The accumulation of copper in a New Zealand orchard soil

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Abstract
Overseas research has demonstrated that high concentrations of copper can build up in orchard soils as a result of the use of copper-based fungicide sprays. However, there appear to be no published estimates of copper accumulation in New Zealand orchard soils. In this study, soil and grass samples were taken from an orchard in North Otago, and from a nearby pasture site, to assess the accumulation of copper derived from fungicide sprays. The mean total copper content of the orchard soil was 100 µg/g (±SD 46.80 µ/g), compared with the pasture site with 32.38 (µ/g (± 0.94 (µ/g). The grass samples from the orchard had a mean total copper concentration of 19.98 µ/g (± 17.18 µ/g), while the corresponding figure for the pasture grass samples was 6.71 µ/g (+ 2.19 µ/g). We conclude that, after only 16 years of spraying, the use of copper-based fungicides has resulted in significantly higher concentrations of copper in the orchard soil, compared with the nearby pasture soil. The mean concentration is approaching levels at which some plants can show signs of toxic effects, and the implications of the use of old orchard soils, which might contain substantial concentrations of accumulated copper, for other purposes are discussed.