Short-term field effects of a flumioxazin-based herbicide on soil enzyme activities, microbial biomass, respiration, and nitrogen dynamics

Herbicides are widely recognized for their potential to affect soil microbiota, yet field data assessing the impacts of flumioxazin remain scarce. To address this gap, we evaluated short-term field effects of a flumioxazin-based herbicide (Sumisoya®; 100 g ai ha⁻¹) on key biochemical and microbial soil indicators, including enzyme activities (α- and β-glucosidase, acid phosphatase, glycine aminopeptidase, arylsulfatase), microbial biomass carbon (MBC), basal soil respiration (BSR), metabolic quotient (qCO₂), and inorganic nitrogen forms (N-NH₄⁺ and N-NO₃⁻). Application of flumioxazin significantly reduced β-glucosidase activity across the experimental period (p < 0.05) and temporarily decreased arylsulfatase activity shortly after application (p < 0.001). No significant effects were observed for α-glucosidase, acid phosphatase, and glycine aminopeptidase. Regarding nitrogen cycling, initial N-NH₄⁺ concentrations were lower in treated soils than in the control (p < 0.0001). Following herbicide application, N-NH₄⁺ increased and stabilized in the treated plots but consistently remained below control levels, with a significant difference observed at 28 days (p < 0.05). MBC increased in treated soils at 14 (p < 0.0001) and 28 days (p < 0.01), BSR increased transiently at day 7 (p < 0.05), and qCO₂ decreased significantly at days 14 and 28 (p < 0.0001), indicating altered microbial metabolic efficiency. Multivariate analysis confirmed significant interactions of treatment and time (p < 0.01). These findings highlight that flumioxazin application induces short-lived but measurable disturbances in soil biological processes.