pH in a Nutrient Solution
The pH of a nutrient solution determines the availability and absorption of nutrients by each species of plant.
With this in mind, pH must be checked during the start-up of the new crop and then monitored at frequent intervals up until harvest. pH is measured on a scale of 1-14 with 7 being neutral. Acids are lower than 7 and alkalis are above 7.
Every plant species has a preferred pH range in which it will grow best. When the pH is not at the proper level the plant will lose its ability to absorb some of the essential elements required for healthy growth. For all plants there is a particular pH level that will produce optimum results (see chart 1 below). This pH level will vary from plant to plant, but in general most plants prefer a slightly acidic growing environment (between 6.0-6.2), although most plants can still survive in an environment with a pH of between 5.0 and 7.5.
When pH rises above 6.5 some of the nutrients and micro-nutrients begin to precipitate out of the solution and can stick to the walls of the reservoir and growing system. For example: Iron will be about half precipitated at the pH level of 7.3 and at about 8.0 there is virtually no iron left in the solution at all. In order for your plants to use the nutrients they must be dissolved in the solution. Once the nutrients have precipitated out of the solution your plants can no longer absorb them and will suffer (or die). Some nutrients will also precipitate out of the solution when the pH drops.
Commercially available nutrient solutions are balanced in pH, but when they are diluted with water from a different source i.e. tap water, the pH may change from acceptable to unacceptable for the plant.
pH in a Rockwool Slab Drip Feed System
pH in a Soil System
pH Test Kit
pH UP - DOWN
pH Buffer 4 and 7