What Soil Is Made Of

Sand, silt, clay and the life in between

4 minBeginnerUpdated 2026-10-23 What Soil Is Made Of

You will learn

Tell sand, silt and clay apart by touch
Explain why organic matter matters more than soil type
Do a jar test and a squeeze test in your own garden

⚠️ Wear gloves when handling soil and wash hands afterwards, especially before eating.

Three mineral parts

Every soil is a mix of three mineral particles. Sand is the largest, about 0.05 to 2 mm, and feels gritty. Silt is finer, like flour, and feels smooth or silky when wet. Clay particles are tiny, under 0.002 mm, and feel sticky. The mix of these three decides how fast water drains, how much the soil holds, and how easy it is to dig. Sandy soil drains fast and dries out quickly. Clay soil holds water and nutrients but goes rock hard in summer and sticky in winter. The ideal garden soil, called loam, is roughly 40 percent sand, 40 percent silt and 20 percent clay. Most gardens are not loam, and that is fine. You work with what you have.

💡 Rub a pinch of wet soil between your fingers: gritty means sand, silky means silt, sticky means clay.

The squeeze test

Take a handful of moist soil, not soaking, and squeeze it into a ball. Open your hand. If it falls apart at once, you have sandy soil. If it holds a ball but crumbles when you poke it, you have loam or a sandy loam, which is great news. If it holds a firm ball and you can press it into a ribbon between thumb and finger, you have clay. A ribbon longer than 5 cm means heavy clay. This test takes 30 seconds and tells you more than most soil kits. Do it in three or four spots, because soil changes across even a small plot.

The jar test

Fill a straight-sided glass jar one third with soil from 15 cm down, then top up with water and a teaspoon of dish soap. Shake hard for two minutes and set it down. Sand settles in about one minute. Silt settles over the next two hours. Clay stays cloudy and can take two days to settle fully. Once clear, measure each layer with a ruler. The proportions tell you your soil texture. Anything floating on top is organic matter. A thick floating layer is a sign of healthy soil. A thin one means your first job is adding compost.

Organic matter and soil life

The mineral part is only the skeleton. What makes soil grow food is organic matter: decomposed leaves, roots, manure and compost, plus the living things that eat it. One teaspoon of healthy soil holds more bacteria than there are people on Earth, along with fungi, earthworms and insects. They glue particles into crumbs, open channels for air and water, and release nutrients plants can absorb. Sandy soil with 5 percent organic matter holds far more water than sandy soil with 1 percent. Clay with plenty of organic matter drains and digs much better. Whatever your texture, adding organic matter is the fix.

💡 Count earthworms in a spade of soil. Ten or more is a healthy sign.

Soil pH in plain terms

pH measures how acid or alkaline soil is, on a scale from 0 to 14. Most vegetables grow best between 6.0 and 7.0, slightly acid to neutral. Blueberries want 4.5 to 5.5. Brassicas such as cabbage prefer closer to 7. Outside the right range, nutrients are locked up even if they are present. A cheap probe or test strip from a garden shop gives a rough reading. To raise pH, add garden lime in autumn. To lower it, add sulfur or plenty of pine needle compost. Change pH slowly, over seasons, never in one dose.

Check yourself

Which soil particle feels sticky when wet?

Clay particles are tiny and hold water on their surfaces, which makes wet clay feel sticky and lets it form a ribbon.

In the squeeze test, soil that forms a ball but crumbles when poked is most likely:

Loam holds together enough to ball but crumbles easily, which is the balance gardeners want.

In the jar test, which layer settles first?

Sand is the heaviest and largest particle, so it drops to the bottom within about a minute.

What is the best pH range for most vegetables?

Between 6.0 and 7.0 the widest range of nutrients is available to plant roots.

Try it for real: Test your soil three ways

Do the squeeze test in three different spots of your garden or a nearby patch of ground
Run a jar test with soil from 15 cm deep and wait two days
Measure the sand, silt and clay layers and write down your rough percentages
Count the earthworms in one spade of soil