# EC and ionic balance
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Temperature-corrected conductivity, individual-ion drift and the limits of EC-only nutrient control.
In brief
Temperature-corrected conductivity, individual-ion drift and the limits of EC-only nutrient control.
## Explanation
EC measures how well the solution conducts electricity. It is useful for detecting overall dilution or concentration, but it cannot state how much potassium, nitrate, calcium or magnesium is present individually.
EC-1 E C 25 ≈ E C T 1 + α ( T − 25 ) \mathrm{EC}_{25}\approx\frac{\mathrm{EC}_T}{1+\alpha(T-25)} EC 25 ≈ 1 + α ( T − 25 ) EC T Approximate temperature correction to 25 °C; α must match the solution or instrument model.
**Explanation**Measured conductivity is corrected to 25 °C so readings taken at different temperatures can be compared.
## Ion drift
Plant uptake is selective. A controller can hold bulk EC near target while individual ions diverge. This is directly documented in hydroponic nutrient-dynamics research. [R17]
## Required controls
- known initial elemental composition;
- logged stock additions and water additions;
- reservoir-volume accounting;
- periodic solution replacement or laboratory verification;
- crop-specific tissue or solution analysis for research claims;
- EC used as a bulk constraint, not an ion sensor.
## EC experiment rule
An EC treatment is reproducible only when the recipe used to reach that EC is also specified. Raising EC with a balanced nutrient concentrate is biologically different from raising EC with NaCl or a single salt, even when the meter reads the same value.
## References
- [R17] Vought, Kelsey; Bayabil, Haimanote K.; Pompeo, Jean; Crawford, Daniel; Zhang, Ying; Correll, Melanie; Martin-Ryals, Ana (2024). Dynamics of micro and macronutrients in a hydroponic nutrient film technique system under lettuce cultivation. *Heliyon*. https://doi.org/10.1016/j.heliyon.2024.e32316