The pH in the root environment plays an important role in the absorption of nutrients. Especially when it comes to the absorption of N nutrients, such as NH4+ or NO3. For optimal absorption of nutrients, the pH in the root environment should be about 5.
A professional grower measures watering pH and drain pH, but drain pH only gives an average pH with respect to what has happened in the substrate and as such does not show what is really happening in the immediate environment of the roots. Measuring root-zone pH gives a better indication what is really happening locally near the roots. In short, recording pH closer to the roots will give a more representative indication of what is really happening near the roots. This will give new insights and improve watering and pH strategies to further improve growth.
The graph in figure 3 show a typical recording of pH in the root-zone. The pH is within the 5-6 range most of the time. On one instance (23rd) the pH drops below 5 which can be the reason for an adapted watering pH strategy because nutrient uptake can be comprised.