Effect Of Tobacco Stalk-derived Biochar On Soil Microbes And Greenhouse Gases Emission In The Tobacco-rice Rotation Field

In order to achieve the effective use of waste recycling in the production of tobacco,to better understand the effect of biochar(derived from tobacco stalk)on soil ecology in the tobacco-rice rotation field,the biochar was applied at levels of 0,10,40,and 80 t/hm2 in randomized block design.The effects of the biochar on microbes and emission of greenhouse gases were also investigated.There are two main points about this experiment:collected the rhizosphere soils and further test using high throughput sequencing of 16S amplicons,also,tested the physical and chemical properties,which were to studied the effects of the biochar on microbes;The laws of annual changes of greenhouse gases on the field were investigated by closed static chamber method.At the same time,collected the rhizosphere and non-rhizosphere soil in the four growing period of crop and tested the related bacteria using qPCR.The effects of the biochar on greenhouse gases emission and related bacteria in tobacco-rice rotation field were studied by this process.The result shows that with the application of tobacco stalk-derived biochar the operational taxonomic unit(OUT,97%similarity)and chaol index were increased in rhizosphere soil of tobacco field at the level higher than 10 t/hm2.The OUT increased by 26.4%.The highest distribution was observed in Proteobacteria and Acidobacteria that totally accounted for 66.16%to 74.50%of the total bacteria.The increase of Proteobacteria,Acidobacteria,Verrucomicrobia,and Bacteroidetes and decrease of Gemmatimonadetes,Chloroflexi,Nitrospira,and Planctomycetes were positively associated with the application of biochar.This association was also applied to the increase of plant growth-promoting microorganisms(PGPMs).The result of rhizosphere soil of paddy field shows that the OUT and chaol index were decreased,but,Shannon index increased.The highest distribution was observed in Proteobacteria and Acidobacteria that is the same to tobacco field.The increase of Proteobacteria,Actinobacteria and Firmicutes and decrease of Acidobacteria and Verrucomicrobia were positively associated with the application of biochar.The response mechanism of Actinobacteria was totally opposite in contrast with the tobacco field at the taxon level of class.It observed that the plant growth-promoting microorganisms were also increased,therefore,were different to the tobacco field.The results of physical and chemical properties of rhizosphere soil shows that the different between tobacco and paddy field were the change of alkali-hydrolyzable nitrogen.It was decreased in tobacco field at higher level while increased in paddy field.In addition,the soil organic matter,total nitrogen and available potassium were observed to increase after the application in both field.The N2O emissions from tobacco field with higher levels of application(40.80 t/hm2)was decreased.It were reduced by 7.70%,10.05%respectively.But in lower application(10 t/hm2),it was increase by 0.96%.The result of qPCR shows that the copies of amoA gene of denitrifying bacteria have different variation in four period.In the three periods of seedling stage,rosette stage and rapid growth stage,the copies are gradually growing,and then declined in maturity.However,amoA and cnorB gene copies are no significant correlation with N2O emission.The application of biochar can significantly reduce the emission of CH4,and with the higher level of application,the emission become lower gradually.It decreased 26.29%,34.77%and 39.22%respectively.The CH4 emission was significantly decreased with the increasing of the copies of PmoA gene of methanotrophic bacterial in non-rhizosphere soil,and so is the copies of 16S rDNA gene of methanogenic archaeal in rhizosphere and non-rhizosphere soil.In the maturity period of rice,the emission of CH4 was the lowest while the copies of methanogenic archaeal and methanotrophic bacterial were the highest.The copies of 16S rDNA of methanogenic archaeal tends to decrease in the sum of the whole rice growing season after application of biochar.In conclusion,the soil fertility,the diversity of soil microbe,and the abundance of PGPMs were totally influenced by the application of tobacco stalk-derived biochar.It increasing the soil fertility and the diversity of soil microbe of tobacco field while decreasing the diversity of soil microbe of paddy field.The abundance of PGPMs were all increasing in the field.The application of biochar can reduce the emission of greenhouse gases in tobacco-rice rotation field.What is more,the reducing emission of CH4 was related to the decreasing of methanogenic archaeal after application.