxi and differences in various tobacco planting counties and towns.(1) Appearance quality index:the index of flue-cured tobacco at B2F grade in Xiangxi ranges from67.7to84.6and the average value is77.13; the index of tobacco at C3F grade ranges from70.80to85.27and the average value is79.90; the index of tobacco at X2F grade ranges from50.77to77.97and the average value is72.63. The area with the highest index of tobacco at B2F grade is Baojing county; and the area with the lowest index is Huayuan county. The area with the highest index of tobacco at C3F grade is Fenghuang county; and the area with the lowest is Luxi county. The area with the highest index of tobacco at X2F grade is Yongshun county; and area with the lowest is Luxi county, the spatial distribution of the index of Xiangxi tends to decline from west to east.(2) Physical property index: In the upper part of Xiangxi (B2F grade), the index of tobacco is averagely from73.89to79.11. The area with the highest index is Guzhang county, and the area with the lowest index is Baojing county. In the middle part, the index of tobacco is averagely from86.44to88.33. The area with the highest index is Baojing county, and the area with the lowest index is Huayuan county. The spatial distribution of the index of Xiangxi tends to patch. As a whole, with regard to the physical property of tobacco growing area, the north part is better than the south part.(3) Chemical Component Usability Index:the CCUI of the flue-cured tobacco in Xiangxi is C3F>B2F>X2F, most of them are between the level of good-better, but some individual samples are at the level of not good enough. The CCUI at B2F in Luxi county was the highest, and Yongshou county was the lowest, it has the trend of decrease gradually from southeast to northeast; The CCUI at C3F in Luxi county was the highest, and Huahuan county was the lowest, with a trend that decrease gradually from Southeast to West; The CCUI at X2F in Luxi county was the highest, and Fenghuang county was the lowest, with a trend of decreasing gradually from Southeast to West.(4) Sensory quality index:The average sensory quality index of tobacco leaves in Xiangxi is72.51, the minima is63.02, and the maxima is89.23. The average sensory quality index of seven major tobacco growing counties are between66.13-80.37, which Guzhang county was the highest, and Fenghuang county was the lowest. The spatial distribution of the sensory quality index tends to increase from the southwest and northeast part to the central region.(5) Tobacco leaves quality index:the average index in Xiangxi is73.08and the lowest index is62.21; the highest index is85.21. The average index in seven major tobacco-growing counties ranges from67.13to78.22. The area with the highest index is Luxi county; and the area with the lowest index is Huayuan county. The index of major towns producing tobacco ranges from62.21to82.71. The area with the highest index is Liexi town; and the area with lowest index is Dong Maku town. The spatial distribution of the index tends to increase from the southwest and northeast region to the central region.4. The relation between tobacco leaves quality and ecological factors in Xiangxi tobacco growing area.(1)The relation between chemical composition and ecological factors.The sunshine duration in the field growing period (x1), the average temperature of the field growing period (x2), the amount of precipitation in the field period (x3), and the daily range of temperature in the field growing period (x5) make great influence in chemical composition, especially on total sugar, reducing sugar, total nitrogen, and nicotine chemical composition(indicators). The edaphic factors, such as PH (x1), total nitrogen (x3), total phosphorus (x4), total potassium make great influence on chemical composition, especially on total sugar, reducing sugar, nicotine, total nitrogen, and chemical composition (indicators).(2) Physical characteristics and ecological factors.Meteorological factors, especially the sunshine duration of the field growing period (x1), the average temperature during the field growing period (x2), the amount of precipitation d uring the field growing period (x3) have a great influence on the physical properties of tobac co leaves, mainly in the physical quality indexes, such as in the leaf length (yl), leaf width (y2), open degree (y3), stem weight (y5), simple weight (y4), and the quality of unit leaf area (y9). Edaphic factors, like PH value (x1), followed by total N (x3), total K (x5), have more ef fects on the physical properties of tobacco leaves, which mainly lies in the split pieces (y3),1eaf weight (y4), stem weight (y5), stem ratio (y6), equilibrium moisture content (y1), and oth er physical indicators. |
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