STEP Systems
STEP Systems News
May, 2021

Salinity measurement

Conductivity vs. Activity
EC measurement
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.

AM measurement
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.
Conductivity measurement
EC 5000
for solutions

Conductivity measurement for salinity determination of liquids and solutions. The measuring range up to 200 mS even allows precise measurements of fertilizer stock solutions.
More info (item 10290) →
AM 5000
for soil / substrates

Direct measurement of soil salinity taking into account the relevant soil properties, like soil moisture, temperature and soil compaction.
More info (item 10190) →
EC + AM 5000
for all growing medias

AM-measurement of salinity directly in the soil (activity) and conductivity of nutrient and stock solutions with only one device. Optimal configuration for:
  • peat or any other substrate production and composting facilities, production of any growing media
  • cultivation of ornamental plants particularly with subirrigation systems
  • cultivation of any nursery plants, particularly if slow release fertilizers are applied
  • basically for all growers using a solid growing media and liquid fertilization system
EC and AM values

The COMBI 5000 manual provides tables with recommended pH and salinity values for all common plants according to their nutrient demands. For quick check use our COMBI 5000 App.
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90451 Nuremberg
Tel.: +49 911 96 26 05 0
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