In the Anthurium and Phalaenopsis cultivation, a lot of attention is paid to acidity. The acidity, or pH value, is a logarithmic scale indicating the number of H+ ions. Water with a neutral pH of 7 has as many H+ ions as OH- ions. A pH below 7 is acidic and a pH above 7 is basic (alkaline). The scale is logarithmic, which means that a pH of 6 is ten times more acidic than a pH of 7. The pH value is important for the absorption of several nutritional elements. At a high or low pH, certain nutrients cannot be absorbed properly. For both Anthurium and Phalaenopsis, the optimal pH is between 5 and 6. At a high pH, substances such as boron, phosphates and copper are difficult to absorb. At a low pH, nitrogen, molybdenum and sulphur are difficult to absorb. At an extremely low pH, symptoms of poisoning can also occur due to manganese or aluminium, for example.
When rain or osmosis water is used, there are very few dissolved substances in the water.
To dissolve the fertilizers in the tank, it is important that the pH does not exceed 6.
Acidity of the substrate
The pH of the substrate is often different from that of the irrigation or drain water. This is caused by two processes.
Influence of soil organisms
Ammonium-containing fertilizers are converted to nitrate by soil organisms. This process is called nitrification.