Objectives This study aimed to clarify the effects of lime and green manure on soil physical and chemical properties, soil microbial biomass, and fungal community in continuous cropping tobacco fields, and the basis for scientific improvement of continuous cropping soil was provided.

Methods In Laifeng County, Hubei Province, a 12 year continuous cropping field with yellow brown soil was selected as the research object. Three soil improvement measures, lime (L), lime + green manure (LGM) and green manure (GM), were adopted to collect 0−20 cm soil samples from the tilled layer by 5-point sampling method. The effects of different measures on soil physicochemical properties and microbial biomass of different flora were analyzed. Illumina NovaSeq high-throughput sequencing technology and the FUNGuild platform were used to analyze the differences in soil fungal community diversity, composition structure, nutrient type composition, and functional group division in soil. The economic benefits of cigars produced by different treatments were also compared.

Results  1) The three soil improvement measures could increase the contents of total nitrogen, organic matter and available potassium to different degrees, and LGM had the best effect on enhancing soil fertility, but L had the most significant effect on improving soil acidification. L, LGM and GM treatments could significantly increase the number of bacteria and the total number of microorganisms in soil, the bacteria increased by 23.22%, 68.07% and 46.70%, and the total number of microorganisms increased by 22.06%, 62.12% and 42.42%, respectively. However, only GM treatment could significantly increase the number of fungi in soi by 12.25%. 2) The three soil improvement measures had significant effects on the soil fungal community structure, and there were significant differences among them. Specifically, the GM treatment could significantly increase the fungal community richness by 15.01% compared to the control. Treatment L could increase the relative abundance of Mucor, treatment GM could increase the relative abundance of Trichoderma, and L, LGM, and GM treatments could reduce the relative abundance of the pathogen Fusarium in soil by 19.32%, 13.78% and 9.71%, respectively. 3) LEfSe analysis results showed that the relative abundance of Chaetomiaceae in soil could be significantly improved by all three improvement measures. LGM and GM could significantly increase the relative abundance of Humicola, and L and LGM could significantly increase the relative abundance of Trichocladium. 4) FUNGuild analysis results indicated that the three improvement measures could reduce the relative abundance of pathogenic fungi and optimize the nutrient composition of fungi. 5) The average price, yield, and output value of cigars could be significantly increased by L, LGM and GM treatments, with the output value increasing by 14.56%, 27.45%, 21.47%, respectively, and the output value of LGM was significantly higher than that of L treatment.

Conclusions The three soil improvement measures could improve soil to different degrees. The GM treatment is more effective in increasing the richness of the fungal community, increasing the relative abundance of beneficial fungi, improving the nutrient composition of fungi, and optimizing the functional groups of fungi. The effects of LGM and GM treatments on improving soil fertility and the economic benefits of cigars are better than those of the L treatment.