Occurrence of pesticide residues in agricultural soils and their impact on indicators for soil life
Pesticides are applied in large quantities to agroecosystems worldwide, leading to accumulation and dispersion of potentially persistent and toxic residues in the environment. Despite their benefits for crop yield, the intensive and widespread use of pesticides increasingly raises environmental concerns due to contamination of natural resources 1 and their negative impact on bird, insect and pollinator populations 2-4. While the occurrence and effect of pesticides in aquatic environments received considerable attention, only few reports are available on multi-residual analysis of pesticides in soils and it is still unclear whether pesticides are a potential threat to soil microorganisms, which drive pivotal soil processes such as plant nutrient uptake, carbon and nutrient cycling.
Here we provide a comprehensive overview of the presence and abundance of 45 widely applied pesticides (22 herbicides, 17 fungicides, and six insecticides) in soils of 100 agricultural fields, including 40 fields under organic management. Fields from arable and vegetable farming systems were compared and it was assessed whether the occurrence of pesticides depends on management types (conventional, conventional without soil tillage, and organic management). Moreover, we tested whether the duration of organic management affects the occurrence of pesticides. Additionally, it was assessed whether important indicators of soil life were linked to the number of pesticide residues present in the soil.
Pesticide residues were found in all of the investigated fields and up to 16 different pesticides were present in the soil 20 years after conversion to organic management. This indicates that a range of pesticides is much more persistent than previously thought. The number of pesticides in the soil was negatively linked to the abundance of an important group of beneficial soil fungi (mycorrhizal fungi). Our results indicate that the ubiquitous and continuous pollution of agricultural soils with a variety of different pesticides can have a long-term negative effect on soil life.
[1] Arias-Estévez, M., et al., Agriculture, Ecosystems & Environment, 2008, 123(4), p. 247-260.
[2] Hallmann, C. A., et al., Nature, 2014, 511(7509), p. 341-343.
[3] Sánchez-Bayo, F. and Wyckhuys, K. A. G., Biological Conservation, 2019, 232, p. 8-27.
[4] Gill, R. J., et al., Nature, 2012, 491, p.105-108.