Study On Composition Of Soil Aggregates And Biological Characteristics Of Suppressive And Conducive Soils Of Continuous Cropping Bananas In Hainan

Banana fusarium wilt disease,also called the panama disease,is one of the devastating soil-borne pathogens of banana vascular bundle necrosis is infected by Fusarium oxysporum f.sp.Cubense race 4.In recent years,banana fusarium wilt disease serious damage to the development of banana plantations.Suppressive soils and conducive soils were collected from Hainan Lingao(silt loam)and Hainan Ledong(sandy loam)garden.To explore the formation mechanism of suppressive soils of banana,the differences of soil physical and chemical properties and microbial community structure of two types of soils were studied.Through soil culture and pot experiments by adding functional microorganisms,the promoting growth of banana with cultivating healthy soils was investigated.The main results were as follows:1.It was found that there were significant differences in the physical and chemical properties of suppressive soils and conducive soils.Compared to the conducive soils,mean values of total carbon and total nitrogen were significant higher in suppressive soils,while soil pH was lower;the content of Ca was significant higher in suppressive soils of brick red soils;the composition of the macro-aggregates were significant higher in suppressive soils,in the>2 mm aggregates,the percentage of ST and SD was 1.87 and 2.38 times in suppressive soils than those of conducive soils,the results were determined by particle size distribution of soil aggregates(0-0.25 mm and 0.25-2 mm),there were more large particle sizes in suppressive soils than conducive soils;soil enzyme activities were significant higher in suppressive soils of soil invertase activity,urease activity,neutral phosphatase activity and catalase activity,were higher about 20%-200%.2.Comparison of microbial community structure differences in soil aggregates of banana suppressive and conducive soils.It was found that there were no broad variations in the bacterial abundance and fungal abundance,but the abundance of Fusarium oxysporum of the suppressive soils were higher than that conducive soils.At the diversity of mcrobial communities structure,the flora diversity index of Shannon value has a significant rule in the bacteria communities and fungal communities.The bacterial diversity showed that the Shannon values of the suppressive soils were higher than those of the conducive soil,while the fungi had the same rule except for the<0.053 mm diameter.The results of PCoA showed that the bacteria communities and fungal communities of all the soils were separated along the first axis,while those within different soil aggregates were not notably separated.In particular,the community structures of the suppressive soils were separated from these of the conductive soils in the fungal community.The relative abundance of microbial community,At the relative abundance of bacteria,in the>0.053 mm sized fractions,the relative abundances of the top five phyla(Acidobacteria,Actinobacteria,Bacteroidetes,Firmicutes and Proteobacteria)made up 70%of the total bacterial sequences,Bacteroides was the dominant phyla in the<0.053 mm sized fractions(>40%),In addition,the Bacteroidetes relative abundances in the suppressive soils were higher than those in the conducive soils;At the relative abundance of bacteria,The relative abundances of Basidiomycota in the macro-aggregates(>0.25 mm)of the suppressive soils were significantly higher than those in the conducive soils.However,the relative Ascomycota abundances in the different particle size of the conductive soils were almost all higher than those in suppressive soils.At the level of genera in>0.25 mm aggregates,the relative abundance of Pseudomonas,Streptomyces and Trichoderma in suppressive soil was higher than that of coducive soil.3.The soil culture experiment was carried out in sandy soil of Hainan Ledong banana garden.The results showed that BOF treatment significantly increased mean values of total carbon and total nitrogen,which was 32.76%,8.58%higher than that in the control.The content of the macro-aggregate of BOF treatment significantly increased,which was 2.35 times that of the control.Soil enzyme(invertase,urease,neutral phosphatase and catalase)activities were significantly increased by 13.87%-47.85%with BOF treatment,and the number of Fusarium was significantly decreased with BOF treatment.But the soil total carbon,total nitrogen,soil enzyme activities and microbial population were decreased with the increase of culture time.The results of pot experiments showed that the soil treated with BOF significantly promoted the growth of bananas,the fresh weight of banana plants was 2.15 times that of the control.