Definition: Internal surface area of soil clays

It is expressed in m²/g. This is the surface area of all the layers that make up a clay. Nutrient ions in the soil are stored between the layers, so the larger the internal surface area of a clay, the more ions it will be able to retain and the greater its fertility. High internal surface areas are more suited to large red wine terroirs. Low internal surface areas are more suitable for the production of white wines.