Getting the pH of your nutrient solution correct is a very important part of hydroponics. Here is a guide to help you understand what you need to know.
pH is measured on a scale that measures acid to alkaline balance. 1 is the most acidic 7 is neutral and 14 is most alkaline.
Every point on the scale signifies a 10 ten-fold difference in acidity or alkalinity. For example, a pH of 5.0 is 10 times more acidic than a pH of 6.0 and a pH of 8.0 is 10 times more alkaline than a pH of 7.0.
Getting your nutrient solution correct is important because it affects how nutrients are made available to your plants.
If the result is too high or too low, some nutrients are “locked out” and this results in nutrient deficiencies which can affect plant growth.
How do I check the pH?
There are 2 ways to check the pH of your nutrient solution.
One method is by using pH strips. You simply dip the strip in water and compare the color of your test strips to the color chart provided. These test strips are inexpensive and easy to use but the down side is that you won’t get a precise measurement and of course there are a limited number of strips per package.
Another method is to use an pH meter. The down side is cost, but this option is more convenient and accurate. You will also be able to do an infinite amount of more tests.
How do I adjust the pH of my water?
In hydroponics we adjust the pH by using 1 of 2 solutions:
We raise it by using pH UP which usually consists of potassium hydroxide or sodium hydroxide.
We lower it by using pH DOWN which is made of phosphoric acid or sometimes food grade citric acid.
Just add the desired amount of solution to your water to reach the appropriate level for your crop and you’re done. Make sure to check the nutrient solution at least once every few days and make adjustments as needed.
For more information on how to prepare your water for hydroponics, check out the article water preparation for hydroponic nutrient solutions.
I’ve also included some charts below to help you find the correct pH of the different plants you can grow using hydroponics.