Browsing by Person "Stache, Fabian"

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Effects of MCPA and difenoconazole on glyphosate degradation and soil microorganisms
(2024) Mäder, Philipp; Stache, Fabian; Engelbart, Lisa; Huhn, Carolin; Hochmanová, Zuzana; Hofman, Jakub; Poll, Christian; Kandeler, Ellen
Modern agriculture relies heavily on pesticide use to meet the demands of food quality and quantity. Therefore, pesticides are often applied in mixtures, leading to a diverse cocktail of chemicals and their metabolites in soils, which can affect non-target organisms such as soil microorganisms. Pesticides are tested for their single effects, but studies on their interactive effects are scarce. This study aimed to determine the effects of up to three simultaneously applied pesticides on the soil microbial community and on their special function in pesticide degradation. Agricultural soil without previous pesticide application was exposed to different mixtures of the herbicide glyphosate (GLP), the phenoxy herbicide MCPA (2-methyl-4-chlorophenoxyacetic acid) and the fungicide difenoconazole (DFC) for up to 56 days. Isotopic and molecular methods were used to investigate effects of the mixtures on the microbial community and to follow the mineralization and utilization of GLP. An initial increase in the metabolic quotient by up to 35 % in the presence of MCPA indicated a stress reaction of the microbial community. The presence of multiple pesticides reduced both gram positive bacterial fatty acid methyl esters (FAMEs) by 13 % and the abundance of microorganisms with the genetic potential for GLP degradation via the AMPA (aminomethylphosphonic acid) pathway. Both the number of pesticides and the identities of individual pesticides played major roles. Surprisingly, an increase in 13C-labelled GLP mineralization of up to 40 % was observed while carbon use efficiency (CUE) decreased. Interactions between multiple pesticides might alter the behavior of individual pesticides and be reflected in the microbial community. Our results highlight the importance of investigating not only single pesticides, but also pesticide mixtures and their interactions.
Quantification of soil microbial functional genes as potential new method in environmental risk assessment of pesticides
(2025) Stache, Fabian; Ditterich, Franziska; Hochmanová, Zuzana; Hofman, Jakub; Poll, Christian; Kandeler, Ellen
Pesticides can have adverse effects on soil microorganisms, but they are underrepresented in the currently required OECD 216 test for environmental risk assessment of plant protection products (PPP). The guideline monitors soil microbial nitrogen transformation over 28 days, potentially missing long-term effects of persistent pesticides. Additionally, nitrate alone may be not sensitive enough to detect disruptions in microbial functions. We investigated whether functional gene analysis could provide a more sensitive bioindicator of pesticide impact. To compare this method with the standard test, we conducted a microcosm experiment following the OECD 216 experimental setup. To capture long-term effects beyond the typical test period, we extended the incubation duration to 56 days. Four different concentrations of the persistent fungicide boscalid were added based on predicted environmental concentration. We also assessed microbial responses to fungicide exposure by measuring classical soil microbial parameters. According to the standard test, boscalid had no harmful long-term effects on soil microbiota. In contrast, our analysis of functional genes found an overall reduction in the acid phosphatase-encoding phoN gene abundance on Day 56, and correspondingly, in acid phosphatase activity in the highest fungicide treatment. Simultaneously, we observed a tendency towards lower fungal abundance based on measured copy numbers of an ITS region of nuclear ribosomal DNA (rDNA) and increased cumulative CO2 production. These results indicate a fungicide-related response of the microbial community and impaired microbial phosphorus cycling. Extending the experimental period to 56 days revealed long-term effects that would have otherwise been undetected under the typical 28-day test duration.