How to Measure and Adjust pH in Soil


All plants, including cannabis plants, must be planted and grown in a soil containing a specific pH level. A soil pH value often determines whether or not a plant will be able to absorb the necessary nutrients present in the soil. The wrong pH level could result in a wilted or dying plant.

Remember the ideal pH for marijuana plants is between 5.5 and 6.5.

Measuring the pH Value

First things first: growers must first identify whether the pH value of the soil is at fault for a poorly growing plant. To do this, you will need to test the soil. Making adjustments to the soil without first testing it could simply cause further problems.

Fortunately, it is quite easy and affordable to test the pH levels of the soil. This can be done with hand-held pH meters which are referred to as pens. There are different types of pens, each using various types of electrodes. A common material for the electrodes for these pH meter pens is glass. There are also sturdier versions such as the ISFET pH meters. These utilize Ion Sensitive Field Effect Transistors instead. The pH meters can also be categorized as being either splash proof or waterproof.

How to Adjust pH Value in Soil Systems

By adjusting the pH value in soil systems, growers are either raising, lowering, or stabilizing the pH level in the soil. Here is how it can be done:

Stabilizing the pH Level

Certain plants respond to a neutral pH level, which means the soil needs to have a pH value of 7. The most effective way of stabilizing the soil is with the use of Dolomite lime. Dolomite lime has a pH value of 7. Therefore, when it is added to soil, it neutralizes the surrounding soil as well. If you trying to stabilize the soil before planting, you can mix fine Dolomite lime powder. To make adjustments once you have already planted, you should employ hydrated Dolomite lime powder instead. Typically, an ounce of Dolomite per gallon of soil is a good ratio.

In addition to neutralizing the soil’s pH level, Dolomite lime contributes calcium and magnesium to the soil as well.

Making the Soil More Alkaline

Dolomite lime can also be used to make a soil more alkaline if the tests show that it is overly acidic. Unlike when you are attempting to stabilize the soil, however, you will need to mix smaller amounts of Dolomite lime. Other options that you can add to the soil include hardwood ash, crushed marble, bone meal, or even crushed oyster shells.

Lowering the pH Level

There are several types of debris that can be utilized to lower the pH value of the soil. Composted leaves, cottonseed meal, wood chips, peat moss, leaf mold, and sawdust can all be added. With cannabis plants, there are a few other options. When the plants are in the vegetative state, growers can combine either blood meal or cottonseed meal to make the soil more acidic. When in the flowering stage, however, bone meal can be included in the soil.

This is how the pH level of the soil can be measured and then be altered.

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