Teacher instructions

Work through this resource material in the following sequence:

10 minutes

Tune in: Activating prior knowledge about topsoil

15 minutes

Find out: Explicit Teaching - Earth As An Apple Demonstration

25 minutes

Take action: Measuring shapes in the real world

Tune in: Activating prior knowledge about topsoil

Step 1. Discuss:

What is topsoil?
Where can you find it?
Why do you think it might be important for the earth?
Why do you think it might be important for animals?
Why do you think it might be important for humans?

Find out: Explicit Teaching - Earth As An Apple Demonstration

Step 1.

Take out your apple and invite students to imagine that the apple is Earth. Follow the Earth as an apple - demonstration instructions.

Step 2.

Explain to students that topsoil is the upper, outermost layer of soil. It is usually between 5 and 20 cm thick, depending on location, and has the highest concentration of organic matter (decaying plants and animals) and microorganisms.

Healthy topsoil is required to grow many of the food plants that humans depend upon (although most farmers use fertilisers to improve soil quality and plant productivity). Plants generally concentrate their roots in this soil layer and obtain most of the nutrients they need from topsoil. This limited amount of land is required to provide nearly everything we need to survive, and it takes 100 years to make just 1 inch of topsoil!

Step 3.

Discuss (also available on the Student Worksheet):

What did you see in the demonstration?
What did it make you think about?
What did it make you wonder about?
What questions does it leave you with?

Take action: Topsoil testing

Step 1.

Explain to students that they will now be investigating the topsoil around their school. They will be doing this by digging small holes at various sites around the school and measuring the depth of topsoil.

Explain to students that topsoil is generally darker than the soil beneath it due to the impact of organic matter that has incorporated itself into this layer. Therefore, when testing the depth of topsoil it will be necessary to dig to the layer below the topsoil.

Using the map of your school, identify locations around the school where you would like to test the topsoil. Where possible, include locations that are relatively undisturbed (such as areas of native vegetation) and areas that have experienced significant disturbance (such as around buildings or on the oval). Mark these locations on the map and number each location.

Step 2.

Break the class into groups and divide your soil testing locations between groups, with a maximum of four sites per group. Give each group a spade/shovel, a tape measure and a copy of the record sheet, and a pen/pencil. In addition, give each group a printed copy of the map of your school and ask each group to note the locations they have been assigned.

Step 3.

Groups should test the depth of the topsoil at all the locations they have been assigned, and record relevant information on the record sheets. Ensure students understand the importance of causing minimal disturbance to the soil and replacing soil once they have recorded their information.

Step 4.

Create a table on the board like the one below:

Site number	Depth of topsoil	Features of topsoil	Organisms present	Poor or good quality? Why?

Invite each group to add the data they collected to the table.

Step 5.

Working in the same groups as earlier, invite students to conduct an analysis of the class’s data using the following questions (also available on the Student Worksheet).

Where the topsoil the thinnest?
What might be some of the reasons why there is little topsoil here?
Where is it the thickest?
What might be some of the reasons why there is more topsoil here?
What evidence of organic matter did you see in the topsoil?
What other things might have affected the quality of the topsoil (rocks, sand etc)?
How did the quality and/or depth of topsoil affect what was growing there?
What evidence did you find to support your answer?
How can you tell if topsoil is healthy or not?
What evidence did you find to support your answer?

Engage students in a brief discussion around their answers.

Step 6.

Explain to students that they will now be working in their groups to develop a plan for improving the topsoil quality at their school.

Each group needs to create a map of their school showing:

The sites where topsoil quality could be improved
One priority site where action should be undertaken and justification for selecting this site
Actions that can be taken to improve soil quality (e.g. mulching, green manure planting etc) and justification for choosing these actions
Optional - incorporate photos of topsoil samples

Groups may need to undertake research online to identify the best actions to take to improve soil quality at their site.

Reflection

Discuss (also available on the Student Worksheet):

What do you think the relationship between topsoil and food production is?
What do you think the relationship between topsoil and biodiversity is?
If all the topsoil in the world disappeared how would this affect me?
What questions do I still have about topsoil?

Outdoor Learning - Topsoil Testing

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