How to measure the EC values?

Hoe de EC-waarden meten? - KWEEK
Because user-friendly EC meters are easily and cheaply accessible everywhere, everyone can easily measure the salt concentration (i.e. the amount of ions) of plants in pots, the soil in the greenhouse or garden, the compost, new or reused potting soil, pond, rain, soil or tap water and so on. But how should you measure correctly and how can you evaluate the figures? An important aspect is the temperature of the measuring water. In addition to measuring the soil, you can also measure the water quality of rain, pond, well and tap water with the EC meter.

The temperature of the measuring water influences the results of the measurement. It is therefore necessary to always measure at the same temperature in order to compare the measurement results. Results that you can find in the literature are based on a water temperature of 25 ° Celsius. Per 1 degree temperature difference, the EC value will indicate 2.5% higher or lower.

By knowing the EC value of the soil, we also learn more about the growth potential of the crops. After all, if the EC value in our soil becomes too high due to the addition of fertilizers, the growth of the plants will be inhibited. This results in a lower yield, less root development, less leaf growth and reduced flowering.

Sometimes it can be useful to increase the EC value. You must at least know what you are doing and have access to an EC meter. Of course you will always have to stay within the acceptable growth norms. Increasing an EC value that is too low can, for example, promote generative growth, for example in plants that have a lot of greenery and have too few flowers, or to stimulate flower buds in fruit crops. The leaf color can also be influenced. When cultivating container plants, the EC value can be adjusted to harden the plants and thus make them less sensitive to frost. In cut flower cultivation, flowers grown at a higher EC value will have a better shelf life.

Take soil samples yourself


  • EC measuring device
  • For outside 10 plastic pots
  • distilled water
  • stick to stir


Grab a bit of coconut or soil from the pots near the plants. Do you want to measure in the garden? Then take a few soil samples at different places in the conservatory or in the garden and at different depths (up to 50 cm). Put the small, the same amount of soil in different pots. The more samples you take, the better and more accurate the image of the EC value will be. I would recommend taking 10 samples anyway.

Add the same amount of distilled water to all jars and mix well with a stick or spoon. Do not use rainwater or tap water because they themselves also contain an amount of ions that will cause your measurement to give an incorrect picture. Distilled water has been stripped of salts and minerals and is also used to fill car batteries.

It is also useful to first do the pH value with your pH meter of the various measurements. A PH measurement indicates the acidity in your growing medium, look further on the site for this.

A guideline for average good values

normal garden soil 3-5
universal potting soil 4-7
sowing and cutting soil 1.5-2
moorland 2.5
pond soil 1.5
box ground 4
cacti and succulents 5
cultivation of lettuce 1-1.8
cultivation of tomatoes 1.2-1.8
nursery crops 2.5
less salt sensitive crops 4-5
green compost and homemade compost 7.5-15
hydroponics 1.2-1.5
flush greenhouse 0.5-1.0
growing on grodan rockwool 1.2-1.5

Measure water quality

When we measure different types of water, we can see surprising differences: rainwater contains 1/10 less salts than groundwater:

water type EC value in mS/cm:

rainwater 0.01 - 0.05
well water 0.1 - 0.5
tap water 0.3-0.7


Take several samples of the water you want to measure, for example the quality of your rainwater. Put the small, the same amount of water in different jars. The more samples you take, the better and more accurate the image of the EC value will be. I would recommend taking at least 3 water samples.

First check and, if necessary, record the pH value of the various samples with your pH meter. See the article about measuring the pH for this. Check the temperature of the different jars with your EC meter and wait until they are the same if necessary.

First check and record the EC value of the various samples with your EC meter. Assessment of the water quality measurement results in mS/cm (see part 1 for the meaning of this)

in mS/cm quality

< 0.25 very good water which is suitable for all crops
0.25 to 0.75 good water which is suitable for more or less salt tolerant plants.
Flushing regularly and measuring the EC value will be necessary
> 0.75 water that is poorly suited, possibly usable if it can be flushed thoroughly every year