Comprehensive Study of Difenoconazole in Soil: Kinetics, Dissipation, Metabolism, and Microbial Toxicity

Difenoconazole is a persistent and widely used fungicide, but comprehensive long-term studies on its dissipation/degradation in soil and its influence on the soil microbiota are still lacking. Here, on the one hand, a long-term study of its dissipation/degradation in soil, after the application of a commercial product, has been carried out under laboratory conditions (2 doses and 2 soils) and field conditions (greenhouse, 1 dose and 1 soil). The results have revealed that the difeconazole had half-life (DT50) values over 175 days under laboratory conditions and over 115 days in the field trial. In general, difenoconazole tends to be more persistent in clay soils and when applied at higher doses. A total of eight metabolites were tentatively identified during the degradation process; one of them had not been previously described in soils. The main metabolite was difenoconazole alcohol, which exhibited high persistence (detected for more than 100 days in soils), indicating the risk of exposure not only to the active substance. On the other hand, the effect of difenoconazole on soil microbiota was tested in the laboratory after 3 months of exposure at the recommended dose in two soils. Under these conditions, the microbial activity and functionality were not affected by the application of the fungicide. However, a slight increase in microbial activity was observed following the application of difenoconazole. This increase was not associated with a negative impact on microbial functionality but rather suggests a potential adaptive response to the fungicide. These results highlight the influence and interaction of biotic and abiotic factors in the soil with respect to disturbances in the ecosystem.