Responses Of Rhizosphere Microbial Communities To Soil Dressing On Continuous Cropping Celery

Celery is a umbelliferae plant that is not resistant to continuous cropping,due to the limited cultivated land area,the single fertilization measures,the restrictions on planting conditions and the blind pursuit of economic interests in the cold and cool areas of Ningxia,many years of continuous cropping of celery has become a common way of planting in local agricultural production,resulting in continuous cropping obstacles.In this experiment,the field positioning experiment was adopted,and celery continuous cropping for four years was used as the research unit,and five treatments were set:conventional fertilization(CK),conventional fertilization+organic fertilizer(OF),conventional fertilization+vermicompost(VC),conventional fertilization+biological carbon(BC),conventional fertilization+fulvic acid potassium(FK),the effects of different fertilization measures on soil chemical properties,enzyme activity,microbial biomass carbon and nitrogen,agronomic traits,root antioxidant capacity,yield and quality of continuous cropping celery were studied,the changes of soil microbial community structure and flora were analyzed by Illumina MiSeq high-throughput sequencing technology,in order to screen suitable fertilization measures to alleviate continuous cropping obstacles of celery.The results of the study are as follows:1.Compared with CK,soil chemical properties and urease and sucrase activities were improved by different fertilization measures.Among them,soil pH,total salt,total nitrogen,available phosphorus,organic matter content and urease and sucrase activities were the highest in VC treatment,which increased by 1.3%,28.1%,18.5%,212.2%,82.4%,20.0%,26.1%;the contents of alkaline hydrolyzed nitrogen,nitrate nitrogen,available potassium and alkaline phosphatase activity in the soil of OF treatment were significantly higher than those of other treatments,the increase was 82.4%,117.4%,9.9%,3.2%.VC and OF treatments significantly increased soil nutrients,promoted soil enzyme activities,improve the nutrient transformation capacity of soil biological system.2.Compared with before planting,the five treatments all increased the content of organic carbon and MBN.The content of MBC increased the most in the treatment of VC and FK,which promoted the soil carbon cycle.The biomass C/N ratios of OF and VC treatments were the smallest,which respectively were 25.20 and 27.81,and the microbial entropy values of VC treatments increased,improving soil nitrogen bioavailability and organic carbon bioavailability.3.Different fertilization measures increased the number of soil fungi.Among them,VC treatment increased the soil bacterial/fungal value and the number of bacteria and total microorganisms,and the soil microbial environment gradually changed from "fungal forms "to "bacterial form";all treatments decreased soil bacterial diversity index(Shannon,Simpson index)and richness index(Chaol,Observed species index),VC and FK treatments improved fungal diversity index,and VC treatment increased the most fungal richness index.According to RDA and Pearson analysis,soil available phosphorus,MBN,total phosphorus,total nitrogen,organic matter,sucrase,urease,and catalase are the soil factors that drive the main groups of soil microorganisms,soil total salt,total nitrogen,total phosphorus,available phosphorus and organic matter are the nutrient factors that cause changes in soil microbial diversity index.Among them,the relative abundance of beneficial species of Ascomycota and Basidiomycota in soils treated with VC and FK increased significantly,and the relative abundance of pathogenic bacteria was significantly decreased,which had the best inhibitory effect on the disease incidence of continuous cropping celery.4.Compared with CK,VC and FK treatments decreased the content of MDA,increased the activity of CAT and POD in roots,improved root stress resistance,and improved the quality of celery;VC and OF treatments increased the most in celery yield and income,which were 6933 kg·666.7m-2,6067 kg·666.7m-2,the increase was 45.45%,27.3%and 68.9%,42.9%respectively.In the comprehensive evaluation of different fertilization measures,the comprehensive score of VC treatment was the highest,followed by FK treatment.Conventional fertilization combined with vermicompost and fulvic acid potassium improved soil fertility,celery yield and quality,and improved soil microbial community structure.Therefore,it is recommended to use conventional fertilization combined with vermicompost or conventional fertilization combined with fulvic acid potassium treatment as a fertilization system for the scientific and rational planting of Xiji celery.