Figure 2
The elementary compositions of the soils of Alcubillas allowed us to establish the pedogeochemical baseline levels and these are relevant because they allow the distinction of contaminated areas from uncontaminated ones. The absence of potentially polluting industrial activities in the area of study means that most of the potentially polluting chemical elements are at concentrations close to the pedogeochemical baseline levels of the region (Jimenez Ballesta et al. 2010), i.e., they are directly associated with the existing lithological units or weathering processes.
It should be noted that the foliar application of fungicides or the addition (direct or irrigated) of phosphate fertilizers (with impurities that contain heavy metals such as Cd, Hg and Pb, Ramalho et al. 1999; Nagajyoti et al. 2010) contribute to increased contents in soils, so it was expected that the vineyard soils of Alcubillas would have higher than normal contents in some PTEs. It is worth noting that Cu values have been reported for the soils of traditional wine regions throughout the world. For example, these values range from 20 to 500 mg·kg–1 Cu in France (Flores-Véles et al. 1996; Brun et al. 1998), 35 to 600 mg·kg–1 in Spain (Arias et al. 2004), 2 to 375 mg·kg–1 in Italy (Toselli et al. 2009), 100 to 210 mg·kg–1 in Greece (Vavolidou et al. 2005) and 40 to 250 mg·kg–1 in Australia (Pietrzak and Mcphail 2004). This is not the case for Alcubillas, where the common feature is the addition of organic residues that are mainly of plant origin (pruning residues) to which goat and sheep excrement is added.
In Alcubillas farmers are aware of this situation and they fertilize soils with only moderate doses with a low frequency of application. The farmers also control the changes that occur during the development and growth of the crop. In fact, even if the farmers are not aware of the origins, they observe structural, biochemical and physiological changes through visible symptoms of phytotoxicity such as reduced growth (especially of the root system), chlorosis and necrosis in the leaves.
On the basis of the Cu values found, one can expect shortening and thickening of the apex of the vine root (Ambrosini et al. 2015) along with an increase in the number of lateral roots and plasmolyis in the epidermis of some cells, thus reducing the density of the root hairs (Chen et al. 2013; Zhang et al. 2014). In addition, the presence of excess Cu in plant shoots can lead to a decrease in the concentration of photosynthetic pigments and the fixation rate of C. These changes may in turn increase oxidative stress at the cellular level (Cambrollé et al. 2013). However, these symptoms were not observed in the studied area, because Cu-fungicide applications are minimal to achieve desired effects. The farmer is aware of this and avoids incorporating products that contain Cu.