Copper content in agricultural soils related to cropping systems in different regions of Greece

Copper (Cu) is naturally present in all soils with a normal range of 2-60 mg kg(-1). The traditional use of Cu fungicides against mildew diseases has led to the accumulation of Cu in some vineyard and orchard soils. Consequently, there is a move to reduce the use of these compounds in agriculture, especially in organic cultivation. A comprehensive study has not been made of the Cu content of Greek agricultural soils, which are typically alkaline with high clay content and may, therefore, be vulnerable to Cu accumulation. Within the framework of various projects, surface soil samples were taken from 10 different regions of Greece for various representative crops, and especially, for fallow soil and abandoned land. The samples were analyzed for total (aqua regia digestion) and DTPA-extractable Cu content and for several physical and chemical properties. Mean values of total Cu for the different regions of the country ranged from 16 (Limnos and Thera) to 89 mg kg(-1) (Nemea), with an overall mean of 38 +/- 26 mg kg(-1). Significantly lower Cu content (27 mg kg(-1)) was found for annual than for other crops. The mean values for fallow land, vines, and olives were close to the overall mean, but for citrus the mean value was slightly higher. The highest value of 70 mg kg(-1) was found for orchards/nuts (n = 14) which also had the highest mean value for DTPA-extractable Cu (20.2 mg kg(-1), n = 10) and is indicative of some Cu accumulation in these soils. Although the mean Cu content for vineyard soils was relatively low, higher values were noted for the old vineyards of Nemea, where the extensive use of Cu fungicides is necessary to control mildew diseases. However, values > 100 mg kg(-1) were found for only 18 of 540 soils, mostly from orchards and vineyards. No differences were found between the Cu content of organically and conventionally cultivated soils. Overall, Greek soils do not appear to have been vulnerable to Cu accumulation as the result of the traditional application of Cu fungicides, indicating that their continued use in organic farming may be compatible with the philosophy of environmentally friendly fanning under the growing conditions prevalent in the country.