| Mountain area is the major producing areas of flue-cured tobacco, including mountain area of Guizhou, Yunnan, Chongqing and so on, where more than 1.5 × 109 kg of flue-cured tobacco is produced. Mountain area of tobacco has an obvious regional characteristic of three-dimensional climate, that is even in the same city(or county), its tobacco shows different chemical physical properties and quality. Therefore, tobacco yield of mountainous area can not only meet the needs of cigarette industry, but also can meet the requirement of different quality of tobacco leaf. According to the micro-topography characteristics of tobacco area on Yunnan-Guizhou Plateau and combined with slope position, slope degree and elevation height and other factors, mountain cultivated soils can be divided into three kinds of typical micro-topography unit, including dam, sloping fields and platform. Through core plot experiment and soil displacement test at Dafengdong of Kaili City, and demonstration test in other typical tobacco planting zones such as Dejiang, Xingyi, Kaiyang, Xixiu in Guizhou Province, the soil environment of tobacco, field microclimate characteristics of tobacco, and their influence on growth and development, and quality of tobacco leaves are analyzed thoroughly, which provided a theoretical reference for tobacco production and brand orientation of cigarette industry in the mountain areas and at the same provided scientific guidance of high yield and good quality of mountain tobacco production for southwest mountainous tobacco planting area especially for Guizhou mountainous tobacco planting area of the main three micro-topographies. The main results were as follows:1. Analysis of field microclimate characteristics in different micro-topograpies planted with tobaccoCanopy average temperature of dam, sloping fields and platform was 22.5 ℃, 22.14 ℃ and 21.88 ℃, respectively, in growth period and daily variation difference of air temperature in different micro-topograpies at topping stage was reached very significant level. Surface average temperature of dam, sloping fields and platform was 23.96 ℃, 23.66 ℃ and 23.34 ℃, respectively, in growth period, and surface temperature of sloping field has a tendency to escalate in accordance with the growth period, but that of dam and platform has a "high- low- high- low" trend, and to reach maximum at harvesting stage of the second tent leaf.The daily variation of relative field humidity of different treatments was in almost the same, and showed the bimodal curve rule of inverted "W" type. In addition to average relative humidity of dam > platform > sloping fields at the group stage, the rest of the growth period was characterized by platform > dam > sloping fields. The average of CO2 concentrations for dam, sloping field and platform was 316.3 mg·kg-1, 236.5 mg·kg-1 and 232.08 mg·kg-1, respectively. Range(251.2 mg·kg- 1) and the coefficient of variation(26.91%) of sloping fields was the largest of three micro-topographies, next to platform, and the minimum for dam. The wind speeds were 0.198 m/s, 0.261 m/s and 0.229 m/s, respectively, in dam, sloping fields and platform.The change trend of scattering light intensity above canopy was dam < sloping fields < platform at group stage or topping stage, and that was dam < platform < sloping fields at harvesting stage of the second tent leaf and upper leaf harvesting stage.Average value of original visible spectral reflectance was that sloping tobacco < platform tobacco > dam tobacco during mature stage and that was platform tobacco < sloping tobacco < dam tobacco during the rest periods. The spectral curve linear was similar to each treatment, and its reflectivity was low in < 710 nm visible part, and also formed "green mountain" near 550 nm because of chlorophyll reflection on green light. The first derivative spectra wavelength was "red edge" between 690-710 nm and its height was that platform tobacco < sloping tobacco < dam tobacco.2. Analysis of soil environment characteristics for flue-cured tobacco planted in different micro-topograpiesSoil relative water content in dam is highest(55.08%) during period of flue-cured tobacco growth, followed with that in sloping fields(51.22%), and the lowest(49.96%) in platform. Rainfalls in dam and platform mainly affect the moisture content at 40 cm soil layer, but that of 30 cm soil layer in sloping fields. The difference at depths in sloping fields is most sensitive to rainfall, followed by platform, and the most insensitive response for dam of the three micro-topographies.Soil temperature of dam was the highest, and soil temperature range of 4 layers of dam was the lowest of the three micro-topographies. Soil temperature range of 20 cm ~ 30 cm soil layer of platform was the highest. 