pH value

The pH value indicates how acidic or alkaline the irrigation water or nutrient solution is. It is measured on a scale from 0 to 14: values below 7 are acidic, above 7 are alkaline, and exactly 7 is neutral. In cultivation, the pH value is one of the most important factors, as it helps determine whether a plant can absorb the available nutrients at all.

What the pH value does

Each nutrient is only well absorbed by the roots within a specific pH window. If the value is outside this range, the plant cannot utilize the available nutrients, even if they are present in the substrate – this is referred to as a "nutrient lockout." The insidious thing is that the plant shows deficiency symptoms even though it has been fertilized sufficiently. Checking the pH value first when problems arise often saves a lot of guesswork.

Reference values and measurement

The target values depend on the cultivation method. In soil, the ideal range is usually between approximately 6.0 and 7.0. In hydroponics or on coco, it tends to be lower, often between 5.5 and 6.5. Measurement is done with a digital pH meter or with drop tests. If the value is too high or too low, it can be adjusted with pH-down or pH-up products. Closely related is the EC value, which measures nutrient concentration.

Frequent questions about pH value

What is the ideal pH value?

In soil, about 6.0–7.0; in hydro and on coco, rather 5.5–6.5. The exact target value depends on the substrate.

Why does my plant show deficiency symptoms even though I fertilize?

It is often due to the pH value. If it is not correct, the plant cannot absorb existing nutrients – despite fertilization.

How do I measure the pH value?

With a digital pH meter (calibrate regularly) or with a drop test. Digital devices are more accurate and faster.