EC stands for Electrical Conductivity (mS/Liter) and is used to measure the amount of (usable and unusable) salts in water.
Plants that grow and bloom quickly must have enough nutrients available.
To measure the nutrient value (actually the nutrient salts), you use an EC meter. The EC meter simply measures the electrical resistance in water, which is why a medium like soil must be moist when tested.
An EC meter measures the total sum of all salts.
An EC of 0.1/100L from one nutrient brand does not necessarily mean the same nutrient value as 0.1/100L from another brand.
Most cheaper plant foods contain many elements such as chloride, cadmium, and other heavy metals. The EC meter measures these elements too.
Growers who cultivate by weight try to make the plant absorb as many nutrient salts as possible to achieve a heavier end result. These nutrient salts must be available and absorbable, and preferably balanced to stimulate uptake.
The best way to measure this in NFT systems is to extract some water from the medium with a syringe and then test it.
In hydroponic systems with a medium like rockwool, it is best to push the EC meter directly into the wet rockwool.
For soil or coco, it is best to mix the medium lightly with demi-water in a cup and measure after soaking. With normal tap water, this is not possible, since it also includes the EC of the water itself.
Demi-water can be purchased at any gas station as battery water.
How much EC for plants?
Clear target values for the amount of nutrient salts in a solution are difficult to give.
EC depends on factors such as plant size, water quantity, drip frequency, lighting, natural EC of your tap water, temperature, humidity, and plant type.
All of this determines how much water and nutrients a plant needs.
The grower’s preference also plays a role. Some growers achieve great results with a “strong” nutrient solution, while others succeed with a “weak” solution.
In general, a nutrient solution for young plants has an EC of 1.0 to 1.3 mS, which can increase to 2.0 mS for mature plants.
If the “natural” EC of tap water differs greatly from the average values assumed by fertilizer brands (around 0.5–0.6), this difference must be corrected.
Example:
Grower A measures an EC of 0.5 in his tap water.
He wants an EC of 1.8, so he adds 1.3 EC from nutrients.
Grower B has harder water with an EC of 0.8. If he also wants an EC of 1.8, he only adds 1.0 EC from nutrients. That is 0.3 EC less than Grower A.
To deliver the same nutrients as Grower A, Grower B must aim for an EC of 2.1.
You can also assume that the EC in the root zone may be half a point higher than in the drip water.
The EC level is also linked to the number of drips.
A relatively high nutrient solution, for example with an EC of 2.7, spread over five drips of 500 ml per plant, causes fewer problems in the root zone than one drip of 150 ml six times a day per plant.
In the latter case, the nutrient salts in the solution evaporate, causing the EC in the root zone to rise significantly. Those who prefer frequent drips should use a weaker nutrient solution.
In all cases, you must know what the nutrient solution is doing in the medium. Therefore, depending on the system, check the pH and EC of the drain water or directly in the medium every 2 days.