Measuring the pH of the soil is an operation that, with due care, is within everyone's reach.
We have already told you about the meaning of the chemical reaction of the soil (pH) and its implications for agricultural crops.
In this article we want to focus our attention on the artisanal measurement of this important value. Usually this operation is entrusted to analysis laboratories, which is recommended in the case of large plots of land and therefore large investments.
In the home garden, however, on small plots of land, pH measurement can be done independently. This can avoid significant financial outlays. So let's see how to measure the pH of the soil and what we need.
Measuring Soil pH With Litmus Maps
The easiest method to measure the pH of the soil is to use litmus maps (or colorimetric maps). Not everyone knows that litmus paper is a colorant of vegetable origin, which is extracted from lichens. This colorant is used in chemistry on special media, i.e. strips of paper called "litmus paper". The maps change colour according to the pH of the environment in which they are placed. This characteristic makes them an excellent indicator for establishing the chemical reaction of the soil.
The color of the map will be green with neutral pH, more or less red in acidic environment, blue in basic environment. It will not give us an accurate measurement, but it will still provide a reliable reference to assess the acidity or alkalinity of the soil. So such an instrument is an effective pH meter. If you are interested you can easily buy it here
How It Works
The pH of the soil is measured on the water suspension of the soil and distilled water sample with a weight/volume ratio of 1:2.5. To understand better, every 100 g of soil requires 250 ml of distilled water to prepare the aqueous suspension.
It is very important to respect these proportions, which are a standard in the scientific community, as the pH is lower the lower the soil/water ratio. You can read more here https://bumpercroptimes.com/how-to-raise-ph-in-soil-with-baking-soda/.
How To Proceed
In order to have an accurate indication of the pH measurement of the soil, it is necessary to choose the right sample for analysis.
First of all, you should avoid taking the soil from areas that have been recently fertilised, e.g. with wood ash, compost or earthworm humus. Taking soil in these areas with fresh fertiliser will alter the result.
It is therefore necessary to find a resting area, preferably in the middle of the plot of agricultural land.
With a spade we dig a fairly deep hole and take the soil sample at a depth of about 20-25 cm.
At this point we end the soil through a sieve or an old colander. Once the soil has been refined, we take the quantity we need and put it in the glass container. Now we add the distilled water and start mixing.
We need to waste some time at this stage and stir regularly for at least 15 minutes. Then let the sample rest, closing the glass jar and waiting for the earth to settle on the bottom as mentioned here https://extension.umd.edu/hgic/topics/soil-testing.
It is good, at this point, to let at least another 30 minutes pass.
At the end of the procedure we are ready for the measurement, which is done by immersing the litmus paper in the aqueous suspension. Immersion times and test results must follow the instructions on the map.
For a more precise and reliable result we recommend taking several measurements at different points in the ground.
Measuring The pH Of The Soil By Potentiometric Means
In analysis laboratories, measuring the pH of the soil follows a similar but less empirical and more standardized procedure. The most reliable measurement is the potentiometric one, which takes place with the use of pH-meters. These instruments are equipped with glass membrane electrodes, which measure the electrical charge of the acid and alkaline ions in the soil.