Study On Soil Remediation Technology Of Flue-cured Tobacco Continuous Cropping And Its Application Effect

As an important economic crop in China,continuous cropping obstacle has become the main factor limiting the development of flue-cured tobacco.As the representative production area of high-quality tobacco,the continuous cropping problem is particularly prominent in central Henan.Therefore,it is of great significance for the development of tobacco industry to adopt effective technology to repair the continuous cropping soil of flue-cured tobacco.In this study,we first analyzed the correlation between continuous cropping obstacle factors and yield and quality of flue-cured tobacco in 1 year（CK）,3 years（3a）,5 years（5a）and 7 years（7a）,and explored the primary and secondary factors causing continuous cropping obstacle.Secondly,3 years of continuous cropping soil was selected as the remediation object,and the reductive soil disinfestation materials with better remediation effect were selected from different organic materials to regulate the soil micro-ecology.At the same time,all kinds of bactericides were quantified to analyze the mechanism of soil microecological remediation.Furthermore,pot experiments were conducted to study the effects of reductive soil disinfestation（RSD）,scientific fertilization（fertilizer）or RSD plus scientific fertilization application on soil characteristics（nutrient,microecology）and plant growth（agronomic traits,physiological state and chemical quality）in four growth stages of flue-cured tobacco（seedling returning,root extension,vigorous growth and maturity）.Finally,the actual remediation of each repair technology was verified at the field scale.The main results are as follows:（1）Long-term continuous cropping led to the decline of yield and quality of flue-cured tobacco,the lack of soil nutrients and the imbalance of soil microecology.Mantel test analysis showed that the main factors of continuous cropping obstacles in central Henan were bacterial community imbalance（3a:r=0.7841;5a:r=0.9832;7a:r=0.6943）and nutrient imbalance.When the soil was continuous cropped for 7 years,the imbalance of fungal community was also became the main factor（r=-0.6244）.The accumulation of allelochemicals in rhizosphere was not the main factor of continuous cropping obstacle.The imbalance of bacterial community means that with the extension of continuous cropping years,the diversity and richness of the community decreased significantly,while the relative abundance changed significantly.At the phylum level,the relative abundance of Proteobacteria and Bacteroidetes decreased with continuous cropping years.The abundance of Actinobacteria,Chloroflexi,Gemmatimonadetes and Firmicutes increased.The results showed that when the soil was continuous cropped for 3 years,the major elements in soils,especially TC（decreased by22.94%）and TN（decreased by 35.37%）,were missing;when the continuous cropping years exceeded 3 years,besides the major elements,the medium and trace elements（especially Ca,Mg and Fe）were also missing.（2）The indoor soil culture experiment showed that:according to the effect of the RSD using different organic materials on soil micro-ecology,starch was found significantly improved the diversity and richness of bacterial community（ACE and invsimpson index increased by 11.48%and 20.89%）,however,the diversity and richness of fungal community decreased significantly（ACE and invsimpson index decreased by 25.58%and 21.38%）.The abundance of functional bacteria in metabolic phase increased significantly（399.31%）,while the abundance of plant pathogens was significantly reduced（52.68%）.RDA analysis showed that the order of remediation effect of strong reducing soil was H₂S>iron and manganese ions>organic acid>NH₃.（3）Pot experiment showed that:the application of RSD and RSD plus scientific fertilization significantly promoted the content of available nutrients.With the growth of flue-cured tobacco,the available nutrients decreased first,then increased,and then decreased.The results showed that the diversity and richness of micro-ecology under RSD and RSD plus scientific fertilization were significantly higher than those of other treatments.the abundance of metabolic related functional bacteria and endophytic bacteria under reductive soil disinfestation treatment and comprehensive treatment were significantly higher than those of other treatments,and the abundance of cell forming and signal transduction functional bacteria and pathogenic bacteria were significantly lower than those of other treatments.The relative abundance of metabolism related functional bacteria,cell formation and signal transduction functional bacteria,and plant pathogens increased in different degrees in the vigorous growth stage of flue-cured tobacco.As to flue-cured tobacco,RSD plus scientific fertilization significantly improved the agronomic traits（biomass increased by 200.85%）,growth and development（incidence rate decreased by 66.7%）,and chemical compounds accumulation and coordination,which met the standard of high quality tobacco production.RSD basically met the standard of high quality tobacco production.（4）Field experiments further verified that the main factors of continuous cropping obstacle were flue-cured tobacco continuous cropping obstacle in soil and soil nutrient imbalance.Combined treatment（oxidant treatment+RSD+scientific fertilization）had good repair effect on continuous cropping obstacle（biomass increased by 38.54%,incidence rate decreased by 77.8%）.The accumulation of allelochemicals in rhizosphere was not the main factor of continuous cropping obstacle in central Henan according to oxidant treatment;In conclusion,RSD（3%starch aqueous solution）+scientific fertilization treatment(N171.34 kg·hm^-2)can repair the soil micro ecological,improve soil nutrients,improve the growth of tobacco plants,promote the yield and quality of tobacco leaves,which provide scientific guidance and feasible technology for the restoration of continuous cropping obstacles in central Henan.