| As a new microbial preparation with safety and environmental protection,lactic acid bacteria(LAB)compound preparation has become a research focus and hotspot in agricultural cultivation and soil fertilization.This experiment took saline-alkali soil in Hailiutu planting base of Hohhot City as the test object and cucumber and tomato as the test crops.The effects of microbial preparations on soil physical and chemical properties,microbial content and agronomic characters of vegetable were studied.The structure and functional genes of soil microbial communities were analyzed by using metagenomics sequencing technology,so as to provide theoretical basis for the development of new microbial preparations based on LAB and its large-scale application.The results are as follows:(1)LAB compound preparation could effectively improve the chemical properties of saline-alkali soil,but had no obvious effect on its physical properties.The proportion of solid,liquid,gas and total porosity of soil did not change significantly;the ammonium nitrogen,nitrate nitrogen and available phosphorus increased by 31.19%,46.25%and 55.05%respectively in the group A;and the pH value of soil decreased by 14.88%in the group A.(2)LAB compound preparation could effectively increase the content of four enzymes in soil,increase the number of bacteria and actinomycetes in soil,and reduce the number of fungi.The contents of catalase,phosphatase,urease and sucrase increased by 92.50%,50.13%,65.19%,49.25%in the group A respectively,and the contents of them increased by 32.50%,23.74%,23.04%and 13.68%in the group B respectively,The number of bacteria and actinomycetes increased by 57.30%and 88.30%respectively in the group A,and the number of fungi decreased by 37.50%significantly.There was no significant change in the group B.(3)LAB compound preparation could effectively promote the growth of crops,improve the yield and quality of fruits.The plant height,stem diameter,leaf area and leaf number of cucumber and tomato all increased,among which cucumber increased by 14.40%?22.0%,7.00%?13.00%,15.80%?18.00%,19.10%?22.00%,tomato increased by 14.00%?24.0%,7.00%?13.60%,18.00%?27.00%,20.50%?24.20%,respectively.Vitamin C content,soluble sugar content,fruit number per plant and yield per plant also increased significantly for cucumber and tomato,among which cucumber increased by 18.61%?35.53%,52.59%?54.40%,11.81%?15.97%,22.03%?28.81%,and tomato increased by 16.35%?31.36%,16.66%?18.54%,22.82%?25.58%,20.63%?25.39%,respectively.(4)LAB compound preparation could change the composition of soil microbial community structure and the proportion of functional genes,the relative abundance of actinomycetes increased to 8%?13%,the relative abundance of Lactobacillus reached 5%?6%,and the number of functional gene sequences involved in carbohydrate metabolism,amino acid metabolism,energy metabolism and glycoside hydrolase increased significantly.The virulence factor of soil was significantly reduced.LAB compound preparation can effectively improve saline-alkali soil,promote vegetable growth,and can regulate and optimize the structure of soil microbial communities and functional genes,which has great potential in agricultural cultivation. |
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