Understanding Soil pH
The soil pH level may not seem like an overtly important factor to consider, but surprisingly enough it is. Although cannabis is generally regarded as a very hardy plant, you’ll want to maintain a healthy, neutral pH in order to avoid stunting or killing your plants. Luckily, maintaining a good pH isn’t too hard to do, especially if you monitor your grow closely.
As you may remember from your high school science classes, pH refers to how acidic or how basic something is. On a scale measured from 0 – 14, a neutral pH is considered to be 6.5 – 7.5; to give you an idea, lemons and limes are rated at about a pH level of 3. Stomach acid, a much more acidic compound, is rated with a pH of 1.
On the more basic end of the spectrum, glass cleaners and dish detergents have a pH of roughly 10, oven cleaners are even more basic with a pH of 12, while lye and liquid plumber have a pH of 14. Back in the more neutral zone, both blood and distilled water have a pH of about 7.
The reason pH is so important for your cannabis grow is because your plants can’t make use of their nutrients when the soil is too acidic or too basic. When the soil becomes too basic, the roots of your cannabis can’t absorb the nutrients; and when the soil is too acidic, the nutrients form acidic salts, rendering them totally unavailable for your cannabis plants.
Ideally, your soil and water / nutrient blend should be balanced at a pH of 6.5 -7. You can test the pH of your soil or water with paper test strips that are widely available, or you can invest $20 – $30 in an electronic pH testing device, they are commonly available from garden supply stores.
If you use an electronic pH tester, be certain to water your soil with pH neutral (distilled) water before testing the pH. Electronic pH devices are designed to be used in moist soil, so if your dirt it too dry, you won’t get an accurate reading.
Always be sure to check the pH of your soil and water if your plants start showing signs of stress; many growers immediately assume there are nutrient problems, but you may have an underlying pH problem. Some growers also have issues with hot spots or pockets of concentrated nutrients, particularly if they’ve mixed their own soil blend. To avoid hot spots in your soil blend, be sure to mix your soil very thoroughly and break up any clumps before planting.
A great way to ensure that your soil maintains a healthy, neutral pH is to add dolomite lime to your soil. Dolomite lime is a calcium-magnesium carbonate that naturally maintains a neutral pH of 7, so you can mix 1 cup of dolomite lime per cubic foot of soil. Managed properly, with dolomite lime you can keep your soil at a nice neutral pH for the entire growth cycle.