This session was all about soil. We went to the field to collect soil samples to send to Hill Laboratories. We are going to order a basic soil profile and this will measure soil nutrient levels and indicate the existence of any deficiency, excess or imbalance of major nutrients. In order for the test results to be true, we had to collect 20 samples in a zig zag accross the field. It was a beautiful winters day and the kids loved being outside digging for samples and finding worms!
We then came in and worked on 2 different experiments to try to figure out as much about the school field soil as we could ourselves.
Jam Jar Experiment - Soil density column
Soil is made up of a mixture of sand, silt, clay and rotted plant (organic) material. Different soil types have differing percentages of each. The jam jar experiment shows what the proportions of these are.
We tried this experiment with soils from a woodland, garden and of course the school field! The soil needs to sit in the water for a few days to seperate so we will analyise the results in the next session.
We boiled up red cabbage and used the cabbage juice as an indicator of pH.
The recipe: roughly chop half a red cabbage and cover with water in a deep sauce pan, cover with distilled water (or filtered rain water) and boil until water takes on a deep purple colour, drain and retain cabbage juice for chemistry experiments. Eat or discard cooked cabbage leaves.
An indicator is typically a chemical that changes color if it comes in contact with an acid or a base. As you can see, the purple cabbage juice turns pink/red when it mixes with something acidic and turns green/blue when it mixes with something basic. Below Sarah adds baking soda to make a basic solution and vinegar to make an acid solution. You can make your own pH paper strips from blotting paper soaked in red cabbage juice and let them dry fully before dipping in fluids to be tested.
Why is red cabbage a good indicator of PH? Red cabbage contains an indicator pigment molecule called flavin, which is one type of molecule called an anthocyanin. This water-soluble pigment is also found in apple skin, red onion skin, plums, poppies, blueberries, cornflowers, and grapes. Very acidic solutions will turn anthocyanin a red color.
Testing soil pH using red cabbage juice
Boiling red cabbage in distilled water produces a hot juice which helps to dissolve the soil. It's very accurate if you let 1 large tablespoon of soil SOAK for at least 1/2 hour. Prolonged soaking releases soil elements to yield the most accurate result. You can test many samples of soil from your garden at the same time. we tested many samples and found that our soil on the field is neutral.