| By using serial field survey and laboratory analyses,we collected 604 soil and tobacco samples in 9 typical tobacco planting districts in mid-altitude area of red earth in Qujing of Yunnan province,the distribution characteristics of soil available zinc and zinc in tobacco leave were analyzed,the influence of soil factors(Zn,p H,organic matter,P,Ca)on zinc in flue-cured tobacco were studied,and the relationship between tobacco zinc and the quality indicators(appearance quality,physical properties,chemical composition,sensory quality)were studied.The main result were as follows.1.The distribution of soil available zinc content in mid-altitude area of red earth in Qujing was analyzed.The soil available zinc content ranged from 0.14mg/kg to 21.68 mg/kg with the average content was(3.02±2.88)mg/kg in this area,the variation coefficient was 95.29%.The area of available zinc deficiency(<1.0 mg/kg)was only 8.78% in this area,which can not meet the needs of tobacco growth;72.68% of the soil zinc content(1.0~4.0 mg/kg)can meet the needs of high quality tobacco growth;18.54% of the soil zinc content was high(>4 mg/kg).The soil available zinc content in different tobacco planting areas were quite different.The soil available zinc content in Xuanwei,Huize and Zhanyi was relatively high,which were 10.84 mg/kg,5.75 mg/kg and 4.97 mg/kg.The soil available zinc content in Fuyuan was the lowest with 1.87 mg/kg;The soil available zinc content in other areas was between 2.08~3.35 mg/kg,and the difference was not significant.2.The characteristics of zinc content in flue-cured tobacco leaves in mid-altitude area of red earth in Qujing was studied.The results showed that:(1)The zinc content in flue-cured tobacco leaves ranged from16.66 mg/kg to 109.89 mg/kg with the average content was 46.35 mg/kg,the variation coefficient was 35.44%.There was 68.38% of the tobacco leaves zinc content was in the suitable range(20.0~50.0 mg/kg),22.19% of the tobacco leaves zinc content was at a high level(50.0~70.0 mg/kg),0.49% of the tobacco leaves zinc content was deficiency.The proportion of zinc content in tobacco leaves in this area is in line with the general range of zinc content(20.0~80.0 mg/kg)in China's tobacco is 94.54%;But the proportion of tobacco samples in accordance with the standard of zinc content of high quality tobacco leaves in Brazil(10.15~31.64 mg/kg)is only 15.27%.(2)There zinc content in tobacco leaves was different in different areas: Zhanyi > Xuanwei > Huize > Malone >Qilin > Luliang > Luoping > Fuyuan > Shizong.The zinc content in tobacco leaves in Zhanyi,Xuanwei and Huize were the highest,which respectively were 74.96 mg/kg,69.19 mg/kg,69.02 mg/kg,and there was a very significant difference from other tobacco growing areas;The zinc content in flue-tobacco leaves in Luoping,Fuyuan and Shizong were low and the difference is significant.The zinc content deficiency areas were 1% in Luoping and Shizong.(3)The zinc content in tobacco leaves was significantly different among 5 different flue-cured tobacco varieties.Hong Da> Yunyan 87 > Yunyan 85 > Yunyan 97 > K326.The zinc content of flue-tobacco leaves of Hong Da was the highest with(68.10±16.56)mg/kg,and there was a very significant difference from other Flue-cured Tobacco Varieties;the second was Yunyan 87,and the difference was very significant;the zinc content in K326 was the lowest with(40.01±9.23)mg/kg,there was no significant difference from Yunyan 85 and Yunyan 97.The zinc content of flue-tobacco leaves were abundant of different flue-cured tobacco varieties,except that there was a very small part(1.71%)of Yunyan 85 was lack of zinc.3.The effects of soil factors on the content of zinc in tobacco leaves in mid-altitude area of red earth in Qujing were analyzed.(1)The zinc content in tobacco leaves were significantly different among different components after the soil available zinc content was grouped.The zinc content of tobacco leaves increased with the increasing of soil available zinc content.When the soil available zinc content was less than 4.0 mg/kg,the zinc content in tobacco leaves increased with soil available zinc content was very slowly;when the soil available zinc content is greater than 4.0 mg/kg,the increasing trend was speeded,and there was a significant difference from other components.For some tobacco fields with high zinc content,we can control the application of nitrogen fertilizer,reduce organic manure,or use alkaline fertilizers such as calcium,magnesium and phosphorus,so as to avoid excessive zinc and poisoning tobacco plants.