| Objective To explore whether silkworm excrement fermentation fertilizer could alleviate the continuous cropping obstacle of A.macrocephala and the micro ecological mechanism to alleviate the continuous cropping obstacle,we detected the active ingredient content of A.macrocephala in different treatments and detected the microbial structure in silkworm excrement fermentation fertilizer and rhizosphere soils in different treatments.Methods 1.Three groups were arrayed.The first group of A.macrocephala have been monocultured for 3 years(2009-2011);The second group have been cultivated for 2 years(2010-2011);The third one have been planted just for 1 year(2011).Soil samples were taken in autumn 2011 from the rhizosphere and bulk soil of A.macrocephala.Rhizosphere soil of dying plants were also collected.Detect the physicochemical properties and microbial structure of Rhizosphere soil and bulk soil.2.Six treatments were arrayed which composed of continuous-cropping group,rotation-cropping group,high-dose of fermented fertilizer group,low-dose of fermented fertilizer group,high-dose of unfermented fertilizer group and low-dose of unfermented fertilizer group.Survival rate and plant height were detected at different growth period.Yields of different treatment groups were calculated at the harvesting time.Detect the content of atractylenolide Ⅰ and Ⅲ of different treatment groups by HPLC and analyze the mitigation effect of silkworm excrement fermented fertilizer on cropping obstacles.3.Collect soil and silkworm excrement before fermentation,and collect the fertilizer fermented for 30 days and 90 days after fermantation.Detect the bacteria community structure by high-throughput sequencing to analys the difference between fermented fertilizer,soil and silkworm excrement.4.Detect the bacteria and fungi community structure of rhizosphere soil of continuous-cropping group,rotation-cropping group,high-dose of fermented fertilizer group,low-dose of fermented fertilizer group,high-dose of unfermented fertilizer group and low-dose of unfermented fertilizer group.Analyze the changes of microbial structure among different treatments to clarify the microecosystem mechanism of silkworm excrement fermented fertilizer to alleviate continuous cropping obstacle.Results 1.In comparison to the rhizosphere soil of dead plants,the one of livings showed lower level of pH,phosphatase activity but higher level of organic matter content.With the increase of monocultured year,the pH of soil of A.macrocephala was obviously increased,while the phosphatase activity increased first and then decreased at the third year.However,the content of organic matter changed little,ranging from 2.5 to 2.66%.The diversity and abundance of bacteria in dead plants were higher than that of living plants,while the diversity and abundance of fungi were higher in living plants.The richness of some bacterium such as Sphingobium,Hyphomicrobium,Novosphingobium,Burkholderia,Nitrobacter were decreased in dead plants,and these bacterium were closely related to the health of plants.The abundance of bacterium such as Asticcacaulis,Rhizomicrobium,Cupriavidus,Ralstonia,Sorangium,Pseudoxanthomonas,Sinobacteraceae,Ktedonobacterales,Acidobacteriaceae,Gemmatimonadaceae were increased in dead plants,and these bacterium were related to the death of plants.2.Continuous cropping resulted in a diminished output and survival rate while application of unfermented fertilizer showed no improvement in yield.On the other hand,the yield in rotation cropping group,high-dose and low-dose of fermented fertilizer groups exceed 10.69,10.41 and 4.83 times that of continuous cropping group,respectively,which showed that application of fermented fertilizer could effectively remit replant disease.Furthermore,among all groups the content of atractylenolide I was the highest level(0.5570 mg·g-1)in high-dose fermented fertilizer group,while that of atractylenolide III was the highest level(0.0867 mg·g-1)in low-dose unfermented fertilizer group and all group showed higher content of active ingredients than that of continuous cropping group.3.The number of OTU in soil,silkworm excrement,fermented fertilizer A and fermented fertilizer B were 3267,1187,3637 and 1835 respectively.The diversity index in fermented fertilizer and soil were higher than any others,and the diversity index in silkworm excrement was the lowest.The dominant phylum wereBacteroidetes,Proteobacteria,Actinobacteria,Acidobacteria,Cyanobacteria,TM7,Planctomycetes and Verrucomicrobia.The dominant genus were Parapedobacter,Sphingobacterium,Ochrobactrum,Flavobacterium,Devosia,Subdivision3_genera_incertae_sedis,Bacillus and Brucella.Parapedobacter,Sphingobacterium,Flavobacterium and Devosia were detected both in silkworm excrement and fermented fertilizer which indicated that these bacterium in fermented fertilizer came from silkworm excrement instead of soil.And the result of cluster showed that there was no significant change in fermented fertilizer A and fermented fertilizer B,which indicated that the microbialstructure in fermented fertilizer was stable.4.The OTU number of bacteria in continuous-cropping group,rotation-cropping group,high-dose of fermented fertilizer group,low-dose of fermented fertilizer group,high-dose of unfermented fertilizer group and low-dose of unfermented fertilizer group were 3467,3594,3872,4537,4638 and 6640 respectively.Diversity index in continuous-cropping group were the lowest.The dominant genus wereGp1,Gp2,Burkholderia,Gp3,Subdivision3_genera_incertae_sedis,Rhizomicrobium,Phenylobacterium,Gemmatimonas,Sphingomonas,Bradyrhizobium,Aciditerrimonasand Thermoleophilum,but the abundance of these dominant bacterium were differ from different treatments.The abundance of harmful bacterium in continuous-cropping group was higher than other treatments.The OTU number of fungi in continuous-cropping group,rotation-cropping group,high-dose of fermented fertilizer group,low-dose of fermented fertilizer group,high-dose of unfermented fertilizer group and low-dose of unfermented fertilizer group were 1051,1352,1648,2358,1756 and 1609 respectively.The diversity index of fungi in continuous-cropping group was the lowest too,and the diversity of fungi was lower than that of bacteria.There were more harmful bacteria such as Penicillium in continuous-cropping group and more beneficial bacteria in silkworm excrement fermented fertilizer group such as Meyerozyma.Six kinds of treatment mainly affected the abundance of microbial in soil,and the fungi was more sensitive than bacteria to these treatments.Conclusion The microbial structure of rhizosphere soil was significantly changed after continuous cropping.The application of silkworm excrement fermented fertilizer could alleviate the continuous cropping obstacle of A.macrocephala by improving yieldand active ingredient content,while the unfermented fertilizer couldn’t alleviate the continuous cropping obstacle.One of the reason that silkworm excrement fermented fertilizer could alleviate the continuous cropping obstacle was that the microbial structure in fermented fertilizer had changed after fermentation.The content of beneficial bacterium such as Parapedobacter,Sphingobacterium and Devosia were increased in fermented fertilizer.And some other bacterium which was related to the health of plants were detected only in fermented fertilizer.Besides,the application of fermented fertilizer changed the microbial structure in rhizosphere soil.It increased the content of beneficial bacterium such as Dyella,Devosia and Flavobacterium,which were also existed in fermented fertilizer. |
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