| The ever increase of greenhouse cultivation area, continuous monocrops and excessive application of chemical fertilizers caused the deterioration of soil quality and soil function, and further resulted in the outbreak of severe soil-borne disease. Serious loss of crop production in the agriculture has been caused by soil-borne disease. Many strategies have been taken to improve soil suppressiveness against soil-borne disease, but limited success has been achieved. However, recently, organic amendments and biocontrol, such as bioorganic fertilizer, as the popular and effective methods to control soil-borne disease have achieved best results. Moreover, nitrogenous amendments, as soil pretreatment, also play an important role in controlling soil-borne disease. In this study, the first part explored the control efficiency of bioorganic fertilizer againstn the tomato Fusarium wilt, strawberry Phytophthora and tomato bacterial wilt through several trials of crops in the field; In the second part, in order to resolve the dispose problem of the compost products from CO2 enrichment technique, we hypothesized the compost products from CO2 enrichment technique could be considered as an organic amendment, to evaluate the control efficiency of the products on tomato bacterial wilt in three trials in the field and demonstrated the relative mechanism of the products for controlling bacterial wilt disease; In the third part, we conducted the soil culture experiments to explore the control efficiency of calcium cyanamide (CC), an ammonium bicarbonate and lime mixture (A+L) and ammonia water (AW) at different nitrogen level against the survival of Ralstonia solanacearum, the pathogen of bacterial wilt disease, and their effect on soil microbial community structure and diversity. The main results in our study are listed as followed:1. Compared with the application of chemical fertilizers and organic fertilizers, the incidences of tomato Fusarium wilt and strawberry Phytophthora in bioorganic fertilizer treatment were the lowest and decreased by 43%-56% and 49-65%, respectively, and the yields of tomato and strawberry increased by 40.2% and 66.7%, respectively. Moreover, application of bioorganic fertilizer improved soil physicochemical properties, increased the nutrients availability, and enhanced the microbial activities and community populations. Therefore, bioorganic fertilizer have the ability to effectively control the tomato Fusarium wilt and strawberry Phytophthora.2. In this study, a novel bioorganic fertilizer revealed a higher suppressive ability against bacterial wilt compared with several soil management methods in the field over five growing seasons from March 2011 to July 2013. The application of the bioorganic fertilizer significantly (P<0.05) reduced disease incidence of tomato and increased fruit yields in four independent trials. The association among the level of disease incidence, soil physicochemical and biological properties was investigated. The soil treated with the bioorganic fertilizer increased soil pH value, electric conductivity, organic carbon, NH4+-N, NO3--N and available K content, microbial activities and microbial biomass carbon content, which were positively related with soil suppressiveness. Bacterial and actinomycete populations assessed using classical plate counts were highest, whereas R. solanacearum and fungal populations were lowest in soil applied with the bioorganic fertilizer. Microbial community diversity and richness were assessed using denaturing gel gradient electrophoresis profile analysis. The soil treated with the bioorganic fertilizer exhibited higher bacterial community diversity but lower fungal community diversity. Redundancy analysis showed that bacterial community diversity and richness negatively related with bacterial wilt suppressiveness, while fungal community richness positively correlated with R. solanacearum population. We concluded that the alteration of soil physicochemical and biological properties in soil treated with the bioorganic fertilizer induced the soil suppressiveness against tomato bacterial wilt.3. In the present study, we used a secondary compost process to re-use the compost products, and evaluated the effect of secondary compost products (SCP) on tomato bacterial wilt in three field trials. The results showed that SCP application had great potential for the control of tomato bacterial wilt. Compared with the control (local conventional cultivation), SCP application decreased the disease incidence by 32-81% and increased fruit yields by 59-95% across the three trials. Irrespective of treatment, significant correlations were found between R. solanacearum populations and total nitrogen, soil organic carbon and NO3--N contents. Moreover, the severity of bacterial wilt negatively associated with the activity of phosphomonoesterase and P-D-glucosidase, FDA hydrolysis, soil respiration, microbial biomass carbon and bacterial community diversity, whereas positively related with fungal community diversity. The results indicate that the enhancement of soil suppressiveness against R. solanacearum by SCP application was likely due to the alteration of microbial community structure and increased competitive ability of beneficial microorganisms with pathogens. We concluded that SCP application, as a way of re-utilization of compost products have the ability to increase soil suppressive capacity against bacterial wilt.4. Temperature fluctuation and rainfall could affect the survival of R. solanacearum and the severity of bacterial wilt disease. Under lower temperature, the survival of pathogen was inhibited, whereas the control efficiency of bioorganic fertilizer and fermentation residues of CO2 fertilizer was consistent. The higher temperature could accelerate the growth and multiplication of R. solanacearum, but the control efficiency of bioorganic fertilizer and fermentation residues of CO2 fertilizer decreased. Meanwhile, we found the higher rainfall could increase bacterial wilt disease and decrease SCP control efficiency. We suggested these climate conditions above accelerate the colony of R. solanacearum and transpiration, and further induced the serious bacterial wilt.5. This present study compared the efficiencies of above three different nitrogenous amendments (calcium cyanamide, an ammonium bicarbonate and lime mixture and ammonia water) at four different nitrogen levels in suppressing the survival of R. solanacearum. The application of CC showed the best ability to suppress R. solanacearum due to its highest capacity of increasing soil NH4+, NO2-contents and pH. However, AW could be more suitable to control bacterial wilt caused by R. solanacearum, since this amendments had a lower cost and its application at rate of 0.25 g N Kg-1 could effectively suppress the survival of R. solanacearum. In addition, the three fumigants had little detrimental impacts on soil microbial activity and community structure, except to suppress R. solanacearum. Our present study provides guidance for selection of a suitable alkaline nitrogenous amendmentand its application rate in controlling bacterial wilt.6. Under high temperature (50℃), We explored the effect of three nitrogenous amendments (calcium cyanamide, an ammonium bicarbonate and lime mixture and ammonia water) above 0.25 g N kg-1 on the survival of R. solanacearum and soil microbial community structure and diversity. The survival of R. solanacearum could be suppressed rapidly by high temperature. Although microbial community populations decreased in RS and control treatment, but then they received stable levels. However, soil microbial activities and community structure showed different changes after application of the three nitrogenous amendments. At the high nitrogen level, CC, A+L and AW increased microbial activities and bacterial community populations, whereas CC and A+L decrease the fungal populations and community diversity, even suppressed the survival of fungal community. It is noted that the fungal community population was not detected in CC treatment at every nitrogen level, which has destroyed the microbial community structure. AW application still have no detrimental effect on microbial community structure. Therefore, we suggested that the combination of ammonia water and high temperature was the best and effective amendment, followed by the mixture of ammonium bicarbonate and lime incorporated with high temperature. This study provide the guide for farmer to choose the appropriate nitrogenous amendments under high temperature. |
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