When it comes to learning about hydroponics and aquaponics, it’s likely that you’ll run into a few unfamiliar terms. In particular, there’s a lot of mumbo-jumbo about pH—we know it’s important and we know that it affects the way our plants grow in the system. But what exactly does that mean; why does it have such a big impact on the success of our farms? Let’s dig into the chemistry a bit.
pH is a measure of acidity, which matters because nutrients are more or less available at different levels of acidity. That means you’ll need to find the sweet spot on the pH scale where all of the nutrients are available, and the plants are getting what they need.
pH is represented by a scale that ranges from 0 to 14 (0 being the most acidic and 14 being the most basic). The term “pH” stands for “potential hydrogen” because hydrogen ions (H+) and hydroxide ions (OH-) are what cause a solution to be basic or acidic. pH tests measure the concentration of these two substances in a solution. Because there are so many, measuring a number of hydroxide or hydrogen ions is not practical, so instead, pH is measured on a logarithmic scale (we’ll get to that shortly).
This is where things get more complicated. As you know, water is made up of hydrogen and oxygen. Two hydrogens, in fact. Pure water has a pH of 7, which means that it has an equal number of hydrogen and hydroxide ions because nothing else is in the water to break up the atoms.
As water molecules break up, (which happens when a nutrient mix reacts with water), the water becomes acidic or basic. Another way of saying this is that water molecules are broken down and hydrogen and hydroxide ions are formed. pH depends on which is formed in higher concentration. We measure the concentration of hydrogen in relation to hydroxide; the critical measure is the hydrogen ion concentration.