10 cm ~ 30 cm and 30 cm ~ 40 cm soil layer was its temperature disturbance layer. The soil average temperatur of dam was the highest, next to that of platform, and that of sloping fields was slightly below to that of platform in sunny. Comparison of soil temperature range of 4 layers for the three micro-topographies in rainy days, it showed platform > sloping fields > dam.Microbial quantity was characterized by dam > sloping fields > platform, and the increasing proportion of fungi, actinomycetes and bacteria was 13.23%, 9.57% and 13.23%, respectively, for sloping fields more than platform, and the corresponding proportion was 36.54%, 25.73% and 29.79%, respectively, for dam more than platform.The average content of p H value, organic matter, available nitrogen, available phosphorus, available potassium was characterized by dam > sloping fields > platform, and the difference between micro-topographies in general was extremely significant. In addition to significant level for difference of available nutrient content between sloping fields and platform, the remaining difference had reached extremely significant level.The range and the numerical of soil H2O2 enzyme activity was larger before mature period(68 days after transplanting), and that was smaller after maturation, and the trend was basically characterized by dam > sloping fields > platform. The trend of urease activity was also characterized by dam > sloping fields > platform in growth periods.The trend of soil sucrose activity was characterized by dam > sloping fields > platform in rest of growth stages, except that soil sucrose activity of platform was slightly greater than that of sloping fields at rooting stage and soil sucrose activity of treatments had ups and downs before topping stage. The difference had reached significant level above between dam and sloping fields, sloping fields and platform.Micro-topography factors and soil factors had both an impact on soil nutrient, soil microbial quantity and soil enzyme activities, but the influence of micro-topography factors was more than soil factors, that was to say the micro-topography was the dominant factor affecting the soil environment.3. Analysis of growth and physiological characteristics in leaves of tobacco planted in different micro-topograpiesGrowth period of dam tobacco plant was 9 days in advance of that of sloping fields tobacco plant, and 7 days in advance of that of platform tobacco plant. It was characterized by dam > sloping fields > platform for maximum leaf length, maximum leaf width, plant height, stem circumference, pitch, leaf area index in growth periods. Maximum leaf length / width was characterized by dam(2.38) < sloping fields(2.413) < platform(2.414). It was characterized by dam > sloping fields > platform for fresh weight of roots, stems and leaves, dry weight of tobacco plant. Accumulation intensity of tobacco plant fresh matter reached peak 1 week before topping stage. The fresh matter accumulation accounted for 67.41%, 61.66 and 61.08%, respectively, of the total strain for tobacco of dam, sloping fields and platform. The difference of tobacco fresh biomass was significant among the micro-topographies. The root-shoot ratio of dam and sloping tobacco on the whole was greater than that of platform tobacco, and that of dam and sloping tobacco was almost equal.In stretch root stage and fast growing stage, the root activity showed that dam > sloping fields > platform, and the root activity showed that sloping fields > platform > dam in mature stage. Growth of root system was characterized by dam > sloping fields > platform, and the difference of root growth indicators among the micro-topographies reached significant level on the whole.The trend of Amylase(AMS) activity, sucrose activity was characterized by dam > sloping fields > platform in rest of growth stages, and difference had reached significant level above among the micro-topographies. Sucrose synthetase(SS) activity of tobacco was first increased and then decreased with the single peak curve, its trend was platform tobacco > sloping tobacco > dam tobacco, and the difference was significantly for micro-topographies in late growth stages. Sucrose phosphate synthase(SPS) activity of tobacco leaf also showed a single peak curve, but to reach the maximum value at the prosperous stage, and SPS activity of dam tobacco leaf was significantly higher than that of platform tobacco leaf, and the difference was significantly among micro-topographies at the mature period. Stomatal conductance(Gs), Nitrate reductase(NR), Superxiode dismustase activities(SOD), Peroxidase activities(POD), Catalase(CAT) activity