EC and pH Chart: Target Values per Growth Stage for Hydro, Coco and Soil

EC and pH are the two numbers every grower checks daily. EC tells you how much fertilizer is in the solution; pH decides whether the plant can actually take those nutrients up. This chart gives practical target ranges per growth stage for hydro, coco and soil, plus an EC–ppm conversion table and a routine for reading input and runoff.

EC and pH in one minute

EC (electrical conductivity) measures the total amount of dissolved salts – your fertilizer plus whatever was already in the water. It is usually expressed in mS/cm. A higher EC means a stronger solution; it does not tell you which nutrients are present.

pH measures how acidic or alkaline the solution is. Each nutrient has a pH range in which it stays available to the roots. Outside that range, elements such as iron, manganese, phosphorus and calcium become harder to take up – even when they are present in the solution.

EC chart per growth stage

The values below are the total EC of the nutrient solution going to the plants, in mS/cm, including the EC of your source water. They are practical starting ranges for high-demand crops such as cannabis, not fixed rules.

In soil, part of the nutrition comes from the substrate itself, so feed solutions are usually a little weaker than in hydro or coco. In a pre-fertilised or living soil, young plants often need water only for the first weeks.

pH chart per growing medium

A pH that moves slowly within the range is normal and even helpful, because different nutrients are taken up best at slightly different pH values. A pH that keeps drifting out of the range points to a problem with the water, the substrate or the dosing.

How to use these numbers

• Start at the low end of each range and raise the EC gradually while watching the plants.
• Strong light, CO2 and a large root zone allow a higher EC; heat, low light and young or stressed roots call for a lower EC.
• Cultivars differ: some tolerate a strong feed, others show burnt leaf tips at the same EC.
• Dark green, clawing leaves and burnt tips suggest the EC is too high; pale new growth can mean it is too low.

Your water is part of the EC

Always measure the EC and pH of your source water first. Tap water with an EC of 0.5 leaves less room for fertilizer than reverse-osmosis water with an EC close to 0.0, and hard water with a lot of bicarbonate pushes the pH up after every correction. Our guide on how to read a water analysis explains which values matter and how to match your base nutrition to your water.

• Water analysis for growers: how to read EC, pH and your water report

Measure input and runoff

The numbers in a chart describe what you feed. What happens in the root zone shows up in the runoff (drain). In coco, rockwool and pots with soil, collect a sample of the runoff and compare it with the input:

• Runoff EC clearly higher than input: salts are building up. Irrigate with more runoff or lower the input EC slightly.
• Runoff EC lower than input: the plants are taking up more than you give. A small step up in EC is usually possible.
• Runoff pH drifting away from the input pH: check the water, the substrate buffer and the dosing before changing the feed.

Write the values down every day. A trend over several days tells you much more than a single reading.

EC, ppm and TDS conversion

Many meters show ppm (TDS) instead of EC. A ppm value is calculated from EC with a conversion factor, and meters use different factors – usually 500 or 700. Always check which scale your meter uses before comparing numbers.

Correcting pH the right way

• Add all nutrients first and mix well; adjust the pH last.
• If you use orthosilicic acid, add it to the water first, before the other products.
• Use pH-down (phosphoric or nitric acid) and pH-up (potassium hydroxide) in small steps, mix and measure again after each step.
• Re-check the pH of a stored tank after a few hours: it can still move, especially with hard water.

Keep your meters reliable

A chart is only useful if your readings are correct. Calibrate pH meters regularly with fresh calibration solutions, check EC meters against a standard solution, keep pH electrodes moist and clean, and measure at a stable temperature – most meters compensate to 25 °C.

Common mistakes

• Ignoring the EC of the source water.
• Correcting pH before all nutrients are in the tank.
• Raising EC because of a deficiency that is really caused by a wrong pH.
• Comparing ppm values from meters with different conversion factors.
• Measuring the input only and never the runoff.

Frequently asked questions

What is a good EC for cannabis in flower?

In hydro and coco, many growers work between 1.6 and 2.2 mS/cm at peak flower, and between 1.4 and 1.8 in soil. Start lower, watch the plants and the runoff, and adjust from there.

Why is the pH lower for hydro than for soil?

Without soil, there is no buffer and no soil life to help release nutrients. In a soilless system, a slightly lower pH keeps micronutrients such as iron and manganese available.

Do I need to adjust the pH in living soil?

Usually much less. A well-built living soil buffers the pH itself. Check the pH of your water and the runoff now and then, and correct only when the water is far outside the normal range.

Building your own feed line?

FertiQi produces base fertilizers, additives and stabilised orthosilicic acid – for your own grow, for resale or under your own label.

• Base fertilizers for hydro, coco and soil
• Stabilised orthosilicic acid
• Private label fertilizer production