Effects of Some Triazole and Benzimidazole Fungicides on Metabolic Activity of Sod-Podzolic Soil

Triazole and benzimidazole fungicides, used worldwide including in Russia, persist in treated soils for a long time after application, having a prolonged effect on target and non-target soil-borne microorganisms. In this context, we evaluated the effects of difenoconazole, tebuconazole, propiconazole (triazoles), and benomyl (benzimidazole) on the metabolic activity of sod-podzolic soil from a Russian Non-Chernozem region using key soil microbiome indicators, such as basal respiration (BR), substrate-induced respiration (SIR), nitrification (NIT), and enzymatic activity. The used fungicides differed in the nature and dose-rate dynamics of their influence on these processes. Difenoconazole inhibited BR at day 7 after application when applied at a tenfold rate, while tebuconazole and difenoconazole stimulated BR at day 14. Propiconazole and benomyl taken at recommended rates increased SIR at day 7, and difenoconazole at a tenfold rate reduced SIR at days 14 and 28. Benomyl stimulated NIT at days 7, 14, and 28, while the other fungicides suppressed NIT. Triazoles decreased soil dehydrogenase activity throughout 45 days, while benomyl and difenoconazole enhanced it for 10 days. Revealing decreased and increased indicators of the soil metabolism suggests deep changes in the soil microbiome due to fungicide-induced chemical stress. Therefore, further studies of the microbiome exposed to the aforementioned fungicides by metagenomic analysis, including soil metabarcoding, are warranted.