Effects Of Cropping System And Fertilization On Flue-cured Tobacco And Tobacco-grown Soil

Zunyi is one of the main areas for production of good quality flue-cured tobacco in China.Continuous cropping and sole chemical fertilizer application in tobacco cultiva tio n resulted in a series of problems,including soil structure damage,fertility deterioratio n,frequent disease occurance,plant growth retard,and tobacco quality and yield decline,which adaversly influence the sustainable development of flue-cured tobacco production and need to be solved urgently.Proper crop rotation and organic manure application are effective to improve soil structure,fertility,and micro ecological environment,to promote crop growth and development,and to increase crop yield and quality.A long-term field experiment was established to realize the influence of cropping modes(monotobacco cultivation and tobacco-corn rotation)and fertilization(o nly chemical fertilizers and chemimal ferlizer in combination with organic manures)on the growth and quality of flue-cured tobacco,the physical and chemical properties of soil,soil bacteria and soil bacteria community.This study is expected to provide a theoretical basis for improving the productivity of tobacco fields in Zunyi,maintaining a healthy soil environment and realizing the sustainable utilization of tobacco.Key research findings are as follows:1)Tobacco-corn rotation and combined application of organic fertilizer significa ntly affected the growth,yield and quality of flue-cured tobacco and chemical compositio n.Compared with continuous tobacco cropping and only chemical fertilizer applicatio n(CCF),corn-tobacco rotation in combination with chemical ferlitizr plus organic manures(RCFM)significantly increased tobacco seedling height,stem diameter,maximum leaf area,and leaf yield and economical income,and synchronize chemica l components in tobacco leaves.2)Tobacco-corn rotation significantly reduced the disease of flue-cured tobacco.Compared with continuous tobacco cropping,the incidence and disease index of mosaic were reduced by 45.8% and 56.0%,and bacterial wilt by 56.1% and 50.0%,respectively,in corn-tobacco rotation treatment.3)Tobacco-corn rotation and combined application of organic fertilizer significa ntly improved soil structure and aeration conditions..RCFM decreased the soil bulk density by 15.7%,whilist the porosity was increased by 13.4% in comparation with only chemica l fertilizer treatment.Compared with the initial soil,continuous tobacco cropping significantly reduced the soil pH in cultivation,but there was no significant change in soil pH in organic fertilizer treatment.4)Tobacco-corn rotation significantly affected the number and biomass of microorganisms in tobacco growing soil.Microbial biomass carbon and nitrogen,biomass carbon/nitrogen ratio,and the number of fungi decreased significantly in the soil with continuous tobacco cropping compared with corm-tobacco rotation.5)Both Venn and principal component analysises showed that cropping system affected tremendously bacterial diversity,and fertilization fungal diversity.The bacterial richness,evenness and diversity in the soil with crorn-tobacco rotation were significa nt ly higher than the continuous.However,fungal richness,evenness and diversity behaved otherwise.6)In the bacterial composition,Proteobacteria,Actinomyces,Chloroflexi and Acidobacteria are the dominant phylum in tobacco-planting soils.The relative abundance of Proteobacteria in rotation soil is significantly higher than that in continuous cropping,and the relative abundance of Chloroflexi and Acidobacteria are lower than continuo us cropping.As to fungi composition,Ascomycota,Basidiomycota and Zygomycota are dominant phylum,in which the relative abundance of Ascomycota is higher in continuo us cropping,and the Basidiomycota is higher in rotation soil.Therefore,RCFM was able to promote tobacco plant growth,increase the tobacco leaf quality,harmonize the chemical composition in tobacco leaves,and improve the physical and chemical environment and biological activity of tobacco-grown soil.It is a positive effect on improving the productivity of tobacco soil,maintaining the health and sustainable utilization of tobacco soil,and is a kind of cultivation combined with fertilization.This model is worth popularizing in the Zunyi tobacco area...