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By: Tucker Eldridge

The pH scale measures the level of acidity and alkalinity in a given substance. This measurement is done on a scale of zero to fourteen, with anything above seven being alkaline, and anything less than seven being acidic. Pure water has a neutral pH of 7, and its pH shifts with the addition of salts that form a solution. When growing plants, the pH of our water, our nutrient solution, and our soil impact the availability of each nutrient our plants need to survive and thrive.

When checking our pH during the growing process, we want to make sure that we keep it within the acceptable range for the given media that we are using. In hydroponic media, this acceptable range is pH 5.8 to pH 6.2. While growing in soil our model range runs from pH 6.2 to pH 6.5. Keeping within these ranges does not make all nutrients the most available to the plant that they can be, but rather makes them available to the plant in the ideal ratios the plant needs for optimal growth. It is important to note that plants seem to flourish when fed at a range of pHs instead of at a very specific number; so if I am placing my nutrients into my reservoir, and they are drifting up over time, then I know that if I pH them to 5.8 they will
move up and through my acceptable range as opposed to adjusting to 6.2 and immediately having it move out of range.

pH is measured when growing using a pH probe. A pH probe is nothing more than a pH electrode attached to a voltmeter, which measures electrical charges in the solution, and converts them to a readable and consistent scale. These devices can be tedious to maintain, so always make sure that your pH probe stays submerged in pH neutral solution when not in use, that your meter does not submerge in water completely, and that you clean and calibrate your meter as frequently as possible. These steps will prolong the life of your meter substantially, while also keeping your measurements as accurate as possible throughout that life.

Once we have an idea of what our base pH is thanks to our meter, it is time to adjust it to within our acceptable range. Most commercial pH adjustors are either potassium hydroxide for pH up or phosphoric acid for pH down. This is important to be aware of because these two substances will contribute to the ppm’s of our solution. It is also important to be aware that if we add pH down to our solution and overshoot our desired pH, it is not in ANY way detrimental to our plants to adjust that same solution back up using pH up. Combining these two substances does nothing but create WATER, and potassium phosphate, which accounts for your ppm jump.

With a basic understanding of what pH is, how it is accurately measured, and how it is safely corrected, we can make sure our plants have everything they need at any given time to be as successful as possible.