Measuring the pH of the soil is an operation that, with due care, is within everyone’s reach. We have already discussed the meaning of the soil’s chemical reaction (pH) and its implications for agricultural cultivation. In this article, we want to focus our attention on the homemade measurement of this important value. Usually, this operation is entrusted to analysis laboratories, a recommended choice for large plots of land and significant investments.
In the home garden, on small plots, pH measurement can be done independently. This can save us significant expenses.
Let’s see how to measure soil pH and what we need.
Measuring Soil pH with Litmus Paper
The simplest method for measuring soil pH is to use litmus paper (or colorimetric paper). Not everyone knows that litmus is a dye of plant origin, extracted from lichens. This dye is used in chemistry on special supports, namely strips of paper called “litmus papers.” The papers change color depending on the pH of the environment in which they are placed. This characteristic makes them an excellent indicator to determine the soil’s chemical reaction.
The paper color will be green with a neutral pH, more or less red in an acidic environment, and blue in a basic environment. It won’t give us a precise measurement, but it will still provide a reliable reference to assess the soil’s acidity or alkalinity. Therefore, such a tool is an effective pH meter. If you are interested, you can purchase it with ease here.
Soil pH Measurement Procedure
What You Need
To measure soil pH, in addition to litmus paper, we need:
How It Works
The soil pH is detected in the aqueous suspension of the soil sample and distilled water with a weight/volume ratio of 1:2.5. To better understand, every 100 g of soil requires 250 ml of distilled water to prepare the aqueous suspension.
It is essential to respect these proportions, which are a standard in the scientific community, as the pH is lower, the lower the soil/water ratio.
How to Proceed
To get an accurate indication of the soil pH measurement, you need to choose the right sample for analysis. Firstly, avoid taking soil from areas that have been recently fertilized, for example, with wood ash, compost, or earthworm humus. Taking soil from these areas with fresh fertilizer alters the result. Identify a resting area, preferably in the center of your agricultural land. With a shovel, dig a deep hole and take the soil sample at about 20-25 cm deep. At this point, refine the soil through a sieve or an old colander. Once the soil is refined, take the amount you need and put it in the glass container. Now add distilled water and start stirring. Take some time in this phase and stir regularly for at least 15 minutes. Let the sample rest, closing the glass jar and waiting for the soil to settle at the bottom. It is good, at this point, to let at least another 30 minutes pass. At the end of the process, we are ready for the measurement, which involves immersing the litmus paper in the aqueous suspension. Immersion times and test results must follow the paper’s instructions. For a more precise and reliable result, we recommend taking multiple measurements at different points in the soil.
Soil pH Measurement by Potentiometric Method
In analysis laboratories, measuring soil pH follows a similar but less empirical and more standardized process. The most reliable measurement is potentiometric, which occurs using pH meters. These are instruments equipped with electrodes with a glass membrane, measuring the electric charge of soil acidic and alkaline ions.