不同用量秸秆生物炭对辣椒疫病防控效果及土壤性状的影响

采用盆栽试验研究了不同用量秸秆生物炭对辣椒疫病防控效果及土壤性状的影响,并解析生物炭用量、土壤性状与防控效果之间的关系。结果表明,随着生物炭用量的增加,土壤pH和有机质含量逐步上升,电导率、有效磷和速效钾含量迅速上升,而铵态氮和硝态氮含量变化较小。细菌、真菌及四种功能菌数量随着用量的增加而逐步增加,但辣椒疫霉数量呈现先上升后下降的趋势。土壤酶活性方面,脲酶和β-葡糖苷酶逐步降低,FDA酶和蔗糖酶则先上升后下降。微生物代谢能力、微生物多样性及微生物均匀度均与用量呈倒U型曲线关系,在1.33%用量下获得最高值。DGGE图谱显示,低用量生物炭对微生物区系影响较小,而1.33%和2%用量则能显著改变微生物群落结构。0.33%、0.66%、1.33%和2%用量的防效分别为-9.8%、8.6%、56.7%和35.1%,与用量也呈倒U型曲线关系,1.33%生物炭用量对辣椒疫病的防效最好。一定范围内防效随生物炭用量的增加而增加,这可能是因为生物炭对土壤性状的改善作用,而随后防效下降,则与高用量生物炭对土壤性状产生的负面影响有关。

Application-Rate-Dependent Effects of StrawBiochar onControl of Phytophthora Blight of Chilli Pepper and Soil Properties

Objective]Biochar is a carbon-rich product of pyrolysis of biomass and can be used to ameliorate soil and promote crop growth. Recently,studies show that biochar has some good effects on control of soil-borne diseases. Researches in the past already demonstrated that straw biochar could effectively control Phytophthora blight of chilli pepper,through improving soil physic-chemical properties and microbiological properties,but little has been reported on how application rate affects the effect of biochar controlling the disease of Phytophthora capsici.Method]In this study,a pot experiment,designed to have 5 treatments concerning application rate,i.e. Treatment 0,1,2,3 and 4(0%,0.33%,0.66%,1.33% and 2% w/w, respectively),was carried out to investigate effect of straw biochar controlling Phytophthora blight of chilli pepper,relative to application rate of biochar. The soils in the pots were analyzed separately for chemical properties(soil pH,electrical conductivity,organic matter,ammonium N,nitrate N,available P and readily available K)and soil micro-biological properties(soil enzyme activity,microbial population, microbial community structure and soil microbial carbon utilization features). Soil microbial population was determined with the dilution plating method and real time PCR;soil microbial community structure with PCR-DGGE and soil microbial carbon utilization features with the Biolog system. Correlation analysis was done of biochar application rate,soil properties and disease control effect. Result]The disease controlling efficiency in Treatment 1,2,3 and 4 was -9.8%,8.6%,56.7% and 35.1%,respectively,forming an inverted U-shape curve. So the application rate of 1.33%(Treatment 3)was the optimal for disease control. With increasing biochar application rate,soil pH and organic matter content increased gradually,electrical conductivity,available P content and readily available K content did significantly,but ammonium and nitrate nitrogen contents did only slightly. Urease and β-glucosidase activities gradually decreased,FDA Hydrolase and sucrase activities increased first and then decreased,total bacteria,total fungi and four groups of functional microorganisms gradually increased in population,and P. capsici first increased and then decreased in population with increasing application rate of straw biochar. Microbial metabolic ability,microbial diversity and microbial community evenness all displayed an inverted U-shape curve in response to the varying application rate of straw biochar,with peaks appearing all in Treatment 3(1.33%). DGGE profiles show that biochar at low application rates(0.33% and 0.66%)had little effect on microbial community structure, but when at high application rates(1.33% and 2%)it did significantly alter microbial community structure, significantly increasing the abundance of Pseudomonas,Sphingomonas,Ascomycota and Basidiomycota.Conclusion]This study demonstrates prominently the importance of application rate of straw biochar in disease control. The control efficiency increases as application rate of straw biochar increases within a certain range,which may be attributed to the function of biochar to improve soil chemical and biological properties. But when the application rate goes beyond the range,straw biochar could weaken in control efficiency,which may be explained by the fact that too much biochar has some negative influences on soil carbon and nitrogen recycling,microbial activity and diversity. In addition,the effect of biochar controlling Phytophthora blight of chilli pepper is not much related to the population of P. capsici in the soil.