There are several variables that a grower should watch out for - some are primary, such as temperature and humidity, and some are secondary, but they are also quite important. Today we will talk about the control and correct holding of EC values, ie the electrical conductivity of the solution, which is important especially for growers with hydroponic and therefore aeroponic systems.


Electric Conductivity (EC for short) is a term for the electrical conductivity of a solution. Thanks to the mineral salts that are present in fertilizers, but also in tap water and well water, we can recognize how many nutrients are in the water for watering or in the tank of the hydroponic system. In general, it can be said that thanks to the EC value, we can determine how many nutrients our nutrient solution contains. But nicely in order… 

Electrical conductivity (EC) is the potential of an electric current that is transported by water. It is also a designation of molar conductivity, which is denoted in siemens (S). This data defines how ions transport electrons. The higher the content of ions in water, the more electrons they transport, so the electrical conductivity is higher. 

In order to be able to imagine this physical phenomenon, we must set the uplifts from which this definition is reflected. 

Rain, demineralized and osmotic water have the lowest electrical conductivity. Ideally, this value has an EC value of 0.0 (0.0 mS / cm3). However, even the best DEMI or osmotic unit cannot purify the water completely clean, there is always a small deviation in the order of hundredths or thousands, which is not so important for cultivation purposes. 

The vast majority of growers use tap water, which always has an EC value, which depends on the location where you are. In the Czech Republic, in the vast majority of cases, the EC of tap water is in the range of EC 0.3–0.7, which are very nice numbers on a global scale. To give an idea of EC tap water in the coastal areas of Spain, it is in the range of EC 1-2, so growers there are forced to use osmotic units. 

Tap water, ie tap water, although it contains a certain EC value, does not have to contain elements that would be useful for plants in any way. It follows that a grower who uses his own fertilizers to feed plants is looking for water with the lowest EC value.

Many fertilizer producers have EC fertilization schemes in their plans. However, this value must be added to the inlet water value, so if the inlet water has an EC value of 0.5 and the recommended value is EC 2.0, we can only add nutrients with an EC value of 1.5 to the water. It logically follows that the smaller the EC inlet water, the more nutrients available to the plant can be added to the water. 

The EC value also varies depending on the stage of life of the plant. If the nutrients are excessive, the plants can burn, otherwise the plants are untened and show deficits. 

Again, it should be noted that each plant, species and variety can be very individual, but can be governed by the following criteria:

  • Cube buffering (non-rooted cuttings / clones) - EC up to 0.6
  • Rooted cuttings / clones in promotional medium - EC 0.5-0.8
  • Young transplanted plants - EC 0.8–1
  • Plants in the vegetation phase - EC 1–1.4
  • Plants in the flowering phase - EC 1,4–1,8
  • Plants in the ripening phase - EC 1.6–2.2 (even more, depending on the variety)
  • Plants before harvest - EC value as low as possible 

Of course, I also noticed extreme cases where the values in the flowering phase were even higher than 3.0 and the plants prospered beautifully, but it always depends mainly on the variety and the feeling of the grower. Therefore, each grower should mainly observe the behavior of plants, their leaves and petioles rather than the values on the device - so it is not possible to follow the tables or values recommended by the manufacturer, but above all in their own judgment. 

Too high EC in the early and later stages of plant life will cause burning, which is manifested mainly by burnt ends (tips) of leaves, which are brown in color and dry out. This is because the plant is unable to transpose enough water at an early stage, so the leaves do not cool and nutrients are stored in a quantity acceptable to the plant than is acceptable. 

The opposite of this phenomenon is deficit. Deficits of various elements are manifested by various spots on the leaves and petioles. However, most of the available fertilizers are adapted so that if there is a deficiency of an element, it is possible to supply the total fertilizer, either for growth or for flowering, to a greater extent, and thus get rid of the deficit. 

Deficits have various forms, which we will certainly talk about in future issues of our magazine, but the most basic are leaf fading (leaves are light green), red petioles (indicator of nitrogen deficiency) and stunted growth. 

A good way to combat nutrient deficiencies and surpluses is to gradually increase / decrease EC values, ie fluency. 

If the grower has the urge to shoot his EC values to the maximum level as soon as the plants start to show signs of flowering, it can never lead to a successful end. If the EC of the nutrient solution is raised gradually, the plants are able to absorb more nutrients than if this value were increased radically. Therefore, I recommend raising the EC by 0.1-0.3 every week - the result will be a plant that receives enough nutrients in sufficient quantities without suffering and there is also a much lower risk of fertilization. 

As for hydroponic growers, their work is much greater here. If the grower owns a hydroponic, aeroponic, flow or passive irrigation system, the EC values vary depending on how many nutrients the plants can absorb. For this reason, the adjustment of EC values is individual. 

The normal state in hydroponic cultivation is such that the EC gradually decreases with the water level, so the water is supplied at the same time as other fertilizers to maintain the set value. Be aware of growers whose water level in the tank is falling and the EC is rising instead of falling. This phenomenon is usually accompanied by a decrease in pH and means that the plants are unable to absorb the amount of nutrients in the water. The solution is to reduce the EC by 0.5 and then raise this value again weekly. 

EC control is also a welcome aid in the final phase of flowering and flushing when growing in soil and coconut, when the required output value is as small as possible. It is performed by pouring the pot over water without fertilizers, when the grower measures the water flowing from the pot. Coconut spillage is not as problematic as soil cultivation. This is due to the fact that when grown in earthy substrates, frequent watering can lead to overflow of plants, which is manifested by drooping leaves. In the worst case, the root mold, which can be indicated by a very strong odor from the pot and the growth of algae on the surface of the substrate. 

EC values are measured using electric EC meters. Unlike pH meters, these EC meters have a metal probe, so no storage solution is required for their maintenance. 

EC meters available on the shelves of Czech grow shops are divided into those that have digital or manual calibration. I always recommend the digital one, partly because they also have automatic temperature compensation, and in addition they do not risk breaking the device due to a bad, hasty calibration procedure. 

Calibration solutions for certain EC meters are mainly produced in two variants, namely 1,413 and 2,78. There is no two-stage calibration for EC meters, so always first find out which calibration fluid you need for a particular EC meter. If you are not sure, I have always been able to find this information by entering the device name into Youtube and looking at the video where the device type is calibrated. 

In some cases, EC meters for measuring electrical conductivity are also measured in PPM (parts per million) units. If you have such an EC meter and you want to convert PPM to EC, just divide the PPM by 500. For example, if you have a PPM of 1400 and divide by 500, you will get an EC of 2.8. 

In conclusion, I would like to add that by checking the EC, you are again a small step closer to truly professional cultivation, and each note in your growbook will make more sense. If you achieve a perfect result and have no notes on the cultivation process, it is very unlikely that you will repeat this success. That's why I advise you to write everything down! 


"In the Czech Republic, in the vast majority of cases, the EC of tap water is in the range of EC 0.3-0.7"

"With the EC control, you are again a small step closer to truly professional cultivation"

"With the EC control, you are again a small step closer to truly professional cultivation"

Photo: istock.com