was characterized by dam > sloping fields > platform before mature stage and that was sloping fields > dam > platform during mature stage, and difference had reached significant level above among the micro-topographies.The change of Photosynthetically active radiation(PAR), Net photosynthesis rate(Pn), Stomatal conductance(Gs) and Transpiration rate(Tr) of tobacco leaf during the whole growth period showed a "parabola" trend, and these indexes were that platform tobacco < sloping tobacco < dam tobacco at spherical plant stage, fast growing stage, topping stage and that dam tobacco < platform tobacco < sloping tobacco at the mature stage. The change of intercellular CO2 concentration(Ci) of dam tobacco showed ascendant trend during the whole growth period, but that of sloping tobacco and platform tobacco was a floating trend of "low-high-low-high". The Water use efficiency(WUE) change of dam tobacco and sloping tobacco was a trend of " high-low-high-low", but that of platform tobacco showed decendant trend during the whole growth period. Temperature of leaf(TL) was characterized by dam > sloping fields > platform before mature stage and that was platform > sloping fields > dam during mature stage.Comparison of yield and output value of flue-cured tobacco treatments on micro-topographies, it was characterized by dam > sloping fields > platform. Compared with platform, yield and output value of dam tobacco increased by 29.66% and 41.8%, respectively, and the corresponding ratio for slope tobacco increased 14.82% and 30.38%, respectively. Tobacco yield reached the extremely significant difference between dam and platform, and they both reached significant differences with sloping fields; The output value reached the extremely significant difference between tobacco treatments on micro-topographies.The average price, superior tobacco proportion and superior-medium proportion of flue-cured tobacco was characterized by sloping fields > dam > platform. The lower proportion of flue-cured tobacco was characterized by platform > dam > sloping fields, and compared with platform, lower tobacco proportion of dam tobacco and slope tobacco reduced by 29.07% and 55.19%, respectively.Correlation and regression analysis was carried out on the yield and output value, respectively, the results showed that: Yyield = 0.298 Xplant height + 0.223 Xstem fresh weight + 0.303 Xaverage root diameter – 0.088 Xtotal root volume – 0.122 XTa + 0.157 XAMS + 0.584 XNR + 0.125 Xnumber of bacteria – 4.104E-16; Youtput value = 0.586 Xmaximum leaf length – 0.403 Xstem circumference – 0.021 Xroot activity of fast growing stage + 0.206 XE – 0.067 XRH + 0.067 XAMS – 0.586 Xeffective phosphorus + 0.547 Xnumber of actinomycetes – 1.112E-15. NR activity of topping stage, average root diameter and plant height had a bigger contribution to tobacco yield, and AMS activity, length of maximum leaf, number of actinomycetes had a bigger contribution to output value of tobacco. These environmental factors among micro-topographies reached significant difference which affected the yield and output value of flue-cured tobacco.For yield of tobacco, dam tobacco had has higher photosynthetic capacity in growth period, accumulated more dry matter, and formed the basis of production. And its high carbon and nitrogen metabolism was regarded as physiological basis. The two aspects was both in the center level with sloping tobacco, but platform tobacco was the worst. So dam tobacco owned higher yield, and sloping tobacco had optimum yield.4. Analysis of quality characteristics for flue-cured tobacco planted in different micro-topograpiesTotle scole, aroma quality, irritancy, taste, aftertaste, fine flexibility and combustibility, gray score was characterized by sloping tobacco > dam tobacco > platform tobacco at Kaili test site. Amount of aroma score was characterized by dam tobacco > sloping tobacco > platform tobacco. The aroma type for sloping tobacco was “middle but partial fragrance”, and that of dam tobacco and platform tobacco was “middle flavor”. The main aroma for sloping tobacco was “significant” and “more significant”, while that of dam tobacco and platform tobacco was “more significant” and “yet significant”, and auxiliary aroma included “fruit” component in addition to "woody", "spicy" for sloping tobacco. Total score of 5 smoking index of middle tobacco leaf was characterized by sloping tobacco > platform tobacco > dam tobacco at Kaili test site and 5 demonstration sites such as Kaiyang, Xingyi, Dejiang, Xixiu and Guiding, and index of aroma quality, amount of aroma, taste, mixed gas, irritancy was the highest to sloping tobacco, and was slightly higher for platform tobacco than dam tobacco.Content