pH stands for “Potential of Hydrogen” and is the symbol for the hydrogen ion (H+) in liquids. pH has a range from 0 (acidic) -14 (alkaline), with 7 being neutral. For hydroponics we are aiming for a pH between 5.5 to 6.2 (slightly acidic); this is suitable for most hydroponic crops. For soil, we want the pH a little higher but still slightly acidic; around 6.0 to 6.5. Ensuring that the pH remains within this range will help maintain good plant health. Keeping the pH in this range ensures that nutrients are readily available to the plant. Once the grower goes above or below this optimal range certain nutrients start becoming unavailable to the plant (e.g. iron deficiencies will appear at a pH of 6.5 and above).
All hydroponic growers need to test the pH of their nutrient solution for successful growing. The pH of a solution can be tested using a standard pH test kit (sample vial with drops of indicator solution), litmus test strips, or a digital pH meter. Litmus paper and standard test kits are cheap and easy to use; however, the degree of accuracy isn’t very high. Digital pH meters, although more expensive than the alternatives, are easy to use and very accurate.