(2)The soil p H was 6.21,and ranged from 4.34 to 8.19.The proportion of soil p H suitable for the growth of flue-cured tobacco(5.0~7.0)was 73.84%,the proportion of soil p H in the most suitable range of tobacco growth(5.5~6.5)was 39.07%.The relationship between the content of tobacco leaf zinc and soil p H was negative correlation,with the increasing of soil p H,the zinc content of tobacco leaves decreased.When soil p H <6.5,the zinc content in tobacco leaves decreased significantly in each component,and then the decreasing trend was slowed with the increasing of soil p H.(3)The organic matter content was 3.61%,and ranged from 0.61% to 8.19%.The content of soil organic matter in 5.13% tobacco growing areas was at a low level(<1.5%),The content of soil organic matter in 49.83% tobacco growing areas was at a high level(>3.5%).The zinc content in tobacco leaves gradually decreased with the increasing of soil organic matter content,and there was a great difference in the content of zinc in tobacco leaves among different soil organic matter components.(4)The soil available phosphorus content was 30.53 mg/kg,and ranged from 0.13 mg/kg to 109.93 mg/kg.The content of soil available phosphorus content in 39.24% tobacco growing areas was at a low level(20.0 mg/kg),and 25.16% tobacco growing areas was at a high level(20.0 mg/kg),only 35.60% of soil available phosphorus content was at a suitable level(20.0~40.0 mg/kg).The relationship between the zinc content in flued-cured tobacco leaves and soil available phosphorus was negatively correlated,and the correlation coefficient is-0.262**,the zinc content in tobacco leaves decreased with the increasing of soil available phosphorus,the relationship between phosphorus and zinc was antagonism.(5)The soil exchangeable calcium content was 2395.32 mg/kg,ranged from 431.57 mg/kg to 8273.71 mg/kg.The proportion of soil exchangeable calcium in suitable range(800~1200 mg/kg)was only 11.75%,the proportion of soil exchangeable calcium in a high level(>1200 mg/kg)was 84.76%.The zinc content in tobacco leaves decreased with the increasing of soil exchangeable calcium content.When the soil exchangeable calcium content was less than 2000 mg/kg,the zinc content in tobacco leaves has a significant difference among all the components.When calcium and zinc are combined,the maximum adsorption capacity and binding constant of zinc in soil decrease,and the degree of reduction decreases with the increase of calcium concentration.(6)The relationship between the zinc content in flued-cured tobacco leaves and soil total phosphorus,total potassium,available nitrogen,available Cu,Fe,Mg,Mn,S has a positive correlation,and the correlation were very significant between soil available Cu,Fe,Mn,with available Mg reached 5% significant the level;The relationship between the zinc content in flued-cured tobacco leaves and soil total nitrogen,available boron has a negative correlation,and the correlation was very significant between the total nitrogen.4.The relationship between the zinc content in tobacco leaves and the quality of tobacco leaves in mid-altitude area of red earth in Qujing were studied.The zinc content in tobacco leaves was divided into four grades,lacking(<20.0 mg/kg),suitable(20.0~50.0 mg/kg),higher(50.0~70.0 mg/kg)and sky-high grade(>70.0 mg/kg),and analyzed the relationship between the zinc content in tobacco leaves and the quality of tobacco leaves.The results showed that: With the increasing of zinc content in tobacco leaves,the score of the appearance quality of tobacco increased,when the zinc content in tobacco leaves is in the high component,the appearance quality was the best,but there was no significant difference between the ‘suitable' and ‘high' components;The weight,length,density and filling value of the tobacco leaves were all increased with the increasing of zinc content in tobacco leaves,when the zinc content in tobacco leaves was in the ‘suitable' and ‘higher' component,the physical characteristics of tobacco was the best;The total sugar,reducing sugar,total nitrogen,nicotine and petroleum ether extract increased with the increasing of zinc content in tobacco leaves,but the content of kalium decreased,the content of chlorogenic acid and rutin was significantly correlated with the content of zinc in tobacco leaves,there was no significant correlation between the volatiles of tobacco leaves and the zinc content in tobacco leaves;With the increasing of zinc content in tobacco leaves,the scores of each index of sensory quality of tobacco leaves increased.When the zinc content in tobacco leaves was ‘suitable'(20~50 mg/kg)and ‘higher'(50~70 mg/kg),the quality of tobacco leaves was the best. |
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