How to correct soil pH

The potential of hydrogen (pH) is a measure of the acidity or alkalinity of a solution. It is very important to take it into account when growing plants since there are some that grow better in acidic soils, called acidophilic plants, and others that develop better in alkaline ones.

For this reason, we are going to tell you how to correct the pH of the soil so that, in this way, your precious plants can develop without problems.


  • 1 Measure the pH of your garden
  • 2 How to lower the pH of the soil?
  • 3 How to raise the pH of the soil?

Measure the pH of your garden

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First of all, the first thing to do is to know what pH the soil has where you want to have the plants. It can be done at home, spending very little money, since you will only need:

  • Distilled water
  • Shovel
  • plastic container
  • pH strips (they are sold in pharmacies, hardware stores, hypermarkets, or in online stores).

You will see that the strips have several colors to which a number corresponds: from 1 to 14, with 7 being the one corresponding to neutral pH.

Once you have everything, it’s time to analyze the land :

  1. Divide your garden into squares of 1 or 2m2.
  2. Collect samples each square to a minimum depth of 45cm. If you plan to grow trees, you will have to go deeper: between 60 and 80cm.
  3. Now, mix all the samples homogeneously.
  4. Then, mix equal parts soil and water.
  5. Stir until a paste forms, and let it rest for a couple of hours.
  6. Finally, insert the pH strip and see what color it takes.

How to lower the pH of the soil?

blond peat

Blonde peat, substrate that acidifies the earth.
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If the pH of your soil is too high, that is, if it has a number of 7 or higher, you might want to lower it a little, right? To do this, I recommend that you mix the soil with blonde peat , which has an acidic pH. Spread a layer of 4-5cm all over, and do a pH test again after 5-6 months.

In case you don’t want to wait that long you can add aluminum sulfate to the soil as it lowers the pH as soon as it dissolves. The amount you should use varies depending on the pH of the soil, but in general terms, 0.5kg of aluminum sulfate is enough to lower a point on the pH scale in a 1m square patch of soil.

How to raise the pH of the soil?

Potassium carbonate, perfect for raising the pH.  Image -

Potassium carbonate, perfect for raising the pH.
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If the pH of your soil is too low, that is, if it has a number of 5 or lower, you will have to raise it if you want to grow plants that do not like acidic soils, such as carob or almond trees. To do this, the fastest and most effective way is using potassium carbonate that you will find for sale in herbalists or pharmacies. It is very soluble, so it can be applied by drip irrigation.

The only drawback is that you have to keep the pH below 7 to avoid clogging the emitter, but otherwise you only need to add a small amount  (a teaspoon is usually enough) to the water to raise the pH.

azalea in bloom

We hope that these tips will help you to correct the pH of the soil in your garden

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