Ecotoxicity of copper input and accumulation for soil biodiversity in vineyards

Copper has been successfully used in the sulfate form as a fungicide to control grapevine diseases since 150 years, yet high Cu accumulation in vineyards may alter soil life. Although actual Cu additions are about tenfold lower than 50 years ago, the use of Cu in the context of the agroecological transition is still debated. Indeed, copper is one of the rare pesticides allowed for organic farming. Therefore, we performed a meta-analysis on Cu ecotoxicity by selecting 19 articles out of 300 articles relevant to copper and soil biological quality. Results show that microbial activity decreased by 30% when more than 400 kg of Cu was applied yearly per ha. Nematodes abundance remained unchanged for copper application up to 3200 kg/ha/year. Collembola and enchytraeid reproduction declined by 50% after application of 400 and 1895 kg Cu/ha/year, respectively. Earthworm biomass was reduced by 15% after application of 200 kgCu/ha/year. For soil Cu levels higher than 200 kg Cu/ha, microbial respiration decreased by 50% and no effect was observed on collembola. Overall, while toxicity is observed, the corresponding literature investigations involved Cu levels that are at least 50 times higher than the dose of 4 kg Cu/ha/year currently authorized by the European Commission for viticulture. As a consequence, applying copper at 4 kg/ha/year should not modify substantially soil biological quality and functions.