Runoff EC
The electrical conductivity of drainage water collected after irrigation. Runoff EC helps growers detect salt buildup, overfeeding, and changes in substrate nutrient concentration.
Runoff EC is the electrical conductivity of the drainage water that leaves a container, slab, or substrate after irrigation. It is measured in mS/cm and gives growers a practical view of how concentrated the root zone solution has become between feeds.
In indoor cultivation, runoff EC is usually compared with the input EC of the nutrient solution. If runoff EC is much higher than input EC, salts may be accumulating in the substrate because the crop is taking up more water than nutrients or because drainage is too low. If runoff EC is much lower than input EC, the crop or substrate may be using nutrients faster than expected.
Common uses:
- Checking whether the feed strength matches plant demand
- Detecting salt buildup before visible stress appears
- Deciding when to increase drainage or adjust irrigation volume
- Comparing different zones, benches, or irrigation events
Runoff EC should be interpreted together with runoff pH, drainage percentage, substrate moisture, and plant condition. A single reading is less useful than a trend measured at the same point in the irrigation cycle.
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