Copper (Cu) and zinc (Zn)
Copper is also one of the most widely studied elements in wine-growing regions because the treatment and prevention of vine downy mildew is commonly carried out using the Bordeaux mixture (Ca(OH)2+ CuSO4). However, copper becomes toxic to plants and some micro-organisms when it is present at high levels in soils as it disrupts nutrient-cycling and inhibits the mineralisation of essential nutrients.
In the soils under discussion here, copper was present in an acceptable medium level (Table 3), i.e., between 25.0 mg·kg–1(topsoil) and 23.7 mg·kg–1 (subsoil). The world average level in soil is 30 mg·kg–1 (from 2 to 250 mg·kg–1, Adriano 2001) and the normal variation in soils is between 5 mg·kg–1 and 50 mg·kg–1 (Bloemen et al. 1995). A mean value of 35.4 mg·kg–1 has been determined in Spain (Peris et al. 2007), 24 mg·kg–1 (from 1 to 111 mg·kg–1) in Portugal (Reis et al. 2007), 227 mg·kg–1 in France for the deep horizon (Chopin et al. 2008), while in Brazil the content is in the range from 50.1 mg·kg–1 (20 years) to 2197 mg·kg–1(100 years) (Mîrlean et al. 2007). The pedogeochemical baseline level for Castilla-La Mancha is 10.3 mg·kg–1 (Jiménez- Ballesta et al. 2010).
The average contents in Zn (Table 3) are 47.4 mg·kg–1(topsoil) and 43.6 mg·kg–1 (subsoil). According to other authors the values for Zn range between 10 mg·kg–1 and 300 mg·kg–1 (Adriano 2001), with a world soil average of 50 mg·kg–1, so contamination is not evident for this element. In Castellon (Spain) the average value is 76.8 mg·kg–1 (Peris et al. 2007); in the Champagne region of France (Chopin et al. 2008) the values range from 318 mg·kg–1 in the topsoil to 208 mg·kg–1 in the deep horizon, with 75 mg·kg–1 as median; and in Portugal (Reis et al. 2007) a minimum value of 14 mg·kg–1 and a maximum value of 344 mg·kg–1 were determined for vineyard areas. Finally, the pedogeochemical baseline level for Castilla-La Mancha (Central Spain) is 35.7 mg·kg–1 (Jiménez Ballesta et al. 2010). Increased concentrations of Zn and Cu in soils under the long-term production of grapevine have been recorded in numerous studies (Romić and Romić 2003; Fishel 2014; Tóth et al. 2016).