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Australian primary science · Year 3 · Lesson 2 of 3
Soil your undies
Inquiry question: How can buried cotton tell us whether a soil is full of life?
Marked no materials needed
Pattern seeking
What students learn
Healthy soil is full of tiny living things that break down dead plant material. Farmers and scientists collect data, such as how much buried cotton is eaten away, to compare soils and explain why some are healthier than others.
Success criteria
- I can read how much cotton was left at each site.
- I can find the soil with the most life and the soil with the least.
- I can use the data to explain which soils are healthiest and why.
Preparation and materials
Before this lesson: Students know soil contains rotting plant material and living things (lesson 1).
- One screen or projector to show this lesson’s student view (the buried cotton data) (or print one student view per pair) — 1
- Workbooks or scrap paper, and pencils — 26
Teacher setup
- Open this lesson’s student view (the buried cotton data) on your screen, or print the student view if the internet is unreliable.
- No other preparation is needed.
Safety and adaptations
Follow school science and equipment risk assessment procedures for the materials used.
Review your school policies and curriculum requirements before teaching.
How to investigate
The lesson sequence should leave pupils with evidence to interpret, not only an activity to finish.
- Pairs read the data table in the student view.
- Rank the six sites from least cotton left (most soil life) to most cotton left (least soil life).
- Look at the “What people saw” column. What do the sites with the least cotton left have in common?
- Write a pattern sentence: “The more ___, the less cotton was left.”
- Discuss: why did everyone use the same cotton and bury it for the same time?
Teacher modelling prompt
Point to the vegie garden row. Think aloud: “10% of the cotton was left, so 90% was eaten away. And they saw lots of worms. Now the hard path: 90% left, almost nothing eaten, and no animals seen. So more life in the soil means less cotton left.” Write the pattern sentence.
Record and explain evidence
Recording question: How can buried cotton tell us whether a soil is full of life?
| Place | Cotton left after 8 weeks | What people saw in the soil | Rank (1 = most soil life) |
|---|---|---|---|
| ________________ | ________________ | ________________ | ________________ |
Example recording headings; record actual observations, including inconclusive results.
Discussion prompt
Which claim does the data support?
Provided example or reference data
Example data: how much of a buried 100% cotton strip was left after 8 weeks (made up for this lesson, similar to results from Australia’s “Soil Your Undies” challenge)
| Place | Cotton left | What people saw when they dug it up |
|---|---|---|
| Vegie garden with compost | 10% | Moist, dark soil; many worms and slaters |
| Bushland under trees, thick leaf litter | 25% | Damp leaves; fungus threads, beetles |
| Grassy paddock | 40% | Some worms and roots |
| Mown lawn on the school oval | 55% | A few roots, two worms |
| Dry sandy paddock during a drought | 85% | Very dry; no animals seen |
| Bare, hard-packed path | 90% | Hard to dig; no animals seen |
Check the data source in the teacher lesson. Illustrative or fictional data are not measurements collected by your class.
Check understanding
What should pupils know? Why does cotton break down faster in some soils than others?
Explain with evidence: The bush soil had 25% left and the oval had 55% left. Which soil has more life? Use the numbers.
Apply the idea: A farmer’s cotton came back almost whole. What could she do to bring more life into her soil? Stretch (older students): how could she use buried cotton to check whether her change worked?
Teacher answer guidance and saved classroom work are available through the main lesson experience where supported.