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Grow It 3-5 / Week 09 / Tuesday
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Week 09 · Soil and Decomposers

Tuesday

Sand, silt and clay
// What soil is made of, and who recycles it
⏱ about 15 min

Tuesday: Sand, Silt and Clay

Rocket rubs wet soil between his gloved fingers. "Some feels gritty. Some feels smooth," he says.

Raven holds up a clear jar of water. "What do you notice if we shake soil in here?"

Rocket grins. "A soil snow globe!"

Nova hovers by the jar. "Watch what sinks first," she says. "Size might be a clue."

Three sizes of rock bits

Sand bits are the largest. You can see them without a magnifier.

Silt bits are smaller.

Clay bits are the smallest. They are 1,000 times smaller than sand bits!

Most soils have a mix of all three.

Rock bitSizeHow it feels
sandlargestgritty
siltmiddlesmooth, like flour
claysmalleststicky when wet
BIGGEST TO SMALLEST
  • Tap a card.
  • Then tap its spot.
1Biggest
2Middle
3Smallest

The shake jar test

Shake soil in water, and the bits settle out by size.

Sand is heaviest, so it settles first, in about a minute.

Silt settles on top of the sand in a couple of hours.

Clay takes several days. It makes the top layer.

  • A clear jar with a tight lid
  • Garden soil (a grown-up digs it)
  • Water
  • Gloves and a marker
Safety first
A grown-up digs the soil and fills the jar one-third full.
Wear gloves when you touch soil.
Check that the lid is tight before you shake.
Wash your hands after.
  1. Add water until the jar is almost full.
  2. Close the lid tight.
  3. Shake the jar hard for a few minutes.
  4. Set it down where it can sit still for days.
  5. After one minute, mark the sand layer on the jar.
PREDICT THE LAYERS
  • Read the question.
  • Tap your answer.
Which layer will settle at the very bottom?
Which layer will be on top?
Which soil bit is the smallest? Type one word.
WHY THIS EXERCISEClay bits are the smallest, about 1,000 times smaller than sand.
StatementTrue or false?
Sand bits are the largest.?
Clay settles first in the jar.?
You can see sand bits without a magnifier.?
Clay can take several days to settle.?
WHY THIS EXERCISESoil bits settle by size: sand, then silt, then clay.
Try it
Check your bean plant and its soil.
Rub a pinch of its potting mix between gloved fingers. Gritty or smooth?
Write it in your plant log.

Nice shaking! Leave the jar alone. Tomorrow we meet the tiny workers that recycle soil.

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