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How to check the pH-value of water?

pH value water checkEvery cultivation is dependent on water. Whether water is suitable to be administered to a crop, depends on the pH-value of the water. The pH-value indicates the acidity of a solution. But how to check the pH-value of water? Our specialist will explain in this article.

Properties of suitable water

In general, proper supply water contains a low sodium content. If you have a soil-bound cultivation, often a sodium content of 0.5 mmol/l is used. By contrast, the sodium content in case of non-salt sensitive cultivations is allowed to be higher. Proper water in general has a pH-value between 4.5 and 6.0. If a lower pH-value is used, then there is a chance that the substrate and the roots will get damaged. Too high values on the other hand, may lead to a reduced availability of trace elements. The presence of bicarbonate in the water ensures that the pH in the substrate increases. Therefore, it is hard to direct the pH-value in the root environment. For this reason, it is important to neutralize the major part of bicarbonate by use of acidic fertilizers. 

Tip: the quantity mmol/l of bicarbonate equals the quantity mmol/l of nitric acid. 

Checking the pH-value of water

The pH-value of the water can be measured by use of a pH meter. The measuring of the pH-value of the water is done by following step-by-step plan: 
  1. Put the solution to be measured in a clean beaker or measuring glass and determine the temperature.
  2. Rinse the probe of the meter with demineralized water and clean it with a tissue. Then place the probe in the solution to be measured and stir for a moment.
  3. Set the temperature of the solution using the left rotary knob on the meter.
  4. Wait 1 minute until the probe is stable.
  5. You can now read the pH-value of the water.
  6. Finally rinse the probe again with demineralized water and place it back in the meter holder. 
Please note: there must always be some quantity of Probe care present in the holder, as this ensures the preservation of the probe. If the probe is connected, the meter should indicate a pH-value of approximately 4. If the pH is higher than 5, then replace the Probecare in the tube. It is important to regularly calibrate the pH meter.

pH-value per cultivation

The pH-value of water may vary per cultivation in substrates or different soil types. Below, the guidelines per type of cultivation are shown.

Soil typeGuidelinespH-value
  • Put a sample in a well cleaned pot;
  • For recirculation systems the outgoing water can be sampled;
  • In case of Rockwool substrate and synthetic foams, take samples in approx. 20 places
< 4,5 too low
4,6 - 5,3 fairly low
5,4 - 6,1 normal
6,2 - 6,9 fairly high
>7,0 high

Peat substrates and potting soilMMeasure a mixture of 1-part volume of peat/potting soil and 2-part volumes of demineralized water. After shaking of the mixture, the pH-value can be measured directly.< 3.9 very low
4.0 - 4.7 low
4.8 - 5.5 fairly low
5.6 - 6.3 normal
6.4 - 7.1 fairly high
>7.2 high

Greenhouse soilpH-values in greenhouse soil is more difficult to measure because these are dependent on the carbonated lime content, organic matter content and the way in which the deposition took place. For that reason, there are some guidelines for certain soil types.A. Sand pH
5.0 - 5.4 low
5.5 - 5.9 fairly low
6.0 - 6.4 normal
6.5 - 6.9 high

B. Clay
5.5 - 5.9 low
6.0 - 6.4 fairly low
6.5 - 6.9 normal
7.0 - 7.4 high

C. Peat
4.0 - 4.4 low
4.5 - 4.9 fairly low
5.0 - 5.4 normal

To be used for a proper pH-value

Product specialists pH value

More information about the pH-value of water

Do you have any questions about the measuring of the pH-value of water, or would you like customized advice? Then contact one of our fertilizer product specialists, or ask your question using the form below. We will then contact you as soon as possible, even within 24 hours on working days.

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