Effects of high carbon base fertilizer on fungal community structure in flue-cured tobacco soil and tobacco leaf quality under nitrogen reducing condition

【Objective】 Exploring the effects of applying high carbon base fertilizers under nitrogen reduction conditions on the fungal community structure in the rhizosphere soil of flue-cured tobaccoand tobacco leaf quality, providing theoretical reference for soil conservation, microbial community regulation, and improving tobacco leaf quality in tobacco rice rotation in southern tobacco regions.【Method】 Using a field trial design, two treatments were set up, conventional fertilization control(CK) and application of high carbon base fertilizer under nitrogen reduction conditions(T):15% reduction in nitrogen compared to conventional fertilization+600 kg/ha of high carbon base fertilizer. The Illumina highthroughput sequencing technology was used to analyze the structure of soil fungal communities. NMDS analysis and Pearson correlation analysis were used to analyze the differences in soil fungal community structure and the correlation between soil nutrients and fungal abundance. The chemical composition and neutral aroma substance content of tobacco leaves were also measured.【Result】 Under nitrogen reduction conditions, the application of high carbon base fertilizer can significantly improve soil quality(P<0.05, the same below). Compared with CK, the soil moisture content, pH, organic matter, alkaline nitrogen, microbial biomass carbon, and microbial biomass nitrogen content of T treatment increased by 24.17%, 20.42%, 23.59%, 17.41%, 108.32%, and 92.24% respectively. Under nitrogen reduction conditions, the application of high carbon base fertilizers changed the diversity and richness of soil fungi, and the Simpson index of soil fungal communities significantly increased. observed OTU number, Chao1 index, and Shannon index decreased. It could also improve the structure of rhizosphere fungal communities, especially the relative abundance of functional microorganisms, such as Basidiomycota and Ascomycota, which have increased relative abundance by 20.35% and 4.63% respectively. The correlation analysis results indicated that there was significant correlation between the phyla Basidiomycota, Olpidiomycota, and Blastochadiomycota in soil and soil physicochemical properties and microbial biomass carbon and nitrogen. In terms of tobacco quality, the total sugar content, reducing sugar content, sugar-alkali ratio, total sugar-reducing sugar ratio, and total neutral aroma substances of cured tobacco treated with T increased by 18.26%, 28.10%, 30.98%, 7.31%, and 13.11% respectively.【Conclusion】 Applying high carbon base fertilizer under nitrogen reduction conditions can improve the physical and chemical properties of tobacco rice rotation soil in southern tobacco growing areas, regulate soil fungal community structure, coordinate tobacco chemical composition, and increase tobacco yield and quality.