Study On The Characteristics Of Soil Nutrients Supply And Nutrients Uptakes Of Cigar Tobacco In Danjiangkou

Cigar has emerged as a promising contender in the tobacco market because of the rapid development of the national economy and the growing number of consumers.However,the overall quality of domestic cigar tobacco is lower compared to high-quality foreign cigar tobacco.Scientific fertilization is an effective way to increase cigar tobacco quality and yield.The coordinated supply of nutrients has been demonstrated that not only can improve fertilizer utilization,but also enhance photosynthetic efficiency,dry matter accumulation,the intrinsic chemical composition of tobacco leaves,appearance,and sensory quality.The production of cigar tobacco in China,however,is still in early stages and lacks a perfect supporting nutrient management strategy.Therefore,studies on the nutrient supply and nutrient uptake characteristics of cigar tobacco are important to guide the scientific fertilization for producing the high-quality and high-yield cigar tobacco.This study investigated the soil nutrient supply and spatial distribution characteristics of Danjiangkou tobacco planting through soil survey and sampling,using GPS,GIS and geostatistical models.Two varieties,Chuxue 26（CX-26）and Chuxue 14（CX-14）,were planted field experiments to explore the dry matter accumulation and nutrient uptake laws of cigar tobacco.The results of this study can provide a theoretical basis for reasonable fertilization of cigar tobacco.The major findings are as follows:（1）Danjiangkou cigar growing area has potential deficiency of total nitrogen,effective magnesium,effective boron and effective molybdenum,abundance of effective potassium,effective calcium,effective iron and effective manganese,with spatial distribution characteristics of high in the east and low in the west,low in the south and high in the north.The average contents of total soil nitrogen,effective phosphorus and effective potassium were 0.96 g/kg,14.6 mg/kg and 199.7 mg/kg,respectively.The average contents of soil effective calcium,effective magnesium and effective sulfur were 4122.3 mg/kg,175.0mg/kg and 24.4 mg/kg,respectively.The average soil contents of effective iron,effective manganese,effective boron,effective zinc,effective molybdenum,effective copper and water-soluble chloride were 24.9 mg/kg,21.1 mg/kg,0.27 mg/kg,0.88 mg/kg,0.19 mg/kg,1.25 mg/kg and 20.2 mg/kg,respectively.Organic content of soil averaged 14.5 g/kg,with83.1%have the proportion of≤20.0 g/kg.Soil p H averaged 7.10,and the percentage of6.60 to 7.50 was 55.5%.（2）Dry matter accumulation in cigar tobacco plants exhibited in three stages:gradual growth（0-41 d after transplanting）,rapid growth（41-60 d after transplanting）and slow growth（60-85 d after transplanting）.The proportions of dry matter accumulation in CX-26and CX-14 tobacco plants in the gradual,rapid growth and slow growth stages to the total dry matter accumulation ranged from 20.2%to 21.1%,55.6%to 58.1%and 20.9%to 24.3%,respectively.CX-26 dry matter accumulated rapidly at 41-64 d after transplanting,with a maximum rate of 119.5 kg/（hm²·d）.CX-14 dry matter accumulated rapidly at 41-53 d after transplanting,with a maximum accumulation rate of 190.5 kg/（hm²·d）.Throughout the reproductive period,the above-ground stem and leaves dry matter accumulation of CX-26was 1551 kg/hm² and 2517 kg/hm²,respectively,with the tobacco harvest index 0.62.CX-14 accumulated 1403 kg/hm² and 2624 kg/hm² of above-ground stem and leaves dry matter,respectively,with the tobacco harvest index 0.65.（3）The uptake of different nutrients in cigar plants followed the Logistic curve,showing a trend of slow,rapid and then slow change.During the rapid uptake period,CX-26 and CX-14 accumulation of different nutrients accounted for 54.7%to 62.1%and 53.9%to 62.6%of the total nutrients accumulated,respectively.The rapid uptake periods for the major elements N,P and K were at 38-48 d,37-50 d and 38-51 d after transplanting,respectively.The rapid uptake periods for the medium elements Ca,Mg and S were at 39-58 d,36-56 d and 39-50 d after transplanting,respectively.The trace elements Fe,Mn,B,Zn and Cu showed a rapid uptake period at 35-50 d,38-52 d,41-63 d,36-55 d and 37-55 d after transplanting,respectively.The nutrients uptake in CX-26 leaves accounted for63.9%-86.5%of the total aboveground nutrient accumulation of the tobacco plant,and the nutrient harvest index was 0.64-0.87;CX-14 leaves accounted for 61.0%-88.3%of the total aboveground nutrients accumulation of the tobacco plant,while the nutrient harvest index was 0.61-0.88.In summary,producing 100 kg of cigar tobacco requires the uptake of the major elements N,P₂O₅ and K₂O at an average of 3.06 kg,0.64 kg and 5.60 kg,respectively.For medium elements Ca,Mg and S,the average uptake is 3.20 kg,0.61 kg and 0.59 kg,respectively.For the trace elements Fe,Mn,B,Zn and Cu,the average uptake is 59.0 g,21.8 g,4.0 g,4.0 g and 1.6 g,respectively.To achieve this,it is necessary to consider the soil nutrients supply status and the target yield of tobacco plant for scientific fertilization.