Copper content and distribution in vineyard soils from Betanzos (A Coruña, Spain)

The sustained use of cupric compounds in grape production has contributed to a pronounced Cu accumulation in vineyard soils. We studied 32 surface (0-20 cm) vineyard soil samples from the Atlantic-influenced NW Iberian Peninsula, in order to assess the Cu levels in these soils. The total Cu (CuT) contents were high and variable (between 63-730 mg kg-1), similar to those previously found in the Ribeira Sacra and O Ribeiro denominations of origin, which were until now the areas with the highest CuT concentrations detected in vineyard soils of the NW Iberian Peninsula. Most Cu in the solid phase of the soil was bound to organic matter (18-373 mg kg-1), contrary to what happens in natural soils or with elements from natural sources, such as Zn, for which the residual fraction is quantitatively the most important. The exchangeable Cu fraction was the fraction that showed the highest geochemical mobility and its variance in the studied soils was mainly related to CuT and, secondly, to exchangeable Ca levels. The results of fractionation were clearly different from those of Zn, an element with a mainly natural origin, which was characterized by a dominant residual fraction. Finally, agricultural practices aimed at maintaining or increasing the amount of organic matter in vineyard soils should be encouraged, due to its role in decreasing the eventual toxic effects of high Cu levels both on plants and on soil microorganisms.