Impacts of tillage system on soil fungal communities

Soil microbiomes play fundamental roles in ecosystem functioning, including through influences on plant health, soil structure, and nutrient transformations. Agricultural practices such as tillage can significantly impact soil microbiomes through direct impacts on microbes and by altering soil physical and chemical properties. A field experiment conducted in Portage la Prairie, Canada, assessed the effects of four different tillage systems (in order of increasing soil disturbance: vertical tillage, conventional tillage, deep tillage, and raised bed formation) on soil fungal communities within different soil fractions (particulate organic matter, aggregates < 2 mm, aggregates > 2 mm). Soil samples were collected in 2021 and 2022 across three fields representing different crop rotation phases. Profiling fungal communities via amplicon sequencing revealed substantial diversity, with Alternaria and Fusarium among the most frequently detected phytopathogenic genera. Fungal community composition was distinct and fungal community diversity was higher in soil aggregates compared to particulate organic matter. Tillage significantly influenced fungal diversity, with less disruptive tillage systems supporting higher fungal diversity within soil aggregates, compared to more disruptive tillage systems. Relative abundances of arbuscular mycorrhizal fungi varied with soil fraction and prior crop identity. In 2021, Glomeromycota abundance was higher in large aggregates, reduced under more intense tillage regimes, and lower following canola. The relative abundances of several fungal taxa helped to explain observed pathogen inhibitory activity. This study highlights the dynamic nature of fungal communities, their responses to tillage, and their variation among soil fractions. Understanding how agricultural management affects linkages between soil structure and the microbiome is crucial for anticipating impacts of agricultural management regimes on soil biology. • Fungal communities differ broadly between particulate organic matter vs. within soil aggregates. • AMF showed higher relative abundance in large soil aggregates. • AMF showed lower relative abundance under the most disruptive tillage practices and following canola. • In one year, less disruptive tillage practices supported higher fungal diversity in large soil aggregates. • Abundances of Nectriaceae, Fusarium oxysporum , and Murispora sp. were positively related to inhibition of F. graminearum .