| Chaling is located in the east of Hunan province.It is located in the west of the Hunan and jiangxi Chaling County is located in the east of Hunan Province,at the border of Hunan and Guizhou,and at the west of the Luojing Mountains,and is a part of Zhuzhou City.It belongs to the humid subtropical monsoon climate and it is planted with 20,000 mu of flue-cured tobacco all year round.It is a typical tobacco-paddy rotation area in southern Hunan.Chlorine deficiency in the production of flue-cured tobacco in Chaling County was studied in this research.Then,the annual differences,which is inthe levels of B2F,C3F,and X2F in flue-cured tobacco,and correlation with climatic factors was analyzed from 2012to 2016 in Chaling.Besides,the spatial distribution map of the main indicators of tobacco-planting soil fertility was drawn in Chaling.Furthermore,the scope of safe chlorine application was explored by performing the test of adding chlorine fertilizer on representative soils,while improved fertilization scheme was proposed.Finally,Chloride absorption kinetic parameters was studied.The main findings are as follows:1,The content of total sugar and reducing sugar in flue-cured tobacco County is relatively high in Chaling,so is the content of nicotine in upper leaves.The results show that the content of total nitrogen is appropriate,and the content of chlorine and potassium is low.The highest score of tobacco at the top leaves was 58.37 in 2012,60.27 at the middle in 2013,and 57.60 at the bottom in 2013.The best internal quality appeared in 2012.The highest appearance quality of tobacco leaves in the upper,middle and bottom parts the appeared in2013.The quality of flue-cured tobacco is correlated with the temperature and rainfall of the year.The periods which leaves of different parts appear is different.The temperature and the rainfall during the growth of leaf growth is correlated with roasted quality.It shows that the temperature is the basis of growth and can affect the number of leaves of the tobacco plant,and the moisture is the decisive factor in the current period,which affects the growth,development and maturation of the leaves that have emerged.The annual rainfall was more appropriate in 2012 and 2013.Less rainfall and suitable temperature made tobacco grow better in the early stage of flue-cured tobacco production.Meanwhile,the longer rainfall in all years was good for tobacco leaf material accumulation.The higher temperature is more conducive to the maturity of the upper leaves with the rainfall.At the same time,the relevant climatic factors were indicated that the chlorine content in the leaves was closely related to the precipitation,because the chloride ions brought by rainfall were absorbed into tobacco leaves.2,The average temperature is 22.22?,then the temperature rose steadily with the growth of flue-cured tobacco during the growth of tobacco field.While an average rainfall is1050.05mm during the entire growth period flue-cured tobacco in Chaling.The rainfall was the longest in May with an average of 274.3mm,and the lowest rainfall in July was158.26mm.In the months of March,April and June,the average value of rainfall was within the range of 204 to 208 mm.The rainfall can meet the demand for the growth and development of flue-cured tobacco.Compared with the demand of the moisture of them,more rainfall at early stage and easier compaction of soil is not conducive to the early growth of the tobacco plant.The rainwater is beneficial for the growth of high-quality tobacco after resettling stage,thus agronomic measures,such as high ridge in a field and covering terra,alleviate the situation of excessive rainfall in the early stages in these rotation area.3,Chlorine content,with an average of 14.47 mg·kg-1,of tobacco-planting soil is appropriate in Chaling.There is no shortage of chlorine,but the coefficient of variation of soil chlorine content reaches 85%,which indicating that is a big difference between towns and villages.According to the frequency of suitability distribution,there is 50.8%of the soil in the tobacco plant is very low in chlorine.4,In 2015,the soil has lower pH?5.49?and richer organic matter and nitrogen,while67.6%of the soil is deficient in phosphorus and potassium in Chalin.The content of trace elements in copper,iron,zinc and boron was relatively high,meanwhile the content of sulfur,magnesium and manganese is more suitable,and the content of chlorine is lower in Chaling.The spatial distribution of soil nutrients varies greatly from town to