Effects of Tilling Depth and Ridging Height on the Rhizosphere Soil Microbial Community in Tobacco Field

In order to reveal the mechanism of different cultivation methods in reducing the harmful of tobacco root-stem diseases, the effects of different tillage depths and ridge heights on the occurrence of tobacco bacterial wilt (TBW) as well as the structure of the rhizosphere soil microbial community were analyzed in this study, with a view to providing a theoretical basis for improving the soil ecological environment through cultivation measures. The results showed that compared with the control, increasing tillage depth and ridge height could significantly reduce the occurrence of TBW, and improve the alpha diversity and beta diversity indexes of soil microbial communities. The Chao1 index, OTUs number, and Shannon index of soil bacterial communities increased by 25.51%~36.03%, 25.62%~36.07%, and 10.74%~15.37%, respectively. Corresponding indices of fungal communities increased by 18.08%~ 101.12%, 18.16%~102.20%, and 48.06%~92.97%, respectively. Deep tillage and ridge height had significant impacts on the composition of soil microbial communities. At the bacterial phylum level, increasing the tillage depth and ridge height led to a significant decrease in the relative abundance of Proteobacteria and a significant increase in the relative abundances of Chloroflexi, Gemmatimonadota and Actinobacteriota. At the fungal phylum level, the relative abundance of Ascomycota significantly decreased and the relative abundances of Mortierellomycota significantly increased in the soil by increasing the tillage depth and ridge height. At the genus level, the relative abundance of bacteria and fungi significantly changed under different tilling depths and ridge heights, showing different trends. The optimal tillage depth and ridge height are both 40 cm. Under this condition, the incidence rate of TBW is the lowest. Both the alpha and beta diversity of the soil microbial communities are significantly increased, and the relative abundances of biocontrol bacteria such as Streptomyces and growth promoting bacteria such as Dongia are also significantly increased, which is beneficial for the growth and development of tobacco and reduces the occurrence of tobacco diseases.