Summary
This comprehensive field survey of 100 organically and conventionally managed agricultural fields demonstrates that pesticide residues persist widely in soils, even under organic management, with concentrations nine times higher in conventional fields. Whilst pesticide numbers and concentrations decline significantly with the duration of organic management, residues remain detectable even after 20 years of organic farming. The study provides evidence that pesticide residues negatively affect beneficial soil microbiota, particularly arbuscular mycorrhizal fungi, suggesting they are a key environmental factor shaping soil biological communities alongside abiotic factors such as pH.
UK applicability
The findings are directly applicable to UK agricultural contexts, as pesticide persistence and organic conversion practices are comparable across northern European systems. UK organic farmers and regulators should note that conversion to organic management progressively reduces but does not eliminate legacy pesticide residues, and that soil biological recovery may be constrained by residual contamination independent of current management inputs.
Key measures
Number and concentration of pesticide residues (46 pesticides: 16 herbicides, 8 herbicide transformation products, 17 fungicides, 7 insecticides); microbial biomass; arbuscular mycorrhizal fungi abundance; duration of organic management
Outcomes reported
The study screened 100 fields under organic and conventional management for 46 pesticide residues and assessed relationships between pesticide occurrence and soil microbial communities. Key measurements included the number and concentration of pesticide residues detected and the abundance of arbuscular mycorrhizal fungi in relation to pesticide burden.
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