Effects Of Water-retaining Agent On Tobacco-growing Soil And Yield-Quality Of Flue-cured Tobacco In Xiangyun

In this study,single factor experiment with random block design was conducted and tobacco variety "Honghuadajinyuan" was served as the experimental material to study effects of four different water-retaining agent levels(T1:180kg/hm2;T2:270kg/hm2;T3:360kg/hm2;CK:No water-retaining agent)on tobacco-growing soil and yield-Quality of flue-cured tobacco in Xiangyun.In order to provide theoretical basis for drought resistant cultivation of flue-cured tobacco in Xiangyun,the indices analyzed are as follows:agronomical character,main growth period,dry matter accumulation,economic traits,chemical components as well as their appropriateness,physic-chemical properties of tobacco-planting soil,soil enzymes’ activity,biomass of cultivable microbe and functional diversity of microbe for tobacco rhizosphere.The results are as follows:(1)Compared with CK,applying water-retaining agent can increase pH value of tobacco-growing soil,biomass of cultivable microbe in rhizosphere and carbon source utilization rate of rhizosphere microbe of flue-cured tobacco.T2(270kg/hm2)can not only ensure pH value of tobacco-growing soil in a proper range,but also enhance the activity of invertase,peroxidase,polyphenol oxidase,dehydrogenase in soil significantly and promote carbon source utilization of rhizosphere microbe which live on carboxylic acid,polymer,carbohydrate,phenolic acid,amino acid,amide.(2)Compared with CK,applying water-retaining agent can promote growth and development of tobacco,increase agonomical performance such as plant hight,effective leaves,maxium leaf length and width in their whole growth period.T2(270kg/hm2)can shorten growth period of flue-cured tobacco with 5.2 days,averagely.Compared with CK,the dry matter accumulation of flue-cured tobacco which were applied water-retaining agent was increased.After transplanting 35,55 and 75 days,the dry weight of aerial part of flue-cured tobacco under treatment T2(270kg/hm2)is increased by 85.95%,52.28%and 21.32%,respectively.(3)Compared with CK,applying water-retaining agent can decrease the level of total nitogen,nicotine,chlorine,and oppositely,increase the level of reducing sugar and potassium,in tobacco leaves.Mmeanwhile,the total sugar level of lower and middle stack position tobacco leaves has been increased.Consequently,the chemical components of tobacco leaves are more appropriate and smoking quality of tobacco leaves has been improved.In this experiment,tobacco leaves under T2(270kg/hm2)showed higher K/Cl with ratio of total sugar and nicotine,ratio of reducing sugar and nicotine,ratio of nitogen and nicotine more appropriate.Compared with CK,applying water-retaining agent can improve the economic traits of flue-cured tobacco.T2(270kg/hm2)can increase yield,prodctive value,average price,ratio of high grade tobacco,level index and production index by 9.72%,23.48%,12.54%,27.57%,11.94%and 23.48%,respectively.