Pesticide mixtures affect soil fauna and vegetation of arable fields and bordering grasslands

Pesticides can harm non-target soil fauna and plant communities. Their influence may extend to sites adjacent to agricultural fields, including protected areas. We measured contamination (type, number and concentration) of currently used pesticides and the physicochemical parameters in soils of agricultural fields and adjacent dry grasslands in two regions of Germany. We assessed their effects on community structure and species diversity of vegetation, soil nematodes and oribatid mites to see whether they were comparable between groups. The fields had higher pesticide numbers and concentrations compared to the grasslands, and lower species richness for all three taxonomic groups. We found a significant negative correlation between the total number of pesticides in a soil sample and the species richness of plants and nematodes. In addition, herbicide mixtures reduced species richness of plants and root-feeding nematodes, and fungicide mixtures reduced species richness of plants and nematodes. There was no clear effect of pesticides on oribatid mites. The inconsistent response of different taxa to pesticides calls for usage of natural communities in impact assessments. Pesticide effects in protected sites near agricultural fields suggest establishment of buffer zones. • We studied responses of soil fauna and vegetation to pesticide contamination. • Pesticide mixtures reduce nematode and plant richness in arable fields and bordering grasslands. • Herbicides reduce nematode root feeder and plant richness, fungicides plant and nematode richness. • Effects partially override abiotic parameters in arable fields. • Results suggest use of buffer zones and natural communities in pesticide risk assessments.