*2.3. Sample Collection and Preparation*

Soil samples were collected from the R'mel agricultural area within the Loukkos perimeter located in the northwest of Morocco between the city of Tangier and Rabat. The samples were taken from three agricultural fields cultivated for potatoes and strawberries. The three chosen cities were recently fertilized. The sampling was carried out manually using a shovel at a level between 0 and 30 cm from the surface of the fields. For each of the three sites, a quantity in the order of 5–8 kg was taken. The samples were dried, sieved to 2 mm, and preserved immediately at a temperature below 4 ◦C in polyethylene plastic bags.
