What is soil made of?

Learning objectives:

Soil | Sand | Clay | Minerals | Organic | Humus | Particles | Texture

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

1. 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
   

   Decompose means to break down or decay into simpler substances. In gardening, it often refers to the process of organic matter breaking down when added to compost or soil. This process is important for creating healthy soil and providing nutrients for plants.

   or weather over a long period of time
2. 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
3. Examine the contents of the bucket together and ask the pupils ‘Why doesn’t it look like soil yet?’
4. 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

• Soil has more creatures in it if organic matter (such as garden compost
  

  Can refer to either home-made garden compost or seed/potting compost: Garden compost is a soil improver made from decomposed plant waste, usually in a compost bin or heap. It is added to soil to improve its fertility, structure and water-holding capacity. Seed or potting composts are used for growing seedlings or plants in containers - a wide range of commercially produced peat-free composts are available, made from a mix of various ingredients, such as loam, composted bark, coir and sand, although you can mix your own.

  ) 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