Mechanism Of Biochar And Biological Substrate To Overcome Soil Obstacles In Continuous Cropping Of Protected Vegetables

With the continuous development of facility industry in China,the area of facility cultivation is increasing rapidly.Continuous cropping is a common phenomenon in protected horticulture.Soil quality and crop yield are significantly reduced due to the increasing number of pathogens and unreasonable management of fertilizer and water.At the same time,China is a big producer of vinegar and edible fungi,producing a large amount of waste vinegar and mushroom residues every year.In the study,biochar and substrate of vinegar and mushroom residues(v:v 3:1)formed by biological fermentation as soil amendments,using pot experiment,set up five treatments without improved soil(CK),amended with commercial conditioner(C),amended with biochar(B),amended with biological substrate(VM),amended with biochar + biological substrate(VMB,1:1).The volume ratio of soil amendments to obstacle soil was 1:10.The effects of vinegar residue,mushroom residue and biochar on soil physical and chemical properties,mineral elements,soil phenolic acid and cucumber growth were analyzed.High-throughput sequencing technology and structural equation modeling were used to analyze the effects of different treatments on soil rhizosphere microbial community diversity and composition,and the relationship among soil microorganisms,environmental factors and yield to study the effect of different organic substrates on the improvement of continuous cropping obstacle soil in cucumber protected cultivation,improve the utilization of organic waste and biochar resources,and explore the effect of amendments on the maintenance of soil nutrients and the overcoming of continuous cropping obstacle.The main results are as follows:1.Biochar and biological substrate can promote cucumber growth by improving soil physical and chemical properties of continuous cropping obstacles.Biochar and biological substrate can increase value of soil p H,soil water content,organic carbon content,and significantly alleviate soil acidification.Vinegar and mushroom residue biological substrate improved the content of soil N,P,and K.In contrast,biochar substantially decreased the total phenol content and electrical conductivity.Biological substrate and biochar +biological substrate treatments significantly increased the chlorophyll content and root activity of cucumber plants.Chlorophyll a,chlorophyll b,relative chlorophyll content and root activity increased by 60.36%,90.77%,19.38% and 84.06%,respectively,when treated with biochar.Chlorophyll a,chlorophyll b,relative chlorophyll content and root activity increased by 42.01%,50.77%,19.09% and 104.18%,respectively,when treated with biological substrate.The coamendment of soil with biological substrate plus biochar is an effective method to promote cucumber growth and increase cucumber yield,and the yield was significantly increased by 49.32%.2.Biochar and biological substrate increased cucumber yield mainly by increasing soil microbial diversity under continuous cropping.The addition of single biochar and biological substrate can increase the relative abundance of copiotrophic taxa such as Actinobacteria and Gemmatimonadetes.The application of biochar and biological substrate significantly increased soil microbial diversity and culturable microbial biomass.There was a strong correlation between microbial Chao1 index and yield.Compared with soil physical and chemical properties,the correlation between soil microbial diversity and cucumber yield was stronger.3.Soil amendments formed by the mixture of biochar and biological substrate had better continuous improvement effect on the obstacles soil of protected cucumber continuous cropping.Biochar + biological substrate treatment significantly increased soil enzyme activities.Compared with CK,the activities of sucrase,urease,phosphatase,catalase,protease and polyphenol oxidase in soil were significantly increased by 81.06%,133.33%,27.73%,42.11%,12.5% and 58.92%,respectively.After continuous improvement of biochar + biological substrate treatment,total dry weight of cucumber plant,net photosynthetic rate of leaves and fruit yield increased by 41.38%,23.77% and28.56%,respectively.Principal component analysis showed that the amendments could enhance the decomposition and release of soil nutrients,promote the activity of soil enzymes and yield of cucumber.Therefore,vinegar and mushroom residue after full biological fermentation were mixed at a volume ratio of 3:1 to form a biological substrate,and the biological substrate was mixed with rice straw biochar at a volume ratio of 1:1 to form a soil amendment,which was added to the obstacles soil at a volume ratio of 10:1.It can significantly improve soil physical and chemical properties,enhance the decomposition and release of soil nutrients,enhance soil enzyme activity,improve soil microbial community structure,overcome the obstacles of continuous cropping soil,promote cucumber plant growth,increase yield,and have a continuous improvement effect on the obstacles of soil.