| Tobacco is an important economic crop in China. As one of the main tobacco-planted regions, there is an area of 47,000 hm~2 planting tobacco in Chongqing. Tobacco industry is not only the leading industry of breaking away from poverty but also the primary resource of finance and revenue in tobacco-planted regions in Chongqing. Currently, the lower quality tobacco and being short of competition in international market, is the most important problem of tobacco production all over the country. As a crop which should be paid equal attention to yield and quality, the quality of tobacco is subjected to soil, breed, planting technique, climate and cool technology, and etc. Especially the soil is the dominant factor. The reason is that the fitting soil fertilizer is the base of gaining high quality tobacco. However, the nutrient investigation of tobacco-planted soil in large scale has never been carried out in Chongqing, which results in the shortage of the theoretical basis on tobacco nutrient controlling. Tobacco growers carry out the balanced fertilization without consideration of the characters of soil and tobacco, which leads to the inconsistent nutrient and influences the further improvement of tobacco quality.Microelement is the key element in tobacco growth, and its content relates to tobacco quality intimately. The necessary microelements of B, Mo, Cl, Fe, Mn and Mg and heavy metals of Cu and Zn influence the color, aroma, taste and machining of tobacco. Moreover the excessive deleterious heavy metals of Cd, Pb, As, Cr, Hg directly affect its edible safety. So with the dual-function of nutrition and poison, the controlling of tobacco microelement nutrition is focused on deficient nutrient and excessive poisons, especially on the fit proportion between N, P, K and microelements. The key technical problems of assuring standardized tobacco production are the fit form and content of N and K and scientific fertilizing methods. So the study on the control of planting-tobacco soil key elements is theoretical significant. It helps to construct high quality tobacco bases, to improve tobacco quality and competition.Based on the technique of GIS, the method of field sampling, indoor analysis, field test and pot experiment, and the application of SPSS soft and mathematic models, this study analyzes and estimated the tobacco soil nutrition, and studies some key nutrients influencing on tobacco growth and quality. The results are as following: 1 The nutrient status and evaluation on planting tobacco soil in ChongqingNutrient of planting-tobacco soil in Chongqing was evaluated from region and type difference of soil by consulting abundant and lack indexes of soil nutrient of main crops and the second national soil survey in China, combining soil nutrient survey of main planting-tobacco areas and recent part results of field research, embodying requirement character of tobacco nutrient, applying abundant and lack indexes of soil nutrient and N-offered ability indexes of soil, and combining the whole nutrient status ofplanting-tobacco soils in Chongqing.The average pH of planting-tobacco soil in Chongqing was5.99, its variability was low and area of soil pH suitably planted occupied 49.8% of total areas. The average content of soil organic matter was25.13 g/kg, its variability was lower and suitable soil area reached to 50% of total areas. The average available N was54.6mg/kg, its variability was high and suitable soil area was 70% of total areas. The average available P wasl5.2mg/kg, its variability was high and suitable soil area was 34% of total areas. The average available K wasl56.8mg/kg, its variability was higher and suitable soil area was 84% of total areas. The average exchangeable Ca was9.81 cmol/kg, its variability was lower and suitable soil area only was 14% of total areas. The average exchangeable Mg was 1.17 cmol/kg, its variability was high and suitable soil area was 41% of total areas. The average available S was34.4mg/kg, its variability was higher and suitable soil area was 66% of total areas. The average available Zn wasl.9mg/kg, its variability was high and suitable soil area was 67% of total areas. The average available Fe was27.8mg/kg, its variability was high and suitable soil area was 94% of total areas. The average available Mn was 43.0mg/kg, its variability was high and suitable soil area was 95% of total areas. The average available Mo wasO.2mg/kg, its variability was high and suitable soil area was 33.4% of total areas. Calcareous soil was characterized by the highest contents of pH and exchangeable Ca, yellow brown soil by the highest contents of soil organic matter and available P, yellow soil by the highest content of available N, paddy soil by the highest content of available K, and purple soil by the highest contents of exchangeable Mg and available S. The