EC is the most useful number in your grow. Here is what it means and how to act on it.
EC stands for electrical conductivity. It measures the concentration of dissolved minerals in your water. The higher the EC, the more minerals are present.
You need to understand three things: what EC to target, how to measure it, and what to do when the number is wrong.
EC targets by stage
Targets change as your plant moves through its cycle. They increase as nutritional demand increases, then drop sharply at flush.
Soil
| Stage | EC target |
|---|---|
| Growing stage | 0.6 – 1.2 |
| Start of flower | 1.2 – 1.5 |
| Mid flower | 1.5 – 1.8 |
| Mid / end of flower | 1.8 – 2.2 |
| Flush | 0.0 – 0.4 |
Coco, hydro, and aqua
| Stage | EC target |
|---|---|
| Growing stage | 0.8 – 1.2 |
| Start of flower | 1.2 – 1.6 |
| Mid flower | 1.6 – 2.0 |
| Mid / end of flower | 2.0 – 2.4 |
| Flush | 0.0 – 0.4 |
These targets assume source water with a starting EC of 0.3. If your tap water is significantly higher, account for it before adding nutrients. Running a hydroponics system? Add 0.2 EC to each stage. Inert mediums do not buffer the way soil does.
How to measure EC
You need an EC pen. They are inexpensive and accurate enough for home and small commercial use. Calibrate once a month. A drifting pen gives false confidence.
- Measure your feed water after mixing nutrients.
- Measure your runoff.
- Compare the two numbers.
If runoff EC is significantly higher than feed EC, the medium has accumulated salts. Flush and reduce your dose. If runoff EC is lower, the plant is hungry. Increase dose slightly at the next feed.
When the number is wrong
The plant is underfed. Growth slows. Leaves may pale. Move toward the upper end of the target range and monitor over 48 hours.
The plant is overfed. Tips may burn or curl under. Flush with plain water at low EC (0.0 to 0.4) and return to the lower end of the target range.
Check pH. Nutrient lockout caused by incorrect pH mimics deficiency symptoms even when EC is correct. Soil should sit between 6.0 and 7.0. Coco and hydro between 5.5 and 6.5.
EC is a number that tells you whether you are feeding correctly. Check it every feed. Adjust when it is out of range. The rest is watching the plant respond.
See the full Berkana dosing schedule for EC targets by stage and medium.