ISO 5311:1992

Specifies two methods for dry fertilizers only: the machine-tapping method and the hand-tapping method. Its principle is pouring the fertilizer from a specified funnel into a specified measuring cylinder of known volume, tapping the cylinder by means of a tapping machine or the walls of the cylinder by hand, and weighing the contents of the cylinder. If the fertilizer has absorbed moisture during transport or storage, it is necessary to dry it in an environmental chamber.