The experimental setup consisted of eight wooden boxes (with dimensions
1.80 m × 0.80 m × 0.60 m) filled with soil. Four boxes were cultivated with tomatoes and four
boxes with chicory. For each type of plant, two boxes were filled with red soil and two with white soil.
In turn, for each type of plant and for each type of soil, one box contained plain soil, whereas the other
box contained soil with SAP. In each box, eight plants were planted. Figure 2a shows a schematization
of the disposition of the wooden boxes. Figure 2b shows a picture of the experimental setup.