highest and lowest content of heavy metalswere found in yellow brown soil and in calcareous soil.2 The potassium nutrient and its control of tobacco in ChongqingBy analyzing the influence of K on tobacco growth, element absorbing and quality, it is indicated that: The content of Chlorophyll and dry-matter gets increased with the increase of potassium application. And 300 mg/kg of potassium application is optimal content, which is best to tobacco dry-matter increasing. This conclusion is different in the northern China. In all treatments, the yield and quality are lower in the proportion of 7:3 of potassium application and the yield of superior tobacco rises in the proportion of 5:5. With considering the proportion of nitrogen and potassium, it is better in the proportion of 1:1:3 of nitrogen, phosphorus and potassium. The nitrogen application helps to augment the plant height and leaf area, to postpone the physiological periods and to increase the yield and value, as well as to improve the content of total nitrogen, nicotine and protein. If nitrogen is applied but potassium not, tobacco grows well with the later autumn, the decreasing proportion of superior tobacco leaves and their falling values. At the same time, the potassium application conduces to increasing the content of potassium and sugar of tobacco and to improving the nutrient and quality of tobacco obviously.3 The chlorine nutrient and its control of tobacco in ChongqingBy testing the influence of chlorine on tobacco leaves growth, productivity and quality, analyzing the chlorine dynamic changes in soil, it is concluded that: (1) The chlorine content of tobacco leaves rises with the increasing of chlorine application, which is strongly linear or exponential correlation. Under the condition of film-covered, the optimal chlorine content of each part of leaves is of 3.00-4.40 g/kg when the chlorine is applied from 30.0 to 45.0 kg/hm2 in soil. But uncovered, the moderate chlorine content of each part of leaves ranges from 2.10 to 5.00 g/kg, when the chlorine is applied from 45.0 to 60.0 kg/hm2 in soil. When the chlorine is applied less than that of 3O.Okg/hm2 in soil, the chlorine content of leaves is lower than that of 3.00 g/kg under the above two conditions. According to the chlorine content of leaves, the treatment of C\ application with 45.0kg/hm2 in soil is optimal. The chlorine content in different parts of leaves characterizes the order of upper>middle>lower. The content of S decreases and the content of Ca, Mg, Fe, Mn, Cu and Zn of leaves increases with the application of chlorine fertilizer. (2) The optimal application content of chlorine is 45.0 kg/hm2, when the growth status, yield, value and the proportion of first class leaves of tobacco are better. The yield of leaves and the proportion and value of first class leaves rises with the increasing of chlorine application when it is lower than 45.0 kg/hm2, and there is a decreasing trend of them as content of chlorine is more than 60.0kg/hm2. (3) The content of total sugars and reductive sugars in the tobacco leaves is increased by application of proper chlorine, at the same time, the content of nicotine and total nitrogen of upper and lower leaves are decreased, but the middle leaves are influenced little. (4) The residues of chlorine of all treatments in the soil after tobacco harvest are lower than 30 mg/kg. In this condition, tobacco is plantedproperly. The residues of chlorine and its dynamic changes are subjected to the rainfall and its intensity.4 The boron nutrient and control technique of tobacco in ChongqingThe paper analyzed Space distribution of boron nutrient in main area where tobacco was produced with statistic means, and studied the effect of boron on tobacco growth, nutrient absorbing, and fertilization. (1) H3BO3 is main form of boron in soil of tobacco-planted area in Chongqing. Boron is lack in soil because the form isn't easily absorbed, but easily dissolved and filtered. Content of available boron in soil has a certain relation with parent material and soil type. Content of available boron in different soils was sequenced as: Purple soil> yellow soil > yellow-brown soil. (2) Effect of boron on distribution and content of N, P and K in different organs of tobacco. When boron concentration was low (B S 0.50mg/L), content of N and P in different tobacco organs was sequenced as: Root >leaf>stem. When boron concentration was high (B = 2.00mg/L), content of N and P in different tobacco organs was sequenced as: Leaf > root >stem. Whether boron concentration is low or high, content of K in different organs was sequenced as: Leaf>root>stem. Content of N in root and stem decreased with increase of boron concentration, and in leaves increased with increase of boron concentration. With increase of...
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