Concerted Evaluation of Pesticides in Soils of Extensive Grassland Sites and Organic and Conventional Vegetable Fields Facilitates the Identification of Major Input Processes

Summary in the original language of the document

The intensive use of pesticides and the subsequent diffusion of these active molecules in the environment and in non-target organisms are increasingly worrying. Few studies have analyzed the presence of pesticides in soils of untreated areas that serve as ecological refuges (e.g. meadows). A lack of knowledge is also observed at the level of the processes of (unintentional) contamination of these untreated surfaces. This study, conducted in Switzerland, analyzed the presence and abundance of 46 pesticides in soils of extensively managed meadows, as well as in vegetable fields managed in organic and conventional agriculture (60 plots in total). Pesticides were found in all soils, including in extensive meadows, demonstrating a background and generalized contamination of soils by pesticides. The results obtained also suggest that fields initially managed in conventional agriculture, then converted to organic agriculture, reach pesticide levels as low as those of meadows only twenty years later, which illustrates the persistence of pesticides in soils. The analysis of the different pesticide compounds found in meadows and organic fields made it possible to differentiate the presence of pesticide residues due to long-term persistent molecules from presences due to diffuse contamination processes (spray drift during conventional field treatments and atmospheric deposition).