Soil Tests Anyone Can Do at Home

You will need

• A clear jar with a lid (tall and straight-sided is best)
• About 1 cup of soil from your garden
• Water
• 1 teaspoon of dish soap (it helps the bits come apart)
• A marker and a ruler

Try it

1. Pick out rocks, sticks and roots.
2. Fill the jar one-third full of soil. Add water until it is two-thirds full, then the soap.
3. Put the lid on tight and shake hard for 3 minutes.
4. Set it down where it won't be bumped. After 1 minute, mark the top of the bottom layer: that's sand.
5. After 2 hours, mark the next layer: that's silt.
6. When the water clears (1 to 2 days), mark the top layer: that's clay.

What it means

Mostly sand

Water and food drain away fast. Compost helps it hold on.

Mostly silt

Smooth and rich, but it crusts and packs down when left bare.

Lots of clay

Holds water and food, but gets sticky and short of air. Roots and compost open it up.

About even

That's called loam, and most plants love it.

Floating bits

Bits of old leaves and roots: organic matter, food for soil life.

In Hawaiʻi: Volcanic soils can stay cloudy for days and the layers may look blurry. That's the ash, not a mistake.

Wonder: Which layer is the thickest in your jar?

You will need

• A small handful of soil
• A little water
• A ruler

Try it

1. Take a lump of soil the size of a ping-pong ball and pick out any stones.
2. Add water a few drops at a time, squeezing, until it feels like soft putty.
3. Rub a pinch between your fingers. Gritty means sand, silky (like flour) means silt, sticky means clay.
4. Squeeze the ball between your thumb and finger, pushing it up into a flat ribbon.
5. Keep pushing until the ribbon breaks off. Measure how long it got.

What it means

No ribbon, falls apart

Sandy soil.

Under 1 inch (2.5 cm)

A loam: a good mix.

1 to 2 inches (2.5 to 5 cm)

A clay loam.

Over 2 inches (5 cm)

Clay.

Try both: Do the Jar Test too. Your fingers and the jar should tell the same story.

Wonder: Which word fits your soil best: gritty, silky or sticky?

You will need

• Two clumps of soil about the size of a grape: one from a garden bed or under mulch, one from a bare path
• Two clear glasses of water
• Two forks, or two pieces of window screen

Try it

1. Let both clumps dry on a plate for a day.
2. Set each clump on a fork (or screen) and lower it gently into its glass, just under the water.
3. Watch for 5 minutes. Don't touch!
4. Then lift each one gently up and down a few times.

What it means

Holds together

Roots, fungus threads and the sticky stuff soil life makes glue the crumbs. Rain soaks in instead of washing soil away.

Falls into a muddy cloud

Not much glue. This soil needs living roots, mulch, compost and less digging.

Little bubbles

Air coming out of the spaces in the soil. That's normal.

Wonder: Which clump held together longer? What was growing where it came from?

You will need

• A metal can with both ends cut off (a grown-up's job; tape the sharp edges)
• A small board and a hammer
• A ruler, a marker and a timer
• A jug of water

Try it

1. Inside the can, draw a line 1 inch (2.5 cm) from one end.
2. Set the can on the soil, other end down. Lay the board on top and tap it in about 2 inches (5 cm).
3. Pour water in up to the line and start the timer.
4. Stop the timer when the water is gone and the soil just glistens.
5. Do it again in the same spot. The second time is your answer.

What it means

Under 10 minutes

Rain soaks in well. Lots of open spaces in the soil.

10 to 60 minutes

Slow. In a big storm, water may run off.

Over an hour

Packed down or crusted. Water runs off and roots run short of air.

Compare: Test a garden bed and a path. The difference is what feet and bare ground do to soil.

Wonder: Where in your yard does water sink in the fastest?

You will need

• A wire survey flag (from a hardware store) or a straight piece of stiff wire with tape on the end
• A ruler

Try it

1. Test a day after rain or watering. Dry soil always feels hard.
2. Hold the wire straight up near the top.
3. Push it straight down, slow and steady. Don't force it.
4. Stop when it bends or won't go any further. Pinch it at the soil line and pull it out.
5. Measure how deep it went. Try 5 spots: a garden bed, the lawn, a path, under a tree.

What it means

Slides past 12 inches (30 cm)

Loose and open. Roots and worms move easily.

Stops in the top few inches

A hard, packed layer. Roots and worms struggle to get through.

A sudden stop and a clink

Probably a rock. Try a spot nearby.

Helping hard soil: Stay off wet soil, keep paths in one place, mulch, and grow deep-rooted plants like daikon radish. Roots and worms open it up.

Wonder: Where in your yard is the soil hardest? Who walks there?

You will need

• A shovel
• A tarp or an old sheet
• A ruler

Try it

1. Pick a cool morning when the soil is moist.
2. Dig out a block of soil about 1 foot (30 cm) wide, long and deep. Set it on the tarp.
3. Break it apart gently with your hands and count every earthworm.
4. Put the soil and the worms back in the hole.

