Mechanism Analysis Of The Influences On Flue-cured Tobacco Soil Health Of Different Previous Crops And Exploration Of Soil Health Remediation Technology

Currently, flue-cured tobacco continuous cropping obstacles is increasinglyprominent, that is serious diseases and the decline of yield and quality, whichseriously hindered the development of flue-cured tobacco industry in China. Croprotation is an effective way to solve the problem of continuous cropping, however, itis hard to apply as choosing a reasonable crop sequence is difficult. Various confusionneeds to be solved. As the gradually understanding of the ecosystem, the research ofcontinuous cropping and crop rotation differences from soil micro-ecological will bedeveloped quickly. The comprehensive understanding of soil micro-ecologicalprovides the theory basis for the development of continuous cropping, which will nolonger rely on crop rotation.In this study, the bacterial and nitrogen transformation bacteria population,theenzyme activity and the content of organic carbon and the relationship between thembefore tobacco planting was explored. The16SrDNA, amoA gene and communitydiversity is analysis respectively to the preceding corp sweet potato, rape, hot pepper,tobacco and maize. At the same time, fertilization technology strategy for differentpreceding crops was discussed. The field experiment, the recovery effect of differentbiological carbon content and dosage form for continuous cropping soil health oftobacco, is also completed, with the analysis of the tobacco growth in differentenvironment，resistance and soil health key parameters and bacterial communitydiversity. The main results were as follows:（1）The bacteria common count，organic carbon content and enzyme activity ofdifferent five continuous crop were analysis.The order of soil bacteria populationsweet potato>rape>chilli>corn>tobacco, and organic carbon content is same. Theorganic carbon content of sweet potato, chilli and rape reach the requirements of highquality tobacco production. The soil enzyme activity, organic carbon content andbacteria population of different continuous crop has positive correlation. The enzymeactivity of sweet potato, chilli, rape is higher than that of tobacco and corn. The Soil nitrifying bacteria population of soil, whose continuous crop is tobacco,is the biggest. The nitrogen-containing compound can translate into nitrite nitrogen,which can be easily absorbed by green plants. This may be the reason why sweetpotato is helpful for tobacco growing. Chill as previous crop, can strengthen soilammoniation, and indirectly stimulate the transformation of nitrate nitrogen. Otherprevious crops has little effect on ammonifying bacteria.The nitrogen-fixing bacteriais more in the field, whose previous crop is maize. The maize can absorb morenutrient with the help of nitrogen-fixing bacteria, at the same time, the process canalso stimulate and enhance the ability of the soil nitrogen-fixing bacteria. Tobacco canenhance the release nitrogen ability of soil and the ability of denitrifying bacteria.（2）Three kinds of diversity index, Shannon, Simpson and McIntosh, are usedfor the analysis of soil total bacterial colonies distribution.The results show that compared with tobacco, the soil microbial community insweet potato is the most abundant. The rape has a restrain for the original advantagebacteria, and a promotion for other groups.Chill as previous crop,can enrich thecommon species in soil, which are suitable for chill growth. And they reduce theoriginal predominant bacteria in soil. Maize as previous crop, the change of bacteriadistribution in soil is not obvious. The PCR-DGGE of ammonia oxidizing bacteriashow that the order of diversity index is:sweet potato>rape>corn>chilli>tobacco,which is consistent with bacteria DGGE.（3）According to the analysis result of Different crop soil micro-ecological, inorder to make soil more health,for tobacco field, whose previous sweet potato, an addchemical fertilizer is better. While for corn and tobacco, organic fertilizer is needed,and for chill and rape, Balanced fertilization is necessary.（4）Field experiments are taken by adding add biomass carbon fertilizer foradjusting the soil C/N ratio, in order to repair the soil health.The results show that inthe whole growth of flue-cured tobacco, the bacterial population, enzyme activity,andsoil organic carbon content were higher in ecological carbon fertilizer added soil thanCK(without any ecological carbon fertilizer added),and with the increase of carboncontent, soil micro ecological index also increase accordingly. In the birth period, theorganic carbon content of CK gradually decreased, but no significant difference (P <0.05), and the activity of invertase, amylase, cellulose enzyme show differentvariation trend, decrease-increase, increase-decrease, increase-decrease respectively.Only the change of invertase has significant difference (P <0.05). From the view of Flue-cured tobacco biology and resistance, the height, leafnumber and black shank disease control effect of different processing after60dgrowing. The results show that with the increase of biomass carbon content, theheight and leaf number increased as well. Meanwhile, the resistance is enhanced.The analysis of bacterial colony diversity show that in the whole reproductiveperiod, when the ecosystem carbon fertilizer is added, the amount and diversity ofbacteria quantity and ammonia oxidizing bacteria is more than CK, and showed atrend of increasing. With the increase of organic carbon content, the number anddiversity of bacteria increased too. CH-25(high biomass carbon content) showed thebest result.M-20(high organic carbon content) showed the richest diversity. And itmay be related to acid contained by M-20. Overall, the increase of C/N in soil canimprove the diversity of bacterial and ammonia oxidizing bacteria in flue-curedtobacco.