Abstract: Excessive use of chemical fertilisers will change the physical properties of the soil and destroy its structure, and coupled with the effects of continuous cropping barriers, soil nutrient effectiveness will be severely reduced. In this paper, the effects of microbial agents on the physicochemical properties and microbial community structure of soil planted with Ophiopogon japonicus and its soil, which is widely planted in Santai County, Mianyang City, Sichuan Province, the largest Ophiopogon japonicus planting base in the country, were investigated by using the third-generation high-throughput sequencing Illumina MiSeq. The results of the study showed that the yield of Ophiopogon japonicus increased from 5 344.05±987.00 kg/hm² to 6 501.45±1 154.10 kg/hm² by 21.63% (P<0.05) after the application of microbial agents. Soil pH significantly increased from 6.50±0.24 to 6.86±0.11 (P<0.05). At the same time, soil organic matter, total nitrogen and total phosphorus content increased to varying degrees. Correlation analysis showed that soil pH and total nitrogen profoundly affected the yield of Ophiopogon japonicus with significant (P<0.05) and highly significant (P<0.01) correlations, respectively. The use of fungicides changed the soil microbiological environment, and the relative abundance of bacterial Acidobacteria, Chloroflexi, and Firmicutes in the soil was significant increased after fungicide application (P<0.05), and that of fungal Basidiomycota was significantly increased (P<0.05); among them, the relative abundance of Bacillus and unclassified_Chaetomiaceae, which had good resistance to plant pathogens, also increased significantly (P<0.05). Correlation analysis showed that the yield of Ophiopogon japonicus was significant positive correlated (P<0.05) with the relative abundance of Bacillus, Nitrosomonadaceae_MND1, Rokubacteriales, Nitrospira, and unclassified_Chaetomiaceae significantly positive correlated (P<0.05) and significantly negative correlated (P<0.05) with the relative abundance of Pseudogulbenkiania. This study showed that the application of microbial fungicides increased the pH of the soil planted with Ophiopogon japonicus, alleviated acidification, and increased the total organic matter, total nitrogen and total phosphorus contents of the soil. Meanwhile, the application of microbial fungicides improved the structure of soil microbial community. The results provide a theoretical basis for the application of microbial agents in the ecological cultivation of Ophiopogon japonicus.

Key words: microbial agents, Ophiopogon japonicus, yield, soil microorganisms, micro-ecology