Soil depth determines the microbial communities in Sorghum bicolor fields

Abstract

Sorghum bicolor, an important global crop, adapted to thrive in hotter and drier conditions than maize or rice, has deep roots that interact with a unique and stratified soil microbiome that plays a crucial role in plant health, growth, and carbon storage. Microbiome studies on agricultural soils, particularly fields growing S. bicolor, have been mostly limited to surface soils (<30 cm). Here we investigated the abiotic factors of soil properties, field location, depth, and the biotic factors of sorghum type across 38 genotypes on the soil microbiome. Utilizing 16S rRNA gene amplicon sequencing, our analysis reveals significant changes in microbial composition and decreasing diversity at increasing soil depths within S. bicolor regardless of genotype or fields. Notably, specific microbial families, such as Thermogemmatisporaceae and an unclassified family within the ABS-6 order, were enriched in deeper soil layers beyond 30 cm. Additionally, microbial richness and diversity declined with depth, reaching a minimum at the 60 - 90 cm layer, with layers beyond 90 cm increasing in alpha diversity. These findings highlight the importance of soil depth in agricultural soil microbiome studies.