GROW Observatory
Jul 19 · 4 min read

Would you like to know how to measure and compare soil pH? Alice and Renee from the GROW Observatory team showed participants how to do these two related activities at the Permaculture Scotland Gathering in Scotland. Here’s their story.

GROW Observatory went to the Permaculture Scotland Gathering at Rubha Phoil, Isle of Skye on June 29. The gathering was themed Growing the Future: Practical Responses to Climate Change. There were talks, walks, workshops, and practicals with different individuals and organisations, including Extinction Rebellion, Fridays for Future, Monica Wilde, David Somervelle of Transition Edinburgh, and Stephanie Gooding of Earthworks to name a few.

Led by Alice Ambler, we ran a soil experiment workshop to help participants get to know the type of soil they have as well as measure and compare soil pH. Both of these can easily be done at home.

The Touch Test

The first soil experiment is called the touch test. This experiment is quite simple. First, get a handful of soil and add a little bit of water. Knead the soil with your hands. You will know that the soil has the correct consistency if it has the same consistency as a putty. If the soil is too dry, add more water. If it is too wet, add more soil. Form the soil into a ball and squeeze. Does it fall apart? If yes, the soil is sand.

If the soil doesn’t fall apart, the next step is the ribbon test. Squeeze the ball between your thumb and forefinger to form a ribbon until it breaks from its own weight.

Based on how long the ribbon is before it breaks, you can know what type of soil you have, from Clay (long, over 50 mm) to loamy sand (short, less than 10 cm).

While the ribbon test is not a method used by the Food and Agriculture Organisation (FAO), we did the ribbon test to see what classification we can get on the soil texture triangle:

You can compare the results of the touch test versus the ribbon test. With more participants, you can also compare each others’ results.

Here is a diagram of the experiment which you can print at home:

The next experiment we did was to test the pH of the soil using pH test kits which you can easily find online. A soil’s pH is important as it determines what types of plants can grow in it. Most crops grow well in soils with pH 6 (slightly acid) to 7.5 (slightly alkaline). Acid-loving plants with soil pH of 4.5 to 5.5 include blueberry, cranberry, and currant. Meanwhile, asparagus and garlic can grow in soils with a pH of up to 8.0.

To do a pH test, place a spoonful of soil in the test kit and add water. Shake it and let it settle. Once the soil settles, you will see the colour change based on the pH scale.

In the photo above, you can see that the colour is dark yellow, which indicates a pH 6.5 or slight acid as indicated on the scale on the right.

We then compared the readings from these low-cost kits with a professional pH meter and found that while the low-cost kits have similar readings to the professional pH meter, they are inconsistent and cannot replace a professional PH meter. A word of warning: in more detailed studies, we have found that this soil testing kit is unreliable for measuring a soil pH. However, these studies of ours also found that they could still serve to provide a rough guide between slightly alkaline/ neutral (pH: 7.5–7.0), slightly/medium acid (6.5–4.5) soil conditions.

Our participants enjoyed doing the experiment and said they will do a similar test in their gardens once they get home. One of our online viewers during our Instagram live also said that through the experiment, he learned what type of soil is best for him to grow his vegetables.

The kind of soil you have and its acidity or alkalinity determines how successful you will be in growing your vegetables or fruits. Doing these simple tests will improve the way you manage your soils and grow your food. Let us know if you’ve done it and what your results are! Tweet us or tag us on Instagram at @growobservatory.

For a more detailed account of how to do a soil type test, see here:

GROW Observatory Stories

GROW Food. GROW Soil. GROW Science.

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GROW Observatory Stories

GROW Food. GROW Soil. GROW Science.

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