Porous substrate with an acid increasing effect on the culture
Pumice is a volcanic product that is released on volcanic eruptions. The material originates from countries like Iceland and Germany. During a volcanic eruption, glowing alkaline material is flung away and it solidifies in the air. As a result, air bubbles are closed in, which causes that the material gets a porous structure. In some cases pumice is excavated under former arable land. In that case, the material must first be processed to make it suitable for application in horticultural substrates. The source is decisive for the porosity and the bulk density. Pumice from Germany is normally less porous and more heavy than pumice from Iceland. Pumice is produced in various fractions.
Germany and Iceland.
Pumice is suitable as raw material in potting soil and as pure substrate. A well-known application was the bucket culture of cucumber. During the culture the material erodes a little, influenced by a sour root environment. Pumice has a pH increasing effect on the culture.
Because pumice is excavated, there is a specific control on the production process, especially to avoid contamination with weeds and nematodes. Also element contents and the contents calcium carbonate form important quality parameters.
