Assessment of the impact of isoproturon, tebuconazole and chlorpyrifos on soil microbial abundace and functions using a lab-to-field tiered approach

EABIOMEUBINRA DOCTPesticides are applied to protect crops against pests and diseases. Following their application, they can persist in soil and induce toxic effects on non-target soil organisms including soil microorganisms which have a pivotal role in soil ecosystem functioning. However, the pesticides registration in EU evaluates their impact on the soil microbial community through the application of two simple C and N mineralization tests which do not provide a comprehensive view of their soil microbial ecotoxicity of pesticides. In the IAPP Marie Curie project “LOVE TO HATE”, we propose the development of a tiered lab-to-field approach to assess the soil microbial toxicity of pesticides. Following this tiered approach, we studied the impact of three pesticides (isoproturon, tebuconazole, chlorpyrifos) commonly used at EU level. In the laboratory study (Tier I) the application of tebuconazole and chlorpyrifos have induced a significant effect on the abundance of the 11 microbial groups analysed and the structure of bacterial community although these effects did not show a clear time-dependent pattern. In contrast, the ammonia-oxidizing microorganisms (AOA and AOB) were most responsive to tebuconazole and chlorpyrifos. No significant effects on denitrification genes were seen. In the field study (Tier II), AOA and AOB abundance was reduced in response to all three pesticides tested. No significant effects on the denitrification genes was observed in Tier II. In conclusion, the application of the three pesticides did not appear to induce clear toxic effect on the soil microbial community. The only exception was the significant reductions in the abundance of microbial nitrifiers which appeared to be the most sensitive at this type of abiotic stress