a scale used to measure the acidity or alkalinity of a solution. It goes from 0 to 14, where 7 is neutral. A pH value of less than 7 indicates acidity (acid), while a pH value of over 7 indicates alkalinity (base). The pH of the water used for irrigation is important for the plant to thrive. You therefore need to be able to measure and adjust the pH. This can be measured with a pH kit with indicator liquid or with an electronic pH meter. The pH value can then be adjusted to the optimal level using pH-op and pH-ned (available as both powder and liquid).