| Soil is an important part of agricultural ecosystem and also the material basis of agricultural production.Sustainable use of soil is a key concern in agricultural production.How to effectively delay the decline of soil quality,improve soil physicochemical property and biological properties,and promote crop to achieve high yield and stable quality are the problem to be solved in agricultural production at present.Taking the typical tobacco-rice rotation farmland in Chenzhou as the research object,by multi-site collection of soil and tobacco samples and adopting multivariate statistical methods such as detrended correspondence analysis,constrained ordination analysis and partial least squares path model construction,this study explored the differences of soil physicochemical property,bacterial,carbon and nitrogen cycle functional microbial communities and flue-cured tobacco yield and quality in different tobacco-rice rotation years,and analyzed the effects of soil physicochemical property,bacterial and nitrogen cycle functional microbial communities on flue-cured tobacco yield and quality.The following results were obtained:1.The differences of soil physicochemical property in different tobacco-rice rotation years were analyzed.The results showed that compared with rice monoculture(CK),tobacco-rice rotation significantly increased soil p H and organic carbon content,and significantly decreased nitrate nitrogen content.As the tobacco rice rotation period reaches more than 40 years,the nitrate nitrogen content increases significantly,and the soil p H value tends to stabilize and is greater than 7.50.2.The differences of physical characteristics,chemical composition,sensory quality and economic traits of flue-cured tobacco in different tobacco-rice rotation years were analyzed.The results showed that with the increase of rotation year,the style highlighting degree,aroma quality,aroma content,permeability,smoke softness,fineness,offensive odor,tobacco irritation,aftertaste and sweetness of the middle leaves were decreased to a certain extent,but the smoke concentration in the upper leaves was increased,and it had no effect on the strength of the middle and upper leaves,the irritation in the upper leaves and the dryness in the middle leaves.The physical indexes such as leaf length,leaf width and single leaf weight in the upper and middle leaves of the rotation tended to decrease with the increase of rotation years.The total sugar content of upper leaves was significantly increased,while the total sugar and reducing sugar content of middle leaves was significantly decreased,while the nicotine content showed an increasing trend,and the total sugar and reducing sugar content of lower leaves was decreased.The economic traits of flue-cured tobacco decreased with the rotation years,but the yield and output value had no significant difference.the yield of flue-cured tobacco in the farmland with tobacco-rice rotation for more than 40 years decreased by 1.43%,the output value decreased by 5.13%,and the average price decreased by 3.70% as compared with the farmland with 10～20 years.3.The differences of soil bacterial community structure and diversity in different tobacco-rice rotation years were analyzed.The results showed that the soil bacterial community in different tobacco-rice rotation years was composed of dominant species such as Proteobacteria,Acidobacteria,Chloroflexi,Gemmatimonadetes,Bacteroidetes and Actinomyces.Tobacco-rice rotation significantly increased the abundance index of soil bacterial communities in 2020 and changed the structure and diversity of bacterial communities.Rotation duration had little effect on bacterial community,and there was no regular succession of bacterial community.4.The differences of community structure and diversity of nitrogen fixing bacteria,ammonia oxidizing bacteria and denitrifying bacteria in different tobacco-rice rotation years were analyzed.The results showed that tobacco-rice rotation significantly increased the abundance of Mesorhizobium,Frankia,Pseudomonas and rhizobium in nitrogen-fixing bacterial community,and the abundance of Nitrosospira and Cupriavidus in ammonia-oxidizing bacterial community.Tobacco-rice rotation significantly increase that abundance index and diversity index of the ammonia-oxidizing bacteria community and changed the community structure of soil nitrogen-fixing bacteria,ammonia-oxidizing bacteria and denitrifying bacteria.The rotation years had a certain effect on the community structure of nitrogen-fixing bacteria,but no significant effect on the community structure of ammonia oxidizing bacteria and denitrifying bacteria.5.The differences of community structure and diversity of soil methane-oxidizing bacteria and methanogenic bacteria in different tobacco-rice rotation years were analyzed.The result showed that tobacco-rice rotation significantly increase that abundance of Nitrosococcus in the methane-oxidizing bacteria community and the abundance of methanogenic bacteria Methanobacterium.With the prolongation of rotation,the abundance of methanogenic microflora Methanocorpusculum decreased significantly and that of Methanobacterium increased significantly.Tobacco-rice rotation significantly increased the abundance and diversity index of methane-oxidizing bacteria community,while the abundance and diversity index of methanogenic bacteria community in tobacco-rice rotation for 20–40 years was the lowest,which was significantly different from other treatments.Tobacco-rice rotation changed the community structure of soil methane-oxidizing bacteria and methanogenic bacteria,while different rotation years had some influence on the community structure of methanogenic bacteria but no significant influence on the community structure of methane-oxidizing bacteria.6.The interactions between yield and quality of flue-cured tobacco and soil physicochemical properties,bacterial and carbon and nitrogen cycle functional microbial communities in different tobacco-rice rotation years were studied.The results showed that soil p H and ammonium nitrogen were environmental factors that significantly affected the bacterial community structure in different tobacco-rice rotation years.Soil p H,organic carbon,nitrate nitrogen and ammonium nitrogen were environmental factors that significantly affected the community structure of soil nitrogen-fixing bacteria,ammonia-oxidizing bacteria and denitrifying bacteria.The results of PLSPM showed that the physicochemical properties of soil,the structure and diversity of nitrogen-fixing bacteria community had a significant positive correlation with the yield and output value of flue-cured tobacco,and the structure and diversity of ammonia oxidizing bacteria community had a significant negative correlation with the yield and output value of flue-cured tobacco.The improvement of soil physicochemical property,nitrogen-fixing bacteria community structure and diversity was beneficial to the increase of flue-cured tobacco yield and output value,while the improvement of ammonia oxidizing bacteria community diversity was not conducive to the production of flue-cured tobacco. |
