What is soil made of?

Activity

Learn about the ingredients that turn into soil over a long period of time.

Learning objectives

Learn about the components of soil and how living things decompose
Learn that rocks and stones weather over time

Preparation

Make cards, pictures or examples (see below) of water, air, sand, clay, rocks and stones, dead and living plants and roots, worms and mini beasts, seeds, micro-organisms, animal faeces and dead animals.

Equipment

Small pots containing stones, gravel, pebbles, sand, clay, leaves and other plant material, pretend worms (wool), pretend insects such as beetles and woodlice, watering can to represent water, blown up balloon to represent air, and beads or buttons for soil microbes/ bacteria
Bucket
Pots
Cards or pictures
Stick to stir

Step by step

Introduce the concept that soils are like a cake; made up of different ingredients that have to be mixed together and then ‘baked’, or allowed to decompose or weather over a long period of time.
Ask your group to list the ingredients of soil, one at a time. Each time they name a correct ingredient, reveal that pot and add it to the bucket. Whoever names the ingredient is passed the bucket and stirs it. This continues until all the ingredients in the pots have been used.
Examine the contents of the bucket together and ask the pupils ‘Why doesn’t it look like soil yet?’.
The hidden ingredient is time, which involves decomposition and the effects of weathering (exposure to temperature changes and the chemicals in the rain) which in turn leads to soil formation.

Hints & tips

Soil has more creatures in it if organic matter (such as garden compost) has been added regularly.
There are far more ‘good’ bacteria in soil that help to keep our plants healthy, than ‘bad’ bacteria that cause diseases.