E. Earth and Space Systems · Soils in the Environment

Sand, Silt, Clay and Loam

E2.3 A1.2 A1.5 A3.2About 45 minutes

Learning goals

I can describe sand, silt, clay and loam by how they look and feel.
I can test how well different soils hold and drain water using a fair test.
I can use measurements to compare soils.
I can explain why loam is good for growing most plants.

Words to know

sand
The biggest bits of rock in soil. Sand feels gritty, and water drains through it quickly.

silt
Medium-sized bits of rock, too small to see one by one. Dry silt feels smooth, like flour.

clay
The tiniest bits of rock in soil. Wet clay is sticky and can be shaped. Clay holds a lot of water.

loam
A soil that is a good mix of sand, silt and clay, with plenty of humus. Most plants grow well in loam.

drain
When water flows through and out of something.

fair test
An experiment where you change only one thing and keep everything else the same.

Sandbox, mud pie or garden?

Think about three places: a sandbox at the park, a mud pie you can shape with your hands, and the dark soil in a vegetable garden. They are all made of soil, but they look and feel very different!

The biggest difference is the size of the bits of rock in them.

Bits of rock come in three main sizes. Sand bits are the biggest. Silt bits are medium. Clay bits are the tiniest (much tinier than this drawing shows).

Meet the soil family

Sand has the biggest bits. You can see the grains. It feels gritty. Water drains through it fast, so sandy soil dries out quickly. It does not hold many nutrients. When you squeeze damp sand, it falls apart.
Silt has medium bits, too small to see one at a time. Dry silt feels smooth and soft, like flour. Wet silt feels silky and slippery. It holds more water than sand.
Clay has the tiniest bits. Wet clay is sticky and you can shape it, like play dough. Clay holds lots of water and drains very slowly, so it can get soggy. When it dries, it can get hard and cracked.
Loam is a mix of sand, silt and clay, with plenty of humus. It holds enough water for plants, but extra water can drain away. It is crumbly. Most garden plants grow best in loam.

Most real soils are a mix. We name them by which kind there is most of, like "sandy soil" or "clay soil".

A white tray with three piles: light gritty sand, smooth grey clay and dark crumbly loam. — Compare the gritty grains of sand, the smooth, sticky clay that holds its shape, and the dark, crumbly loam full of humus. AI-generated image

	Sand	Silt	Clay	Loam
Size of bits	biggest	medium	tiniest	a mix
Feels like	gritty	smooth, like flour	sticky when wet	crumbly
Water drains	very fast	medium	very slowly	medium
Holds water	very little	some	a lot	a good amount
Squeeze test	falls apart	ball breaks easily	makes a ball and a long ribbon	makes a ball that crumbles when poked

Comparing soil types

Worked example

Let's test by feel: the squeeze test

Arjun has three cups of damp soil labelled A, B and C. How can he tell which is sandy, which is clay and which is loam?

He takes a spoonful of each, adds a few drops of water and squeezes it in his hand (with gloves).
Soil A feels gritty and falls apart when he opens his hand. That is sandy soil.
Soil B makes a ball. When he pokes it, it breaks into crumbs. That is loam.
Soil C is sticky. He can roll it into a long ribbon that bends without breaking. That is clay soil.

A is sandy, B is loam, C is clay. He used the sense of touch to compare them.

Worked example

Let's do a fair test: Which soil holds the most water?

Ella wants to know which soil holds the most water: sand, loam or clay. How can she make it a fair test?

Question: Which soil holds the most water? Prediction: "I think clay will hold the most, because its bits are tiny and sticky."
Change only one thing: the type of soil.
Keep the same: the same amount of soil (1 cup each, dry), the same kind of funnel and coffee filter, the same amount of water (100 mL), and the same time (5 minutes).
She pours 100 mL of water on each soil and measures the water that drips through into a measuring cup.
Sand let 80 mL through. Loam let 55 mL through. Clay let 20 mL through.
Water held by the soil = 100 mL − water that dripped through. Sand held 100 − 80 = 20 mL. Loam held 100 − 55 = 45 mL. Clay held 100 − 20 = 80 mL.

Clay held the most water (80 mL). Sand held the least (20 mL) and drained the fastest. Her prediction was correct.

Soil	Water poured in	Water that dripped through	Water held by soil
sand	100 mL	80 mL	20 mL
loam	100 mL	55 mL	45 mL
clay	100 mL	20 mL	80 mL

Ella's results after 5 minutes

Ella's results as a bar graph. Clay held the most water (80 mL) and sand held the least (20 mL).

Why does it matter?

Plants need water, but their roots also need air.

