EC is a signal, not a nutrient recipe.

Electrical conductivity reflects the solution's ability to conduct electricity. In a nutrient tank it is a useful estimate of total ionic strength, but it cannot identify individual nutrients or prove that their ratios are appropriate. A stable EC can coexist with selective uptake, sodium or chloride accumulation, or a formulation error.[1][2]

pH influences nutrient availability, but it also does not reveal composition. Treat pH and EC as fast operating signals that tell you when to investigate, not as a complete laboratory analysis.[1]

Analyze source water before building a nutrient program. Alkalinity, baseline EC, and specific ions affect acid demand, formulation, and what can accumulate in a recirculating system. Use a crop- and stage-appropriate formulation from a qualified source, follow the product's mixing order, and verify chemical compatibility before combining concentrates.[1][2][3]

Record the active reservoir volume, water source, formulation and batch, concentrate lots, additions, water temperature, and the instrument used. Without those facts, an EC correction is difficult to reproduce or audit.

Interpret EC together with reservoir volume and water use. If water falls while EC rises, concentration may be outpacing nutrient removal. If both water and EC fall, crop uptake and dilution may be moving differently. Those are hypotheses, not automatic dosing commands; crop stage, weather, leaks, meter condition, and source water still matter.

• Calibrate and maintain pH and EC instruments to their manufacturers' instructions.
• Measure at a consistent, well-mixed location and comparable time.
• Record reservoir volume, additions, drain or replacement, temperature, pH, and EC.
• Inspect roots, emitters, return flow, and representative plants when the trend changes.
• Escalate persistent or unexplained imbalance to water, solution, or tissue analysis.

Recirculation saves water and nutrients, but repeated top-up does not guarantee the original ratio remains intact. Establish a replacement or partial-replacement decision based on the crop, source water, formulation, analytical evidence, discharge obligations, and system behavior. Avoid presenting a fixed calendar interval as universal.[2][1]

Plan where discharged solution can legally and responsibly go. Nutrient solution is an input inventory and a waste stream; the record should show both.

A good reservoir record lets another grower reconstruct the starting water, formulation, additions, crop demand, instrument condition, and decision that followed. That is what turns EC from a dashboard number into evidence.