Soil samples collected in the study area are placed in a plastic bag on site, sealed and labelled with a unique sample label. After sample storage, some pre-treatments have to be carried out before the physico-chemical investigation. Pre-treatment includes sample splitting, drying, sieving (< 2 mm for fine soil, see Soil Laboratory - Particle Size Analysis) and digestion. The sample is divided by a riffle divider or by quartering to the desired quantity. The samples are either dried in air …