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What is pH, how is it modified, and why is it relevant?

A pH measuring device.

Water can be either neutral, acidic or basic.

The pH scale is the measurement of how acidic or basic water is, ranging from 0 to 14. 7 is neutral—neither acidic nor basic. A number lower than 7 is acidic. A number higher than 7 is basic.

The pH of water changes when acidic or basic substances are added to it. For example, adding minerals changes the pH of water because minerals have acidic and basic properties. Some substances are more acidic or basic than others and will have a greater influence on the pH of your water than others.

Accurate measurement of pH is important because the pH of water affects a plant’s ability to absorb minerals efficiently. When pH is out of range in the irrigation water a plant can even become blocked from absorbing nutrients that they need to survive.

pH also has an effect on the solubility of minerals. Minerals are soluble when water has a pH of 5.6-6.4. If pH drifts out of this range, minerals can precipitate out of solution. For example, calcium, iron and phosphate start to leave solution when pH rises above 6.5.

The pH of a feeding solution for cannabis plants should be kept between 5.8-6.3. This range optimizes mineral solubility and uptake.

The pH of water is measured using an electronic pH meter. pH meters must be calibrated before use using calibration solutions.

Growers adjust the pH of their solutions with commercially available pH Up and pH Down solutions. pH Up is a concentrated base that raises pH. pH Down is a concentrated acid that lowers pH.

pH up and down solutions are very concentrated and are best administered to water with a syringe or dropper.

pH needs to be monitored regularly throughout the entire growing process and adjusted to keep it within recommended range.