Total copper content and its distribution in acid vineyards soils developed from granitic rocks

Total and extractable (5 extractants) Cu concentrations were determined in thirteen acid vineyards soils. Mean total copper concentration was 259 mg kg−1 and most of the soil samples (87%) were above the upper limit allowed by the European Union for this element in soils. The largest Cu fraction was found to be that bound to soil organic matter, which accounted for 49% of the total Cu. None of the Cu fractions showed significant differences with depth. Nevertheless, bioavailable Cu (extracted in Na2-EDTA) was found to show a strong correlation with Cu bound to soil organic matter, which may indicate that Na2-EDTA is able to extract part of the organically bound Cu, resulting in an overestimation of bioavailable Cu. However, practices associated to soil use change and management affecting the stability of Cu organic complexes could induce an increase in bioavailable Cu levels in these soils.