Soil acidity and plant preferences
Red cabbage contains a pigment (anthocyanin) that changes colour when mixed with acid or alkaline, which is measured as pH. Plants are adapted to different conditions, including soil pH. You can use red cabbage water to test the pH of soil and compare with the types of plant that grow in it.
You will need:
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Red cabbage
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Water
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A bottle
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Small containers (recycled jars are great, especially if they’re different as you can use this to identify your samples)
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Labels for your containers (if the container aren’t different and identifiable)
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A teaspoon
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Somewhere to collect soil samples
METHOD
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Chop up red cabbage and add about twice as much boiling water (adult!).
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When cooled, strain the water and put the water in a bottle to take out with you to test.
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Collect about 2 teaspoons of soil in each container.
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For each sample, mark the container and record the location (you can use grid reference, the What3Words reference or draw a map).
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Record which plants are growing in each sample location. You can record them straight away and/or revisit your sample locations and see which plants are growing at different times of year.
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Add enough cabbage water to each sample to cover the soil plus enough water above the soil to see the colour of the water.
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After about 20 minutes, check the colour against the chart to see the soil pH (it may be easier to pour a bit of water out onto a light surface, like the container lid)
