Salinity is determined by the concentration of total dissolved salts. In water and/or suspensions, salt ions are completely free and mobile and can be measured by means of electrical conductivity (EC): the higher the electrical conductivity, the higher the salt concentration.
Is EC the same as soil salinity?
Basically it is important to know that there is no EC measurement directly in the soil possible because not all salt ions are dissolved and thus cannot be taken up by the roots. This is why we do not call salinity measurement directly in a substrate or soil “EC measurement”, because it can take place only in a solution, even though the expression "EC measurement in soil" is used colloquially.
When measuring salinity directly in the soil or substrate, we refer to the term "activity measurement", used by its developer Prof. Dr. Tepe from the German Geisenheim University. This method measures only the amount of dissolved or available for the plant salts, which are “active” under current conditions in the soil such as moisture, density and temperature and can be absorbed by the roots. Our AM probe measures only those plant-available salts directly in the soil/growing media.