What is soil made of?

Science · Earth's Systems · ages 7-8

Name ______________________ Date ____________

Sandy soil usually feels gritty.
Circle one: True False
Which pair names two ingredients found in soil?
- Mineral particles and organic matter
- Only large stones and no decayed material
- Only living worms and no mineral particles
What is humus?
- Fresh rock particles made by breaking a stone
- Well-decayed organic matter
- Water frozen between the particles in soil
Why does clay soil usually stay wet longer than sandy soil?
- Its small particles and spaces hold water.
- Its particles leave much wider spaces than sand does.
- It contains no mineral particles and is made only of humus.
In this new made-up test, equal soil samples receive equal water. Which lets the most water drain through in 4 minutes? The bars show collected water in mL.
- Clay soil
- Loam soil
- Sandy soil
A gardener wants soil that holds some water but lets extra water drain. Which soil often suits this need?
- Soil made entirely of coarse sand
- Soil made entirely of fine clay
- Loam soil
Which description identifies the mineral-particle mixture in loam?
- Only sand particles, with no silt or clay
- A mixture of sand, silt and clay
- Only clay particles, with no sand or silt
Ravi says a whole rock becomes developed soil after one rainy week. Which fact checks his idea?
- Soil development takes much longer than a week.
- Rain turns any whole rock into finished soil within seven days.
- Developed soil contains only rock and never any organic matter.

Answer key

For grown-ups. Fold this page away before handing over the rest.

True · Gritty describes the feel of sandy soil. Wet clay can feel smooth and sticky instead.
Mineral particles and organic matter · Soil contains mineral particles and organic matter, along with air, water and living organisms.
Well-decayed organic matter · Humus is well-decayed organic matter from once-living things.
Its small particles and spaces hold water. · Clay's small spaces hold water. It usually drains more slowly than sandy soil.
Sandy soil · The sandy sample lets 8 mL through, more than loam's 6 mL or clay's 3 mL.
Loam soil · Loam often suits garden plants because it can hold some water while letting extra water drain.
A mixture of sand, silt and clay · Loam contains sand, silt and clay particles. Humus may also be present, but it does not define this particle mixture.
Soil development takes much longer than a week. · Soil develops over a long time as weathered particles mix with decaying material and other changes occur.