Practical observation: What's in soil?

Using soil samples from your own area, your class will get up close and see what they can find inside different soils.

A practical observation activity looking at soil in detail, with discussion points about soil contents and soil quality for plants and earthworms. 

• Key Stage: KS2 Year 3 (ages 7-8)
• Time required: Activity 20 minutes, discussion could last longer. (Set-up, digging up soil samples, 20 minutes)

Running the activity

1. Setup. Select two or more locations around your school grounds or in your local area (with permission!) where soil can be accessed and dug up temporarily. Give each of these locations a name such as ‘Flower bed’, ‘Roadside’ or ‘Edge of school field’ etc.        

Using a trowel, dig up a small sample of soil at each location and place it in a tray with that location labelled. Bring back to the classroom or take a picture of each sample. If you lack nearby natural soils to take from, purchased compost soil and sand can be good alternatives.

2. Discussion. Back in the classroom, begin by discussing what is meant by ‘soil’ and what you might expect to find in it. Consider both living and non-living things.

3. Observation. Look closely at the different soil samples. This can be done in groups with magnifying glasses or as a whole class if you have a whiteboard visualiser. Think about what you see.  

• What can you see in the soil? 
• Is there anything that animals such as earthworms would like to eat (organic matter such as leaves)?
• Which sample(s) would you expect to see lots of animals living in? Why might they be living here?
• Which ones would you not expect to see many earthworms in? Why would they not like to live here?
• Which sample(s) would you expect to see plants living in? Why? (The presence of earthworms makes soil better suited to plant life - see background science section below.)
• Do you think all soils are the same? Why/Why not?
• Do you have any evidence from looking at the samples to support this? (Differences observed in samples eg finer grains, wetter etc.) 
• If you looked at soil from a very different location such as a beach, riverbed, volcano or a rainforest, what differences might there be compared to the soil you looked at today?
• The soil you looked at today was from near the surface. How could you get a different sample from the same place? (Depth)

If conducted in groups, each group could report back their findings and attempt to answer the questions with any evidence they have considered.

Remember to return the soil to the exact places you removed it from.

Background science

Soil is made up of smaller pieces of rock and minerals as well as organic matter. Microscopic organisms, fungi and larger organisms (such as earthworms) play a part in breaking down organic matter which then appears in soil.  

If you opted for purchased soils, many compost mixes contain a mixture of organic and inorganic material. Most multipurpose composts contain purely organic material, packaged top soils are mostly inorganic and sand is entirely inorganic.

The sampling conducted in the activity requires observation of the physical make up of soil. The same process the scientists at the Museum will use to investigate soil.

Soil sampling is important for many of our Museum scientists in their research. The conditions of soil play a large part on the wider ecosystem as many organisms depend on healthy plant life to thrive and many plants rely on certain organisms in the soil.

Scientists at the museum take soil samples in different locations to see how it supports the wider ecosystem. Sometimes it can help show evidence of human actions that are reducing soil quality, such as: the leaching of nutrients, squashing the soil so water can’t get in, or the presence of human-made non-biodegradable waste. 

As well as promotion of a healthy ecosystem and related biodiversity, assessing the soil can be vital to agriculture - which humans depend upon for food. The museum has worked on projects such as EXCALIBER for such reasons.

In the United Kingdom, earthworms are considered beneficial to improve soil health. The presence of earthworms and their burrowing creates space for air and water to move through the soil. This will allow for plant growth as they benefit from space to grow and water moving through. 

Earthworms also bring down and consume organic matter such as leaf litter and their waste (‘worm castings’) provides nutrients in soil. 

The relative acidity/alkalinity of the soil is something scientists check when sampling. Some organisms, plants and animals, cannot live at certain levels of acidity/alkalinity. At lower KS2 it is not expected to be taught, but if so desired it can be tested with soil by putting some vinegar on a piece and seeing/listening if it fizzes. This only works if the sample has chalk present.

Suggested extension activities and differentiation

Useful words
Learners at year three level may benefit from a simple word bank of relevant terms and unusual plurals. Earthworm, Soil, Plant, Leaf/Leaves. The term ’organic’ (being made of parts of living or once living things) may need to explained to all learners. 

Soil Sorting
As a class, sort the soils in order of different factors. This works best with three or more samples. These could include: ‘best suited to plant life’ or ‘more likely to be found near or in water’.

Expect decisions made by students to be reasoned scientifically, eg: 'We found leaves in this sample so earthworms would have something to eat. If there are earthworms then plants will grow better from their tunnels and poo. That’s why we think this sample would be most likely to have plants in it.'

Summon the Worms!
You might like to try the Summon the worms! activity at the same locations of the soil samples to cross reference the results. 

If they do not match closely, consider other factors such as material harmful to earthworms going into the soil, recent movement of the soil or the presence of predators such as moles.

Leaf Litter Pick
Go on a ‘leaf litter pick’ to help your local earthworms. Look for leaves that have fallen in places earthworms cannot get to like pavements. Collect the leaves and take them to sheltered, open soil locations.

Try not to heap leaves too much in one place, spread them evenly so the earthworms don’t have to compete for space and take longer to break it down.

You could take pictures once a week to document the breaking down of the leaves. A good activity during Autumn.

Helpful resources

• Earthworm Watch. This citizen science project is complete but the page contains useful information and downloads about soil and earthworms. See also this external project page.

External Sites

• Learning More About Earthworms With Citizen Science - Article from Frontiers for Young Minds