# Input EC

> Input EC is the electrical conductivity of the nutrient solution going into the pot or system, in mS/cm, including the base EC of the source water.

- Canonical: https://genetixbay.com/knowledge/glossary/input-ec.html
- Also written: feed EC, EC in, inflow EC, reservoir EC, feed strength
- Glossary category: pH, EC and water · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

Input EC (feed EC) is the [conductivity](https://genetixbay.com/knowledge/glossary/ec.md) of the solution you actually apply: source water plus nutrients plus any [pH](https://genetixbay.com/knowledge/glossary/ph.md) adjusters. It is the dose. It is measured after mixing and pH adjustment, at 25 °C or with [temperature compensation](https://genetixbay.com/knowledge/glossary/atc.md).

## In practice

Always know your base water EC. Tap water at 0.5 [mS/cm](https://genetixbay.com/knowledge/glossary/ms-cm.md) plus 1.2 mS/cm of nutrients gives an input EC of about 1.7 mS/cm, but 0.5 of that may be sodium, chloride and bicarbonate that are not useful to the plant. With [RO water](https://genetixbay.com/knowledge/glossary/ro-water.md) at 0.02 mS/cm, nearly all the EC is nutrient. Two growers following the same chart can therefore deliver quite different nutrition.

Track input and [runoff](https://genetixbay.com/knowledge/glossary/runoff.md) EC together. Input EC is what you control; runoff EC tells you how the plant and medium responded. Hershkowitz, Westmoreland and Bugbee (2025) found that raising nutrient concentration beyond moderate levels did not improve yield or [cannabinoids](https://genetixbay.com/knowledge/glossary/cannabinoid.md), so a stable, moderate input EC with steady runoff is a sound default.

## Don't confuse with

- **Runoff EC**: what drains out.
- **Additive EC**: the EC added by nutrients alone (input minus base water), which some charts quote.

## Related terms

[Runoff EC](https://genetixbay.com/knowledge/glossary/runoff-ec.md), [EC](https://genetixbay.com/knowledge/glossary/ec.md), [RO water](https://genetixbay.com/knowledge/glossary/ro-water.md), [Tap water](https://genetixbay.com/knowledge/glossary/tap-water.md)

## Read more

- [Runoff testing: how to measure root-zone pH and EC and what the numbers mean](https://genetixbay.com/knowledge/ph-ec/runoff-testing.md)
- [Building a cannabis feed by stage: ppm targets per element and how to hit them](https://genetixbay.com/knowledge/nutrients/feed-by-stage.md)

## Sources

1. Hershkowitz JA, Westmoreland FM, Bugbee B. 2025. Elevated root-zone P and nutrient concentration do not increase yield or cannabinoids in medical cannabis. Frontiers in Plant Science 16:1433985. https://doi.org/10.3389/fpls.2025.1433985
2. Cavins TJ, Whipker BE, Fonteno WC, Harden B, McCall I, Gibson JL. Monitoring and managing pH and EC using the PourThru extraction method. NC State University Horticulture Information Leaflet 590. Cited via MSU Extension: https://www.canr.msu.edu/uploads/resources/pdfs/measuring_ph_and_ec_of_crops_grown_in_large_containers.pdf