Copper Leaching in Vineyard Soils Following Bordeaux Mixture Application: Column Experiments

Considering that copper-based fungicides, particularly Bordeaux mixture, accumulate in vineyard soils and may pose risks of Cu leaching to groundwater, this study quantified Cu leaching from ten vineyard soils, assessing the influence of soil pH and organic matter (OM) and the effect of short-term aging on Cu mobility. Column leaching experiments were conducted with ten vineyard soils differing in pH and OM, spiked with 0-800 mg Cu kg− 1 as Bordeaux mixture. Leachates were collected over 14 h, and cumulative Cu release curves were fitted to kinetic models. Freshly spiked soils were compared with soils incubated for 30 days to assess short-term aging effects. Cu leaching from historically contaminated soils was extremely low ( 200 mg L− 1 in acidic soil), whereas realistic applications (50 mg Cu kg− 1) released < 5% of added Cu. Short-term aging had no significant effect. Typical Bordeaux mixture applications pose limited Cu leaching risk, although acidic and OM-poor soils are more vulnerable. Importantly, these results indicate that studies of Cu mobility using pure Cu salts, which are rarely used as fungicides under field conditions, may overestimate Cu mobility and leaching potential compared to Bordeaux mixture, which represents a form of Cu widely applied in realistic viticultural settings.