Effects Of Returning Sorghum To Field On Soil Chemical Properties And Microbial Community Of Continuous Cropping Vegetables

Facing some obstacles such as deterioration of soil chemical quality,imbalance of microbial community and decline of yield and quality of protected vegetables.This paper aims to explore the effects of sorghum straw returning irrigation and plastic film mulching and adding sorghum stubble rhizosphere soil on the soil chemical properties,microbial community and biological characteristics of continuous cropping vegetables by pot(box)experiment based on the selection of sorghum varieties that can secrete biological nitrification inhibitors by hydroponic experiments and the determination of planting density by field experiments,clarify the effect of returning sorghum to the field on alleviating soil continuous cropping obstacles,and provide technical support for ecological prevention and control of continuous cropping obstacles and healthy development of facility industry.The main results are as follows:(1)The concentration of methyl p-hydroxyphenylpropionate secreted by sorghum roots in hydroponic culture experiment ranged from 2.12?5.89 ?g·L-1,and "Jiniang No.3"had the highest secretion.The relationship between planting density and biomass of sorghum accords with the quadratic function y=-0.0027x2+0.2022x-0.2281(F=8.571,P=0.043),and the biomass of sorghum is the largest when the planting density is 3.74×105 plants·hm-2.(2)The soil available potassium and nitrate nitrogen content of sorghum straw returning irrigation and plastic film mulching continuous cropping tomato increased significantly by 72.34%and 43.60%,respectively,which increased the soil pH to a certain extent.The content of total phosphorus,available phosphorus and available potassium in continuous cropping cucumber soil with sorghum stubble rhizosphere soil increased significantly by 8.28%,16.26%and 89.22%,respectively,while the content of ammonium nitrogen decreased significantly by 36.12%,and the soil pH decreased significantly.(3)Returning sorghum straw to the field with irrigation and film mulching significantly increased the OTU_richness and Shannon index of bacteria;And significantly improved the abundance of Proteobacteria,Firmicutes and Bacteroidetes,but decreased the abundance of Acidobacteria,The abundance of Acremonium,Penicillium and Aphanoascus decreased in fungi.Principal coordinate analysis shows that the difference in bacterial and fungal community composition mainly comes from between groups.The addition of sorghum root stubble rhizosphere soil significantly increased the OTU_richness,Shannon and Simpson indexes of bacterial;And increase the abundance of Acidobacteria and Bacteroidetes,but decreased the abundance of Proteobacteria,Firmicutes and Nitrospirae,and decreased the abundance of Bacillus at the genus level;In fungi,the abundance of Trichoderma and Pseudeurotium increased while the abundance of Fusarium and Metarhizium decreased.Further quantitative detection of Fusarium found that the gene copies Fusarium in the rhizosphere of sorghum stubble decreased significantly by 81.08%.Under the treatment of sorghum straw returning to the field,irrigation and mulching,the community variation of bacteria and fungi was most correlated with available potassium(P=0.034,F=5.8)and pH(P=0.044,F=5.1),respectively;Under the treatment of adding sorghum root stubble rhizosphere soil,the community variation of bacteria and fungi was most correlated with nitrate nitrogen(P=0.048,F=3.5)and organic matter(P=0.018,F=3.4),respectively.In addition,the number of 16S rRNA and ITS rRNA genes in the rhizosphere soil of sorghum stubble significantly increased by 97.5%and 74.2%,respectively.(4)The yield and biomass of tomato increased by 113.26%and 165.63%respectively.Adding rhizosphere soil of sorghum stubble improved the growth and development of cucumber and increased the survival rate of plants.In conclusion,returning sorghum straw to the field for irrigation and film mulching and adding sorghum stubble rhizosphere soil play a positive role in promoting vegetable growth,which improves soil chemical properties and microbial community structure,and provides a feasible solution to alleviate the obstacles of continuous cropping of vegetables.