Rescue of herbicide-suppressed soil bacterial communities by metallic micronutrients links to improved soil aggregate...

Metallic micronutrients have the potential to alleviate herbicide-induced impairment of soil bacterial communities and then improve aggregate stability. A survey of maize-producing regions across China was executed to reveal the relationships among typical herbicides, metallic micronutrients, bacterial communities, and soil aggregate stability. Subsequent field trials were conducted to assess the impacts of atrazine, acetochlor, thiencarbazone-methyl·isoxaflutole (TMI), and metallic micronutrients on functional genes. The survey showed that atrazine and acetochlor were negatively correlated with the abundance of the denitrification gene nirS and the proportion of macroaggregates. Structural equation modeling (SEM) demonstrated that atrazine and acetochlor suppressed the proportion of macroaggregates, mainly via reduced nirS abundance, lower soil pH, and decreased microbial diversity. Geodetector analysis further identified joint effects between atrazine and acetochlor, suggesting stronger combined associations with reduced nirS abundance and macroaggregate proportions. SEM analysis indicated that zinc mitigated the impairment of atrazine and acetochlor on the soil aggregates stability by enhancing nirS abundance. Iron exhibited a positive direct path coefficient to macroaggregate proportions. Controlled field trials further verified that atrazine, acetochlor, and TMI significantly reduced nirS abundance relative to the herbicide-free control, whereas zinc amendment significantly increased nirS abundance under TMI exposure, as supported by variance analysis. Consequently, metallic micronutrients can alleviate the inhibitory impacts of herbicides on the abundance of genes involved in essential bacterial functions, and exhibit potential in maintaining soil aggregate stability.