In cannabis cultivation, EC, or electrical conductivity, is a crucial parameter. It indicates the concentration of the nutrient solution and significantly determines whether plants can effectively absorb nutrients. Inadequate control of EC can lead to nutrient problems, stunted growth, or root damage.
- What is EC?
EC stands for electrical conductivity and measures the amount of dissolved salts in water. In cannabis cultivation, these salts are usually fertilizers (macro- and micronutrients).
High EC: many dissolved nutrients, strong concentration.
Low EC: few nutrients, weak concentration.
Cannabis roots absorb nutrients best at an optimal EC that suits the growth stage and medium.
- Ideal EC values per growth phase
The required EC varies depending on the growth stage and the medium.
In earth:
Seedling: 0.6–0.8 mS/cm
Vegetative phase: 1.0–1.2 mS/cm
Flowering stage: 1.2–1.8 mS/cm
In coco or hydro (more direct absorption):
Seedling: 0.8–1.0 mS/cm
Vegetative phase: 1.2–1.6 mS/cm
Flowering stage: 1.6–2.0 mS/cm
Note: with hydro and coco the margin is smaller, because roots are in direct contact with the medium and too high EC quickly causes damage.
- Why EC is important
Nutritional efficiency
A correct EC ensures that plants can absorb all the necessary macro and micro nutrients.
Preventing nutritional deficiencies
Too low an EC can lead to slow growing plants, yellowing leaves or lack of flowering.
Preventing burns or salt build-up
Too high an EC can damage roots, burn leaves and block the uptake of new nutrients.
Control over the growth cycle
By adjusting EC per growth phase, growers can stimulate vegetative growth or flowering and optimally nourish the plant.
- How to measure EC
Use a digital EC meter for accurate measurement.
Always measure the EC of the nutrient solution before watering.
Also check the drainage water to see what the roots are actually receiving.
Tips:
Calibrate your EC meter regularly.
Measure at a constant temperature (ideally 20–25°C) for accuracy.
- Adjust EC
Too low EC:
Add additional nutrients at the recommended dose for the growth stage.
Too high EC:
Dilute the solution with pH-adjusted water.
If necessary, rinse the medium to remove any accumulated salts.
Important: Adjust EC gradually to avoid root shock or stress.
- Common mistakes
Under-measuring: plants appear healthy but develop hidden deficiencies.
Too high EC in hydro: roots burn quickly and lead to growth stagnation.
Insufficient attention to drainage water: EC in the pot can be higher than the nutrient solution, causing salt buildup.
Do not adjust per phase: the same EC during seedling and flowering is suboptimal.