The soil will collect from the ground in bags and cleaned from plastic, wood, tree roots, stones, brick pieces etc. dried in sun to such an extent that it can be broken by wooden hammer.
Theocharopoulos, S. P., Wagner, G., Sprengart, J., Mohr, M. E., Desaules, A., Muntau, H., ... & Quevauviller, P. (2001). European soil sampling guidelines for soil pollution studies. Science of the total environment, 264(1), 51-62.