village.On the whole,the most suitable planting area is Majiang Town and Zaozuo Town in Chaling County.The biggest restricting factor of planting in Huotian Town is that the pH is too low in soil and it is necessary to pay attention to soil alkaline improvement.In terms of time,there is a tendency of acidification in tobacco-planting soil,soil pH decreased by 0.33 units over 6years compared with 2009.And the organic matter and effective sulfur content increase significantly.In 2009,the organic content of planting soil in the county was 22.59g·kg-1.By2015,the average organic content reached 37.64g·kg-1;in 2015,soil sulfur content was increased by 3.3mg·kg-1,3.11mg·kg-1,18.33mg·kg-1,7.18mg·kg-1,and 10.9mg·kg-1,13.85mg·kg-1,17.58mg·kg-11 and 9.37mg·kg-11 in Huotian,Zhitang,Gaolong,Yaopi,Zaoshi,Jieshou and Majiang towns,respectively.5,The effect of different chlorine application amount on the yield and quality of flue-cured tobacco was studied by using a plot with low chlorine content in the tobacco-paddy rotation area.The results showed that the yield,output value,average price,and middle-upper ratio of the flue-cured tobacco respectively was 2233.42kg·hm-2,53446.55yuan·hm-2,23.93yuan·kg-11 and 82%with 22.5kg·hm2 of chlorine fertilizer.From the economic point of view,the differences were not significant between T2 and T3.Compared with no application of chlorine fertilizer,the growth period was extended by 2days with 15 to 30kg·hm-22 of chlorine fertilizer,while 5 days with 37.5 to 45 kg·hm-22 of chlorine fertilizer.Appropriate supplemental application of chlorine fertilizer can increase the agronomic traits of flue-cured tobacco.When the application amount of chlorine fertilizer was 30kg·hm-2,the plant height was 114.0cm,the maximum leaf length was72.9cm and the stem circumference was 9.2cm.It showed that the most favorable application of chlorine fertilizer was 22.5-30kg·hm-2for the improvement of tobacco leaf production and quality.6.Different varieties of flue-cured tobacco has some differences in the absorption stage and absorption capacity of chloride ions.The chlorine content in different parts of different varieties was increased with chlorine.The content of chloride ion was increased with the increase of chlorine fertilizer in the mature tobacco leaves of different varieties.The chlorine content of tobacco leaves in G80 was the highest in all varieties.The basic rule of chloride ion content in different parts was upper>middle>bottom.Chlorine content is suitable at the middle tobacco leaves with 15 kg·hm-2-60kg·hm-22 of chlorine fertilizer.While the chlorine content is low at the bottom leaves,it needs 20 kg·hm-270kg·hm-2of chlorine fertilizer.The physical characteristics of tobacco leaves after curing are different with different chlorine treatments.The appropriate amount of chlorine can improve the physical characteristics of the leaves.At the upper leaves,there were the largest length in T4,the largest width in T2,the largest single leaf weight in T5 and the lowest stem ratio in T2.At the middle leaves,there were the largest length in T4,the largest width in T5,the largest single leaf weight in T4 and the lowest stem ratio in T3.At the bottom leaves,there were the largest length in T3,the largest width in T5,the largest single leaf weight in T5,and the lowest stem ratio in T3.In general,Application of potassium chloride(60kg·hm-2)in T4 is the best.7.There are significant differences in the absorption rate and affinity of chlorine in different varieties of flue-cured tobacco.When the content of chlorine in the environment is low,K326 has higher chlorine absorption rate and higher affinity than Yunyan 87,while the absorption capacity of Yunyan 87 is stronger when the concentration of environmental chloride is high.Secondly,under different growth periods,the absorption rate of chlorine in the roots is significantly different,showing a tendency of rising first and then decreasing.The absorption rate reaches its maximum at about 35 days,and the chlorine absorption rate is reached the minimum at 25 days between treatments.The greater the concentration of chlorine in the medium,the greater the rate of chlorine absorption.The absorption kinetic parameters of chlorine in different growth periods shows that the greater the concentration of chlorine,the greater the Imax,Km,and Cmin values of chlorine absorption,and the greater the magnitude of changes in the parameters over times with the same concentration treatment. |
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