You will need:
- a handful of garden soil or forest floor soil
- a small stick
- a small glass jar
1. Half fill a glass jar with water and then put in a handful of soil.
2. Use the stick to stir the soil into the water. Then leave it to settle.
3. Watch as the soil settles in different layers. What falls to the bottom of the jar first? What settles above that? And what settles as the top layer?
Even if you wait a long time, the water will never become completely clear because some of the smallest pieces of clay will remain floating in it. Bits of plants and leaves will stay floating on the surface.
Try this experiment with soil from different places. Are the different layers in the jar always the same thickness?
Soil composition – What is soil?
Almost all the land on our planet is covered by a layer of soil.
Do you know what’s in the soil?
Soil is a mixture of living and non-living material.
It includes the rotting remains of plants and animals, tiny living things, air, water and small bits of rock.
Look at a sample of soil through a magnifying glass or under a microscope, and you’ll often see that it’s full of living things.
Some of these living things are small invertebrate animals, such as worms and insects.
Others are bacteria and molds—but you won’t see them.
These living things help to create a part of the soil that’s called humus.
Humus is the organic part of the soil, which means that it is made of material that was once alive.
Most of the humus is made from the leaves, stems, and flowers of dead plants.
The bacteria, molds, and invertebrates in the soil feed on this dead and decaying plant material.
The waste material which these organisms leave behind is full of nutrients that provide food for living plants to grow.
Humus also holds air and water in the soil.
The rest of the soil is made up of particles of rocks.
The big particles are sand and the smallest ones are clay. Because rocks are not living things, we say that they are inorganic.
Soil is a mixture of organic and inorganic materials.