Effects Of Biochar And Trichoderma On Soil Acidification Under Continuous Cropping In Greenhouse

In the northern part of China,the area for planting vegetables is large,and the planting types are relatively single.With the increase of planting years in the facilities,the soil pH value is decreasing,and soil acidification is becoming more and more serious.Not only affect the growth and quality of vegetables,but also restrict the sustainable development of facilities vegetables.Biochar or Trichoderma can be applied to the soil alone to repair the soil environment,optimize the microbial community structure,reduce plant diseases,and promote plant growth,respectively.However,the synergistic effects of biochar and Trichoderma combined application has not been studied.In this study,the long-term continuous acidification of cucumbers in greenhouse was studied.The effects of biochar on the regulation of acidified soil and the effects of combined application of biochar and Trichoderma on the microecological environment of cucumber soil and the growth of cucumber.The main results were shown as follows:1.Different biochar additions can increase soil pH,cation exchange capacity,total exchangeable bases,and organic matter content,and reduce the total amount of soil exchangeable acids,exchangeable Al³⁺,and exchangeable H⁺.Soil pH was negatively related to the total amount of exchangeable acid,the amount of exchangeable Al³⁺,and the amount of exchangeable H⁺,and positively related to the amount of cation exchange,the content of organic carbon,and the total amount of exchangeable bases.After 180 days of cultivation,the pH of soil with pH 5.63 was applied 1%,3%and 5%biochar increased by 8.5%,11.2%and 17.2%,respectively,compared with the control.The pH of soil with pH 5.10 was applied 1%,3%and 5%biochar increased 13.5%,18.0%and 20.4%than the control,respectively.The treatment effect of 5%biochar on the two soils was the most significant,and the effect of improving the acidified soil was more obvious.2.The combined test results of biochar and Trichoderma showed that the cucumber seedlings were promoted and the root vigor was increased 3.32,2.66,4.98and 7.41 times,respectively.Meanwhile,the chlorophyll content was increased11.75%,32.68%,48.75%and 55.27%,respectively.In addition,the photosynthetic parameters and the superoxide dismutase,peroxidase and catalase activities of leaves were increased,and the content of malondialdehyde was reduced by application of Trichoderma,biochar,5%biochar combined with 0.2%Trichoderma and 5%biochar combined with 0.5%Trichoderma compared to the unapplied control.Among them,the combined application of biochar and Trichoderma on cucumber growth was more obvious than that of single application of biochar or Trichoderma.The effect of the two biochar combined with Trichoderma on the growth of cucumber seedlings was not significant.3.Biochar and Trichoderma application improved soil physical and chemical properties,increased soil available nitrogen,phosphorus,potassium and organic matter content,cation exchange capacity?CEC?and soil polyphenol oxidase,urease,catalase,sucrase activity comparing with the control without application.The single application of biochar reduced the number of soil fungi and increased the number of bacteria and actinomycetes.The number of soil fungi,bacteria and actinomycetes was increased by the combined application of Trichoderma and biochar with Trichoderma,and the soil improvement effect of latter was more significant.The difference between the two biochar and Trichoderma on the physical and chemical properties of soil was not significant.4.The combined application of biochar with 0.2%Trichoderma increased the diversity of soil bacterial communities.The combined application of biochar with Trichoderma changed the soil bacterial structure and increased the number of bacteria in Actinobacteria and Proteobacteria,the relative abundance of Firmicutes and Acidobacteria decreased.Correlation analysis of environmental factors found that soil total nitrogen,organic matter,urease activity,and soil pH had a greater impact on bacterial communities.Total nitrogen was a key factor affecting soil bacterial communities.The combined application of biochar and 0.2%trichoderma had great influence on the genetic information processing,organic system and metabolic function of soil bacteria.The combined application of biochar and Trichoderma significantly improved the function of soil bacterial metabolism and promoted soil nutrient cycling.