Measure soil pH

Soil pH is a very important element What you need to know before you garden: indeed, this has considerable implications for crops, as it influences the ability of plants to absorb nutrients.

The pH score is not an abstract number: it is closely linked to the presence of calcium which is the most important of the microelements that vegetables need to grow strong and healthy in our garden.

Each plant has a “preferred” pH value, which corresponds to the ideal condition for healthy life and development. Most vegetables require a neutral substrate, between 6 and 7 while berries are generally acid-loving plants, which prefer lower pH values, around 4.5/5.

Soil tests are carried out in the laboratory, in the allotment garden, often the costs of a chemical test cannot be paid. However, we can learn to study the characteristics of our soil at home, and even do our own soil analysis.


The measurement of the pH of the aqueous extract of a soil is fortunately very easy to do “do it yourself”, using litmus paper available at any pharmacy, otherwise there are counters. Let’s find out how to measure the pH and above all what it means to have an acid or basic soil and what corrections can be made in organic farming.

Contents [Ocultar]

  • What is the pH value

  • ?

  • How to measure pH with litmus paper

    • How to take a representative soil sample

    • Use litmus paper

  • pH meters

  • How should the pH of the garden be

  • Correct soil pH

    • Correct acid soil

    • Correct a base floor

  • The pH of water


What is the pH value

The pH of a soil is the numerical measure of acidity, i.e. the concentration hydrogen ions (H+) in the “liquid phase” of the soil i.e. the circulating solution.

The acidity of a soil is determined by the relationship between hydrogen ions and hydroxyl ions the chemical compounds dissolved in the soil water contribute to the variation of this value.

I’ll leave out the big words, because I’m not very good at chemistry myself. The thing to know about who cultivates the garden is that pH has an important influence on a whole series of reactions that occur in nature and is decisive for the life of soil microorganisms. It also has effects on the activity of the root system of plants and in particular on its ability to absorb nutrients.

The theoretical pH measurement ranges from zero to 14, where the lower the value, the more acidic the soil. Around 7 we have a neutral soil while above we have basic or alkaline soils.

  • Soil acidity: pH less than 7 (the lower the pH, the more acidic the soil).
  • neutral environment : pH = 7.
  • Basic or alkaline soil : pH greater than 7 (the higher the pH, the more basic the soil).

How to measure pH with litmus paper

To measure the pH of the soil itself, there are basically 3:

  • Take a medium soil sample.

  • Put the soil in distilled water.

  • Use litmus paper.

These are very simple things, but you have to do them carefully so as not to affect the measurement. In particular, the collection of the sample must be explained.

How to take a representative soil sample

First, if you want to measure pH correctly, you need a soil sample that correctly represents your orchard.

Soil is not homogeneous, so if we want to get an average sample, we have to take the soil from several places (sub-samples) and then mix . We then take 5 or 6 sub-samples from different places in the garden.

You shouldn’t take very deep soil, but you shouldn’t take very shallow soil either. Each subsample must be taken at a depth of about 10 centimeters .

If fertilization has just been carried out, it makes no sense to measure the pH, because the reactions caused by the added organic matter change the values.

Use of litmus paper

After taking the different samples, mix them with to get the average sample .

A tablespoon of soil from this sample should be placed in a glass of distilled water which is stirred while stirring.

For a more accurate measurement, keep the ratio of 10 grams of soil for 25 ml of water . It is important that the water is distilled because otherwise the composition of the water alters the measurement.

litmus paper it is immersed in a solution of water and earth, the immersion time is specified on the packaging.

depending on the color from the card, the pH measurement is obtained.

Litmus paper is easy to find and cheap, on the web you can find it in bulk for a few euros.

pH meters

There is also digital pH meters easily available for sale on the web, are also called piacameras or phmeters.

I personally think that it is not worth investing in an expensive and expensive counter.

There are also cheap electronic meters, but beware: a phm meter that is too cheap may not be reliable. For this reason, I suggest to those who want to analyze garden soil lean towards the litmus paper .

What should the pH of the orchard be?


Once you have learned how to measure, it is good to learn how to evaluate the results obtained and to know when a soil is considered acidic and when it is acidic (or alkaline).

The soil is neutral with a pH of 7, the highest values ​​are those of alkaline soils, below 6 you have soils with a tendency to acidity. If the measurement indicates a soil between 6 and 7 will be excellent for most vegetables . When the pH is below six, it needs to be made more alkaline, you can try to correct it with a calcium supplement.

PH and plant life

pH interferes with cultures and for this reason it is useful to measure it even for a simple orchard .

Without going too far into the specific chemical and physical implications of acidity, we can say that the main effect for plants is promote or not the absorption of certain microelements . An acidic environment promotes the absorption of elements such as iron, copper, and zinc, while others, such as calcium and magnesium, are readily absorbed in alkaline environments.

Each plant has a different nutrient requirement, so it can do better in acidic or neutral soils, and more rarely in basic soils. Most vegetables prefer soil between 5.5 and 7 (i.e. neutral or slightly acidic). fruit trees are also found on average in the same values.

Some plants prefer lower values, for example apple trees (ideal pH between 5 and 6) and potatoes (pH between 4.5 and 6).

Berries are acid-loving shrubs and grow well where the soil has pH values ​​below 6. Other acid-loving plants are citrus.

correct soil pH

After measuring the soil and detecting the pH value, we can decide whether it is suitable for cultivation or whether it needs to be corrected. pH correction possible although when a soil is too acidic or basic, it is best left alone.

If a piece of land has a certain vocation, it is also likely to reappear over time, so remediation is not just a one-time job, so it requires constant vigilance with possible maintenance interventions.

Correct acid soil

If you have acidic soil, you have to correct it by making it more basic. This can be important to allow the plant to assimilate certain elements, in particular calcium, responsible for the apical rot of tomatoes for example.

For each pH point to recover, we can add hydrated lime at a dose of 400 grams per square meter of orchard. This operation is authorized in organic farming, it must not be carried out in the presence of organic matter (compost or manure) but on clean soil. you can also use calcium carbonate .

It is best to proceed step by step and slowly correct the pH, varying by half a point and repeating the operation after a few months.

The most artisanal methods of correction involve the use of wood ash or calcareous algae flour (lithotamnium).

Correction of a base floor

If the pH is above 7, the soil is alkaline or basic, it must be corrected. You can do this by mixing blonde mob to make it sour or by using sulfur . Peat is not an environmentally friendly material, let’s take this into account when choosing it.

This too must be done gradually and requires constant monitoring for years to come. To maintain acidic soil after correction, you may choose to provide compost or organic mulch which tends to be acidic.

water pH

In some cases, it may also be useful to measure the pH of the water.

Irrigation water can be basic or acidic, this can vary in soil pH over the long term, but if soil pH is controlled, water measurement can be omitted.

However, when treatments with insecticides or fungicides are carried out, it can be very important check the pH of the water used to dilute the substance a, because some active ingredients can be inhibited in water that is too acidic or too basic.

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