Gardening Basics

How to determine pH levels in soil

October 14, 2011

The pH meter

The nature of the soil plays an important role in determining the nature of a garden! Everyone will know this intuitively. But what everyone will not know so naturally, is the fact that there are elements beyond moisture and nutrients that determine the nature of the soil. We shall examine one such element called the pH. pH is actually a measure of the hydrogen ion or proton concentration in a place. If you do not understand these terms don’t worry. Just know that pH is a measure of how acidic a thing is. The soil in the garden can either have an acidic nature or a basic/alkaline nature. If it is exactly balanced, then it is known to have a neutral nature. It is virtually impossible to have perfectly neutral soil in natural conditions.

Why to test pH levels?

Soil is always either acidic or alkaline. There are plants that thrive in acidic soils while there are others who prefer alkaline soil. Most of the plants however need neutral or almost neutral soil. Testing the pH levels of the soil helps one to take decisions on plant choices. If the plant choice has already been made, then the pH testing will help decide the necessary course of action (to alter the nature of the soil) to suit the selected plants.

Steps included

1. The first step would be to gather the necessary materials. These include a pH tester, clean wipes or tissues, a small spade or a trowel, distilled water, a paper cup and a cloth piece.

2. Once you have gathered all the materials, select a spot in the garden where you would like to test the pH.

3. Dig a small hole in the soil, at the spot, using either the trowel or spade. The holes should be about 2-4 inches deep.

4. Clean the hole of all the debris. There will be some roots sticking out. A few twigs and sticks buried may also be present. Clear all the debris. Pull them out if necessary.

5. Fill this hole with distilled water. Pour in the water till about 1/4ths level of the hole is filled with water.

6. Wipe the end of the tester with a clean and dry tissue.

7. Calibrate the tester by placing the testing rod in a cup of the distilled water. Distilled water has a pH of 7.

8. Wipe the testing rod with another clean tissue.

9. Place the testing rod in the water of the hole that has just been dug. Insert the probe into the mud.

10. Keep the probe (testing rod) in the soil for about 60 seconds.

11. Take a look at the meter and record the pH reading that is displayed there.

12. Note that a pH level of below 7 indicates that your soil is acidic. It it is about 7, then your soil is neutral. If the pH readings are above 7 (up to 14) then the soil is acidic.

13. Test the pH level of the soil in the same way at different places and spots in the garden. Take the different readings and calculate the average pH of the soil before you decide the appropriate treatment.

Quick Tips

1. When you are filling the hole with distilled water, you will have to pour more than the capacity of the hole for the soil will absorb quite a bit of the water.

2. It would be ideal if the pH meter is digital for the accurate values can be obtained.

3. If the pH reading at one particular spot is varying greatly from the others, know that this is an ‘outlier’. This means that this value should not be included in calculating the average pH of the soil. This spot should receive unique and separate treatment.

4. There are also a couple of quick tests. Pour a little vinegar on the soil. If it fizzes, then it is alkaline. If the fizzing comes when you sprinkle baking soda over wet soil, then the soil is acidic.

Things to watch out for

1. It is very important that the water being filled into the hole be distilled. Distilled water is commercially available. Distilled water is pure water without even traces of salts or other materials. Rainwater is already acidic and so will alter the values of the project. Bottled drinking water is also not of neutral pH.

2. It is important that the probe be inserted into the mud properly.

3. If the pH meter is an analog meter, it is important to avoid the parallax error while taking readings. To get the exact reading, close one eye and align the open eye, straight, in line with the needle of the meter. The readings seen this way alone will be the perfect values.

4. Note that the quick tests do not show how acidic or alkaline the soil is.

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