Deep tillage inhibits microbial species interactions and exhibits contrasting roles in bacterial and fungal assembly

Abstract

Tillage is an important agricultural practice influencing soil ecosystem functions, but much uncertainty remains concerning adaptations of soil microbial communities to tillage practices and the subsequent impacts on soil quality and crop yields. We investigated the microbial community compositions and ecological characteristics in both top and subsoils undergoing different tillage regimes with crop residue retention: no tillage, rotary tillage and deep tillage. The crop yield increased by 24–47% in deep tillage combinations compared with rotary tillage and no tillage. Deep tillage combinations increased the diversity of both bacterial and fungal communities and led to more unique species with yield-increasing potential than no tillage. Both deep and rotary tillage had negative impacts on species interactions than no tillage, with a stronger effect in deep tillage combinations. Compared with no tillage, the contribution of stochastic processes increased by 4–9% in the bacterial assembly but decreased by 4–14% in the fungal assembly in deep tillage combinations. Furthermore, the fungal community composition in the top soils, which was affected by the alkali-hydrolysable nitrogen content, was the strongest driving factor of yields. The deep tillage combinations enriched symbiotrophic fungi, which had positive correlations with the yields. In conclusion, compared with no tillage, deep tillage combinations harbored microbial communities with distinct characteristics, including higher diversity, weaker species interactions, more stochastic processes in bacterial assembly and more deterministic processes in fungal assembly. The crop yields were driven by fungal community composition in top soils, with the higher abundance of symbiotrophic fungi resulting in higher yields.