Pripravo končnega vzorca, prejetega v laboratoriju, sestavlja skupina postopkov, ki navadno vključujejo presejanje, mletje in mešanje, opravijo pa se tako, da: je po eni strani tudi najmanjša stehtana količina, določena s temi analitskimi metodami, reprezentativna za laboratorijski vzorec, po drugi strani drobnost delcev gnojila ne more biti spremenjena tako, da bi znatno vplivala na topnost v različnih ekstrakcijskih reagentih.
The preparation of a final sample received at the laboratory is a series of operations, usually sieving, grinding and mixing, carried out in such a way that: - on the one hand, the smallest amount weighed out laid down by the methods of analysis is representative of the laboratory sample, - on the other hand, the fineness of the fertilizer cannot have been changed by the preparation to the extent that its solubility in the various extraction reagents is appreciably affected.