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A easy way to test soil alkalinity or acidity

From a soil science course with Lancaster University, here is an easy and inexpensive way to test the acidity or alkalinity of soil. Useful if one does not have access to a soil test kit or laboratory testing. It won’t give numerical results but it will indicate if the soil is acidic, alkaline or neutral.

You will need – a pot of boiling water, a red cabbage – it must be a red cabbage, vinegar and baking soda.

Finely chop the cabbage.
Bring to the boil a pot of water. While distilled water is recommended, tap or bottled water will do if distilled is not available.
When boiling, add the chopped cabbage and remove from heat.
Leave to soak for 10 minutes.
Drain off and keep the purple liquid.

Put a small amount of purple cabbage juice into each of 3 cups.
To one cup add vinegar. The solution will turn pink indicating acidity.
To another cup add baking soda. The solution should turn blue or green indicating alkalinity.
To the last cup add two teaspoons of soil and stir through. Leave to soak for 15 minutes then check the solution.

A purple or violet soil sample indicates a pH near 7 (neutral).
If the sample turned pink the soil is acidic with a pH between 1 and 7. The brighter the pink the more acidic the sample.
If the sample turned blue or green the soil is alkaline with a pH between 8 and 14. The brighter the green the more alkaline the sample.

A fun experiment.

Posted over 1 year ago

Oops, please excuse the typo, that should be: AN easy way ,,,

Posted over 1 year ago


Folia Helper

United Kingdom8a

Sounds like a fun method of testing one’s soil!

Posted over 1 year ago

Yes, it does. I used my pH meter for the activity but plan on finding a red cabbage next time I’m doing the grocery shopping and comparing results out of curiosity – and to test the accuracy of my meter.

Another activity I found particularly fun, interesting and useful was testing one’s soil type. I followed the instructions with a teaspoon of soil from my garden and discovered that my soil is actually sandy clay. Until then I had thought it was just plain clay.

I tried attaching the file, but it wouldn’t connect, so here are the instructions:

Lancaster University | Practical activity – testing soil texture
Place approximately a teaspoon of soil in your hand. Break it up and remove any stones. Add a small amount of water to make it moist. The soil should feel like putty, not wet and sloppy, but not too dry to hold together.

Squeeze the soil into a ball. Does it stay in a ball? If it doesn’t, then you have sand.
Rub the ball with your thumbnail and note whether it shines.

Flatten the ball to form a ribbon about two millimetres thick. If the soil does not form a ribbon, you have a loamy sand. How long before the ribbon breaks? Note this down.

Get a small amount of soil really wet and rub it between your fingers. Does it feel gritty or smooth? If your ribbon is less than 5 centimetres long and you didn’t notice any shine, then there are three options. If it’s gritty, you have a sandy loam. If it’s smooth, you have silty loam. And if it’s a bit of both, then you have a loam.

If your ribbon extends to between 5 and 8 centimetres long and has a slight shine and it’s gritty, then it’s a sandy clay loam. If it’s smooth, it’s a silty clay loam. And if it’s a bit of both, it’s a clay loam.

If your ribbon reaches more than 8 centimetres and shines when rubbed, then it’s a type of clay. If it feels gritty, it’s a sandy clay. If it feels smooth, it’s a silty clay. And if it’s a bit of both, then it’s a clay.

One point to remember if trying any of these activities, and one that was drummed into us, is, after handling soil – wash your hands. You would be surprised at the number of organisms (estimated at 100,000,000,000 bacteria alone) living in a teaspoon of soil!

Posted over 1 year ago | Last edited over 1 year ago

I certainly will try this. Thanks, Carol.

Posted over 1 year ago

i cant find red cabbage here╭(°A°`)╮

Posted over 1 year ago
[This post has been removed by the poster.]

I haven’t found a red cabbage as yet, either. Probably the wrong season. I do see them in the supermarket from time to time, so just keep looking as the months pass.

Posted over 1 year ago

I saw a red cabbage in the supermarket the other day and immediately remembered the experiment. I bought the cabbage and decided to try the test.

It worked and returned the same result as my pH meter, moderately acidic soil.
I’ll try and upload the photos of the experiment here, but seem to only be able to load I file per comment. So here goes …

Photo 1 soaking the cabbage

Posted 12 months ago | Last edited 12 months ago

Photo 2 dispensing the liquid into 3 cups

Posted 12 months ago

Photo 3, adding the vinegar to one cup, bicarbonate soda to another cup.
(The third cup is reserved for adding a soil sample.)

Posted 12 months ago

Photo 4, a close up of the bicarbonate soda cup – the sample turns a green shade. (Harder to see in the photos.)

Posted 12 months ago

Photo 5, the test results after leaving the soil sample to sit overnight.
The soil sample turned a dark brownish pink, almost a purple but with definite pink undertones, indicating acidity rather than neutrality.

That result agrees with my pH meter.

Again, the resultant colours are harder to see in the photos than with the naked eye.

A fun test, and now I know that red cabbages are available mid autumn in the supermarkets.

Posted 12 months ago

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