of aroma substance for middle leaves was that sloping tobacco > dam tobacco > platform tobacco, and it was that sloping tobacco > platform tobacco > dam tobacco for upper leaves and lower leaves at Kaili test site. Content of westpac alkanes, alkaloids, chlorophyll degradation products was the highest for sloping tobacco, and content of aroma substance for middle leaves was that sloping tobacco > dam tobacco > platform tobacco at six demonstration sites in Guizhou.Per leaf weight of upper leaves and middle leaves was that dam tobacco > sloping tobacco > platform tobacco, and it was that sloping tobacco > platform tobacco > dam tobacco for lower leaves at Kaili test site. Stalk ratio of flue-cured tobacco was that dam tobacco > platform tobacco > sloping tobacco, and difference had reached extremely significant level between lower leaves at dam and platform, dam and sloping fields. Index of middle leaf length, leaf width, per leaf weight, leaf density was that dam tobacco > sloping tobacco > platform tobacco, and the lowest for sloping tobacco at demonstration sites, such as Kaiyang, Xingyi, Dejiang, Xixiu, Guiding.Content of total nitrogen, nicotine, total sugar, reducing sugar was that dam tobacco > sloping tobacco > platform tobacco for different growth stage tobacco or flue-cured tobacco. Sucrose content of tobacco leaf showed a wave curve and was low at spherical plant stage, but achieved maximum at fast growing stage, and its trend was that platform tobacco > sloping tobacco > dam tobacco, which decreased at topping stage and rose at mature stage. Potassium content had been gradually reduced with growth period, and it showed that sloping tobacco > dam tobacco > platform tobacco. the increasing proportion of potassium content of upper, middle, lower tobacco leaf was 13.89%, 2.21% and 13.73%, respectively, for dam tobacco more than platform tobacco, and the corresponding proportion was 31.48%, 27.94% and 62.09%, respectively, for sloping tobacco more than platform tobacco. Chlorine content of tobacco during the growth periods and after baking was that sloping tobacco > dam tobacco > platform tobacco. And difference of chemical composition had reached significant level in the upper and lower tobacco leaf for different micro-topographies, and even extremely significant for middle tobacco leaves.Ratio of potassium to chlorine was more than 4, ratio of nitrogen to alkali was close to 0.9 ~ 1.1, ratio of sugar to alkali was close to 8 ~ 10, ratio of two sugar was close to 0.9 ~ 1.0 for sloping middle tobacco leaf, was the best suitable range of high quality tobacco leaves. But ratio of nitrogen to alkali, ratio of two sugar was slightly less than the appropriate range for dam tobacco and platform tobacco.Content of nicotine, total nitrogen, total sugar, reducing sugar was characterized by dam tobacco > sloping tobacco > platform tobacco at demonstration sites, such as Kaiyang, Xingyi, Dejiang, Xixiu and Guiding. Content of potassium was the largest for sloping tobacco, and that of dam tobacco, platform tobacco had ups and downs at different pilot sites. Content of sloping tobacco was basically located in or close to the appropriate scope, but content of dam tobacco or platform tobacco was below the appropriate range.Through regression analysis between smoking total score and index of other sensory evaluation indicators, the field microclimate, chemical component content, chemical composition of coordination index, aroma substance content, respectively, their respective regression model equation was set up finally. The results showed that taste, wind speed at two shed leaf harvesting stage, potassium content, ratio of potassium to chloride and total aroma substances was larger influence on sensory smoking quality of tobacco leaves. These environmental and quality factors among micro-topographies reached extremely significant difference which affected sensory quality of flue-cured tobacco.For aspect of tobacco quality, compared with dam tobacco or platform tobacco, sloping tobacco had advantage of altitude, owned ventilation pervious to light, higher aroma matter content, better coordination of chemical composition, which could promote the formation of tobacco leaf quality. So sloping tobacco had higher quality.In short, developing of sloping tobacco production, that is high quality and optimum yield, had a realistic and strategic significance. It could not only well satisfied with the need of quality to cigarette industry in the first place, and also avoided land competition between food and tobacco. Production of sloping tobacco made more flat and fertile soil to develop grain production. |
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