The Jar Test (Soil Texture)

Separate your soil into sand, silt, and clay to classify its type. Takes about 48 hours total, but only 5 minutes of hands-on work.

Dig a small hole 200mm deep and collect a handful of soil
Remove rocks, roots, and debris
Fill a clear glass jar one-third full of soil
Add water to two-thirds full, then add 1 teaspoon of dish soap
Shake vigorously for 2 minutes, then set on a flat surface
Wait and observe: After 1 minute — sand settles to the bottom. Mark the line.
After 2 hours — silt settles on top of sand. Mark the line.
After 24-48 hours — clay settles on top. Mark the line.
Anything floating is organic matter.
Measure the height of each layer in millimetres

Enter the height of each layer as it appears in your jar.

Total soil height (mm)

Sand layer (mm)

Silt layer (mm)

Clay layer (mm)

The Infiltration Test (Infiltration Rate)

Measure how fast water soaks into your soil. This tells you which earthworks will actually function on your site.

Remove both ends from a large tin can (coffee can or similar, roughly 150mm diameter)
Push the can 50mm into the ground at your test site
Fill the can with water to the top and let it drain completely — this pre-saturates the soil
Refill the can with water to the top
Start a timer
Measure how far the water level drops over your test period (use a ruler inside the can)
The drop in mm, normalised to one hour, is your infiltration rate in mm/hr

Enter your measurements below.

Water drop (mm)

Test duration

Can diameter (mm)

Earthwork	Suitability

Soil Result	Best Earthworks	Avoid
Sandy / Fast infiltration (>25 mm/hr)	Swales, infiltration basins, keyline ripping	Unlined ponds
Loam / Medium infiltration (5–25 mm/hr)	Swales, keyline ripping, ponds (compacted base), diversions	—
Clay / Slow infiltration (<5 mm/hr)	Ponds, diversion drains, contour berms	Infiltration swales near structures

Test multiple locations on your property — soil varies significantly even over short distances.

Test at the depth you plan to build (200-500mm), not just the surface. Subsoil texture often differs from topsoil.

Test after dry weather for worst-case infiltration rates. Your driest result is the one to design around.

Wet-season results will be slower due to saturated soil. If you find different soil types, design different earthworks for each zone.