Hydroponic Crop EC / pH Reference Chart
Sourced target EC and pH ranges for 7 common hydroponic crops.
| Crop | Target EC (mS/cm) | Target pH | Note |
|---|---|---|---|
| Lettuce | 1.2–1.8 | 5.6–6.5 | pH sources disagree: extension guides cite 6.0-7.0, Cornell's commercial handbook cites 5.6-6.0. Lean toward the lower half for long-running systems. |
| Spinach | 1.8–2.3 | 6–7 | Reflects vegetative growth; not broken out by growth stage. |
| Basil | 1–1.6 | 5.5–6 | Sensitive to EC above this range — favor the low end for cuttings and young plants. |
| Tomato | 2–3.5 | 6–6.5 | Spans early growth (~2.0) to flowering/fruiting (2.4-3.5+) — raise EC as the plant matures rather than holding one fixed number. |
| Pepper | 0.8–1.8 | 5.5–6 | Reflects early growth; many growers raise EC toward 2.0-2.5+ once fruit set begins. |
| Cucumber | 1.7–2 | 5–5.5 | Some growers run cucumber higher (up to ~2.5) during heavy fruiting. |
| Strawberry | 1.8–2.2 | 6 | Source cites a single pH value (6.0) rather than a range. |
Use these ranges with the nutrient dosing calculator to find your total target meter reading after accounting for your source water.
Frequently asked questions
- Where does this data come from?
- Primarily Oklahoma State University Extension's "Electrical Conductivity and pH Guide for Hydroponics" fact sheet, cross-corroborated for lettuce against University of Florida IFAS, for tomato against Ohio State University Extension, and for lettuce pH additionally against Cornell's CEA lettuce handbook. WebFetch to the primary documents wasn't available while building this, so figures came from search-result synthesis and a domain-expert review rather than reading every source document directly — see this project's docs/domain-reference.md for the full review, including where sources genuinely disagreed, and lib/hydroponic-ec-reference.ts's header comment for per-crop citations.
- Why might my nutrient brand's feeding chart give different numbers?
- Commercial nutrient lines (General Hydroponics, Masterblend, and others) tune their own feeding charts to their specific formulations and target ranges, which can reasonably differ from these general extension-sourced ranges. Treat this chart as a starting reference, not a replacement for your nutrient brand's own guidance.
- Why is there only one EC range per crop instead of one per growth stage?
- Growth stage is genuinely the biggest factor in target EC — young/seedling plants tolerate much less than mature, fruiting plants of the same crop — and this chart doesn't yet break ranges out by stage. Where a source specifically noted this (tomato, pepper, cucumber), the per-crop note says so; treat the low end of a range as safer for young plants and the high end as more appropriate once a crop is established or fruiting.