What it means

10 or more

Great! Plenty of food, air and water for soil life.

5 to 10

Good.

Fewer than 5

The soil may be too dry, packed down, low in organic matter, or dug or sprayed lately.

Good to know: Worms go deep when it's hot or dry. A low count on a dry day may not be the whole story. Try again after rain.

Safety: Wash your hands after.

Wonder: Where do you think the worms go when the soil dries out?

You will need

• A handful of soil from a garden bed
• A handful from a bare or soggy spot
• A little water

Try it

1. If the soil is dry, sprinkle on a little water.
2. Hold each handful close and take a gentle sniff.
3. Find a word for each smell: sweet, earthy, sour, rotten, or nothing?

What it means

Sweet and earthy, like a forest after rain

Soil life is busy. That smell is geosmin (jee-OHZ-min), made by tiny thread-like bacteria in airy, healthy soil.

Sour or like rotten eggs

The soil is too wet and short of air. Life that doesn't need air has taken over.

Nothing at all

Dry, or low in life. Wet it and sniff again. Still nothing? It needs organic matter.

Fun fact: Your nose can smell geosmin in tiny amounts. It's why the air smells so good when rain hits dry ground.

Wonder: Which handful smelled more alive?

You will need

• A spoonful of dry soil
• A small clear cup
• White vinegar
• A spoon

Try it

1. Put a spoonful of soil in the cup.
2. Pour in a few spoonfuls of vinegar.
3. Put your ear close and listen. Watch for bubbles.

What it means

Fizzes or hisses

The soil has lime in it: crushed coral, shell or limestone. It's probably on the basic side (pH above 7). Don't add more lime.

No fizz

No lime. Most Hawaiʻi volcanic soils don't fizz.

Good to know: This test finds lime, not the exact pH. Try the Red Cabbage pH Test, or bring a sample to Dr. Dirt's pH meter.

Safety: Vinegar stings eyes. Keep it away from faces.

Wonder: Does soil near the beach fizz more than soil up mauka?

You will need

• A funnel (or the top of a plastic bottle, cut off and flipped)
• A jar and a damp paper towel
• A piece of window screen
• A handful of leaf litter or crumbly compost
• A desk lamp and a magnifying glass

Try it

1. Put the damp paper towel in the bottom of the jar.
2. Set the funnel in the jar and lay the screen inside the funnel.
3. Put the leaf litter on the screen.
4. Shine the lamp about 6 inches (15 cm) above it. The critters crawl away from the light and warmth, down into the jar.
5. After 2 to 4 hours, look in the jar with the magnifying glass. Count and draw what you find.

What it means

Springtails

Tiny jumpers.

Mites

Tiny and round, with 8 legs.

Pill bugs, millipedes and beetles

The shredders.

Lots of kinds

A busy soil food web, turning leaves into food for the microbes.

Safety: The lamp gets hot: a grown-up sets it up, and never leave it on alone. Don't touch centipedes; they can pinch. Let the critters go where you found them.

Wonder: How many different kinds did you find?

You will need

• Two tea bags (green tea in a mesh bag lasts best), or a new pair of 100% cotton underwear
• A trowel and two marker sticks
• A kitchen scale, if you have one

Try it

1. Weigh each tea bag, or take a photo of the underwear.
2. Bury each about 3 inches (8 cm) deep in a different spot: a garden bed and a lawn or a bare spot. Mark each with a stick.
3. Wait 2 to 3 months.
4. Dig them up, brush off the soil, let them dry, then weigh or look.

What it means

Lots eaten (big holes, light tea bag)

Busy soil life: bacteria, fungi and worms at work.

Nearly whole

Slow soil life. It may be too dry, packed down or low in food.

Good to know: Soil life eats faster when it's warm and moist. Hawaiʻi's warm soil can work fast!

Safety: Wash your hands after.

Wonder: Which spot ate more? Why do you think so?

You will need

• Two red cabbage leaves and hot water (a grown-up's job)
• A strainer and coffee filters
• Clear cups and a spoon
• Distilled water or rainwater (tap water can change the color)
• For comparing: lemon juice, plain water, baking soda in water

Try it

1. A grown-up chops the leaves, covers them with hot water and lets it sit 10 minutes. Strain out the purple juice.
2. Mix 2 spoonfuls of soil with 4 spoonfuls of distilled water. Stir, then let it settle for 10 minutes.
3. Pour the soil water through a coffee filter into a clear cup.
4. Add a few spoonfuls of cabbage juice. Do the same with the comparing cups.

What it means

Pink

Acid (sour), like lemon juice.

Purple

About neutral, like plain water. Most garden plants like slightly acid to neutral soil.

Blue or green

Basic, like baking soda.

Good to know: Colors change gently in soil, so it's a rough guide. For the exact number, Dr. Dirt uses a pH meter.

Wonder: Predict first: what color will your soil turn?