Electrical conductivity of the solution – EC

The correct concentration of mineral salts in the nutrient solution is essential for the healthy development of plants and is one of the most important variables a grower needs to monitor during the cultivation cycle. This concentration is given by the EC (Electric Conductivity) value. How do we measure it and which values are best for a juicy harvest?

From the electrical conductivity of the solution we can easily tell the amount of nutrients in the water used for irrigation or in the reservoir of hydroponic systems. For hydroponics or possibly aeroponics the correct concentration of salts present in fertilizers, as well as in tap or well water, is absolutely crucial...

Electrical conductivity can also be described as the potential for an electric current to be carried by water. There is no need to go into detailed physical definitions; for the pleasure of growing it is enough that we can imagine this physical phenomenon and learn to work with it.

In cultivation practice the most commonly used water is ordinary tap water. The EC of tap water depends primarily on the location. Within the Czech Republic it ranges from about 0.3 to 0.7. That is not a given everywhere, so Czech growers have reason to be happy. By comparison, there are many areas abroad where tap water commonly has EC values in the 1–2 range. The lower the EC of the water itself, the better, because water as such is not yet the main source of nutrients for cultivated herbs, flowers and crops. We supply nutrients via fertilizers. When fertilizing, it is therefore necessary not to overlook the EC of the incoming water. To give a clear example: if we have a predefined recommended EC for fertilization of, for example, 1.9 and we know that the water we use has an EC of 0.6 on its own, we can only enrich the water with nutrients to an EC value of 1.3. The key point is that it is good to have water with as low an electrical conductivity as possible. The lower the EC of the water, the more nutrients we can provide to the plants using fertilizers. An excess of nutrients can burn your crop and is therefore just as harmful to plants as their deficiency. When fertilizing, continuity is important. Experienced growers prevent excesses and deficiencies of mineral salts by gradually increasing or decreasing EC values, for example each week by 0.1 to 0.3. This way plants are much better able to absorb the nutrients contained in the fertilizers than with a sudden jump in doses. Avoid over-fertilization!

Values shown on the display of a pocket digital EC meter

The EC value is not stable and changes throughout the plants' life stages. It should be emphasized that plants' needs are individual and depend greatly on the species and variety. With that caveat we can specify recommended values as follows:

• Young plants: EC 0.6 – 1.2
• Older and larger plants: EC 1.2 – 2.5

To measure and maintain optimal values we can use EC meters. Unlike pH meters, they usually do without maintenance solutions and are equipped with a metal probe. In terms of calibration there are devices on the market that allow digital or manual calibration. Nowadays, however, the vast majority of growers use the digital variant, which is also very advantageous for beginners, because automatic temperature compensation prevents malfunction due to incorrect calibration procedure. EC meters are indispensable, among other things, during the flowering phase and also when flushing. On Higarden.cz you can also find replacement probes or practical measurement sets. Calibration solutions for EC meters are mainly produced in the 1.413 and 2.78 mS variants. Solutions labeled 2.8 are intended for the same use as 2.76, so don't be misled—the difference is only rounding.

An economical EC meter option from Milwaukee

In conclusion, one thing is tables and recommended values, but observation of your plants is just as important as measurement accuracy. With attention and growing experience you will soon recognize on stems and leaves whether they are at risk of over-fertilization and burning or are instead suffering from nutrient deficiency. We hope they will thrive under your care and that both the products available on our e-shop and the advice in this article will help you with that. If you are interested in anything else, we welcome your questions sent to the usual address info@higarden.cz.

• Digital EC meter
• EC meter
• Measurement sets