ORIGINAL ABSTRACT

Synthetic herbicides are relied on for weed management in the United States, and non-chemical alternatives, such as tillage, can be inefficient and expensive at an agricultural scale. Previous research examining the influence of weed management strategies on soil microbial communities has shown variability and inconsistency in experimental design and results. This study investigates the impact of repeated applications of glyphosate, a mixture of selective herbicides, and tillage on soil bacterial communities in sugar beet production across two locations in the United States. Using next-generation sequencing and various assays, we explore the effects on bacterial community structure, composition, and function related to nutrient cycling and soil health. Although transient and minor differences in bacterial community structure could be observed for herbicides and tillage, these statistical differences do not appear to be biologically relevant as the soil function was equivalent for all applied treatments. Our findings provide evidence that repeated herbicide usage does not directly impact soil health and function in sugar beet production. This study emphasises the need for well-replicated, field-realistic, and long-term experiments to understand the ecological consequences of herbicides and tillage in agroecosystems.