In sand, water drains away so fast that plants can dry out.
In clay, water can stay so long that the spaces fill up and roots can't get enough air. Hard, dry clay is also tough for roots to push through.
Loam is "just right" for most plants: it holds some water and still has air spaces.

But some plants like other soils. Next lesson you'll see how Ontario farmers grow different foods in different soils.

A soil jar after shaking and settling for a day. The heaviest bits (sand) sink first to the bottom. Silt settles in the middle. The tiniest bits (clay) settle last, on top. Bits of humus float on the water.

The soil jar test

You can see what is in your soil with a jar of water! Fill a clear jar about one-third with soil, add water until it is almost full, put the lid on tightly and shake for a minute. Then leave it alone for a day.

The biggest, heaviest bits sink first, so sand is on the bottom. Silt settles on top of the sand. Clay bits are so tiny that they take the longest to settle, so clay is on top. Light bits of humus float. Thick layers tell you which kind of soil you have most of.

Just for fun

Why is clay soil such a loyal friend?

Because it always sticks around!

Hands-on activity

Soil jar and drainage test

You need: a clear jar with a lid, soil from outside, water, a ruler. For the drainage test: 2 or 3 plastic cups, a sharp pencil or a nail (for a grown-up only), coffee filters, a measuring cup, and different soils (for example sand from a sandbox, garden soil, and potting soil).

Jar test

Fill the jar one-third with soil. Add water until almost full. Close the lid tightly and shake.
Wait one day. Draw the layers.
Use a ruler to measure each layer in centimetres. Which layer is thickest? What kind of soil do you have most of?

Drainage test

A grown-up pokes 5 small holes in the bottom of each cup.
Put a coffee filter in each cup and add the same amount of each dry soil.
Hold each cup over the measuring cup. Pour in 100 mL of water. Wait 5 minutes.
Record how much water came through. Subtract to find how much each soil held.
Make a bar graph of your results and tell someone what you found.

Safety: Wear gloves, or wash your hands with soap after touching soil.

Your turn

Which soil has the biggest bits? Which has the tiniest?

Which soil feels sticky when it is wet?

Which soil drains water the fastest?

What is loam?

You pour 100 mL of water into a cup of soil. 30 mL drips through. How much water did the soil hold?

In a soil jar, which layer ends up on the bottom? Why?

Name one thing you must keep the same in the water test to make it fair.

More practice: warm-up

Which soil feels smooth, like flour, when dry?

Which soil do most garden plants like best?

True or false: Clay holds a lot of water.

Which soil falls apart when you squeeze it?

What do bits of humus do in a soil jar?

More practice: on your own

Why do plants in very sandy soil often dry out?

Why can plants in heavy clay soil have trouble after lots of rain?

Soil X let 65 mL of 100 mL drip through. Soil Y let 25 mL through. Which soil held more water? How much more?

A soil jar has a thick bottom layer and very thin top layers. What kind of soil is it?

Why is loam called "just right" for most plants?

Challenge

Ben tests two soils, but he pours 100 mL on one and 200 mL on the other. Is it a fair test? Explain.

A soil jar is 12 cm of settled soil. Sand is 6 cm, silt is 4 cm and clay is the rest. How thick is the clay layer? Which kind is half of the soil?

Potters make bowls from clay, not sand. Use what you know about clay to explain why.

Check your understanding

Quiz

Which soil has the tiniest bits?

Water drains fastest through...

Which soil is best for most garden plants?

100 mL of water is poured on a soil and 40 mL drips through. How much did the soil hold?

In a fair test about which soil holds more water, what should you change?

Which soil makes a long, bendy ribbon in the squeeze test?

For parents and teachers

Big idea (E2.3, part 1): Soil texture depends on particle size: sand (largest, gritty, fast-draining), silt (medium, floury), clay (smallest, sticky, water-holding). Loam is a balanced mix with organic matter. These properties decide what grows well, which leads into the next lesson on Ontario soils and foods.

How to help: The drainage test is a real fair test (A1.2) and a measurement and subtraction task (math connection, A3.2). Have your child say what changed and what stayed the same, and share results with a bar graph (A1.5). Potting soil from a store works as a stand-in for loam; sandbox sand for sand; for clay, dig in the subsoil in many parts of southern Ontario, or use any natural modelling clay softened with water.

Common difficulties:

Mixing up "drains" and "holds". Sand drains fast and holds little; clay drains slowly and holds a lot. These are opposites.
Subtraction order. Water held = water poured in − water that came through.
Jar test patience. Clay can take a day or more to settle; the water may stay cloudy at first.

Safety: Only an adult makes holes in cups. Keep jar lids tight while shaking. Gloves or hand-washing with soap after handling soil.