Research On Soil Obstacle Diagnosis And Reduction Techniques In The Main Production Areas Of Protected Melon And Vegetable In Jiangsu Province

In order to meet the increasing demand of agricultural market,protected cultivation has become an important way of fruit and vegetable production worldwide in the last decades.At present,the protected vegetable production accounts for almost one third of all vegetables in China.Protected cultivation has changed the natural farmland ecosystem.Because of its special planting conditions,it tends to cause soil secondary salinization,soil hardening,accumulation of soil nutrients,salt and H+in the surface layer,unbalanced nutrient supply,diseases,etc.This will interfere with crop growth,causing the decline of crop yield and quality,which seriously restricts the sustainable development of protected agriculture.Therefore,it is particularly important to investigate the obstacles of protected soils,clarify the causes of soil obstacles and find effective solutions for restoring and maintaining the health and vitality of agricultural soil,protecting farmland ecosystem and realizing the sustainable development of protected agriculture.Jiangsu province is one of the most important production areas of protected agriculture in China,with serious problems of soil obstacles.This thesis collected soils from the representative planting areas of northern,central and southern Jiangsu,followed by the determination of soils physiochemical and microbial properties.A pot experiment was set up to explore the effects of balanced fertilization on tackling soil obstacles.Based on the nutrient contents in the soil with obstacles,a series combination of medium and trace elements were added.The variation of Chinese cabbage biomass,soil physiochemical properties and soil microbial community composition under different treatments were observed.The results are as follows:1.Generally,the pH decreased,while soil electric conductivity increased,after continuous mono cultivation in the vegetable and melon producing areas in Jiangsu Province.Water-soluble sodium and calcium account for a large proportion in those deteriorate soils,with the NO3--N and available P content higher than 300 mg/kg.The supply level of soil trace elements generally declined.2.Except Pukou base,the Sobs index,ACE index and Chao index of microbes were higher than protected soils without continuous cropping.The dominant bacteria phyla included Proetobacteria(20.98%on average),Actinobacteriota(17.22%),Chlorobacter(14.59%),Acidobacteriota(14.32%),Fimicutes,11.85%),Gemmatimonadota(4.22%)and Bacteroidota(3.19%),accounting for 86.38%of the total bacteria.Except Pei County base,the relative abundance of Proteobacteria and Actinomycetes was higher in protected soils without continuous cropping.The dominant bacteria genus was Bacillus,accounting for 5.1%averagely.Except for Pukou base,the relative abundance of Bacillus was higher in the protected soil with continuous cultivation.3.The dominant fungi includeed Ascomycota(71.59%),Mortierellomycota(12.5%),Basidiomycota(9.3%)and unclassified k Fungi(5.1%).The relative abundance of Ascomycetes was higher in protected soils without continuous cropping at Pukou,Haimen,Sucheng and Peixian,but lower at Dantu and Ganyu base.4.The soil pH in protected soil with obstacles was lower,while the contents of organic matter,available N,P,K and available Zn are higher,than that in open-air farmland in the same area.The contents of available Fe,Mn and Cu are complex,without a clear pattern.The content of available Mo in greenhouse soil was lower than open-air farmland,but there was little difference in available B content.All nutrients were the highest in 0-20cm soil surface layer,and there were still remarkably concentrations accumulated at 80-100cm,with a potential risk of leaching and water pollution.5.Soil nutrient status was adjusted based on the result of soil determination.The best growth of Chinese cabbage was obtained in the treatment with relatively lower level of calcium and magnesium fertilizer.With the increase of fertilization amount,soil available iron(Fe),manganese(Mn),copper(Cu)and zinc(Zn)trended to decrease,while other other nutrients did not change dramatically.The number of culturable bacteria increased first and then decreased,while the number of cultrable fungi increased,with the increase of fertilizer rate.The optimal fertilization increased the richness of soil microorganisms.The relative abundance of Proteobacteria,Firmicutes,Gemmatimonadota and Bacteroidota increased,while the relative abundance of Actinobacteriota,Chlorotlexi and Patescibacteria decreased.As far as Fungi was concerned,the growth of Chytridiomycota and Mortierellomycota,especially Fusarium,were inhibited by balanced fertilization.More,balanced fertilization was beneficial for bactderial metabolic processes.Among all environmental factors,pH and available molybdenum(M o)in soil affected the changes of dominant bacterial groups the most.