What is hydrophobic soil?
Quick answer
Hydrophobic (water-repellent) soil sheds water instead of soaking it up. A waxy or oily coating on soil particles, common on sandy soils that dry out, makes water bead on the surface or run off, so patches stay dry even after watering. A wetting agent, applied at the label rate and watered in, helps water soak in again.
Why this happens
Hydrophobic means “water-fearing”. Water-repellent soil develops a waxy or oily coating on its particles, especially sandy soil that has dried out. Instead of soaking in, water beads on the surface or runs off to the lowest point. Water Corporation describes how WA sands, in particular, can have an oily film on the grains that pushes water away.
The result is a lawn that browns in patches even though you’re watering. The water simply isn’t reaching the roots. The more the patch dries, the worse the repellence gets, so the problem builds through summer.
How to tell
Pour a cupful of water onto a dry patch. On healthy soil it disappears within seconds. On hydrophobic soil it sits there as beads or a puddle, or runs off. Then push a trowel in: if the soil is dry a few centimetres down right after watering, water isn’t getting in.
Check two other causes before treating: uneven sprinkler coverage (a catch-cup test shows it) and lawn grubs (lift a piece of turf at the edge of the patch).
How to fix it
A wetting agent helps water soak into repellent soil. Apply it at the label rate, water it in, and re-apply as the label directs. On WA sands, Water Corporation suggests applying wetting agents several times a year. Getting the first application on in spring, before the soil dries right out, works better than rescuing a lawn in mid-summer.
Core aerating compacted patches helps water in too, and once water is soaking in again, deep and less frequent watering keeps the soil from drying out completely.
What you may be seeing
- Brown, dry patches that don't green up after rain or watering
- Water beading or sitting on the surface before running off
- Dry soil a few centimetres down, even right after watering
What you can do
Do the water drop testCheck first
Pour a little water on a dry patch. If it beads or sits on top instead of soaking in, the soil is water-repellent.
Rule out sprinkler coverageCheck first
Do a catch-cup test. If the patch gets much less water, fix the sprinklers first.
Aerate compacted areas
Coring opens up compacted soil so water can get in.
Water deeply
Once water is soaking in again, water deeply and less often.
Apply a wetting agentProduct step
Use a lawn wetting agent at the label rate and water it in. Repeat as the label directs through the warm months.
What not to do
- Simply watering longer, which runs off without wetting the soil.
- Waiting until mid-summer, when the soil is already bone dry.
How much do I need?
A label rate of "20 mL per 100 m²" means: Rate 20, mL, per 100 m². Per hectare? Use 10,000 m².
How much you need
Enter your lawn area and a rate to see how much product and water you need.
Log it
Keep a record of what you applied, when, and at what rate. Your Lawn Journal works on this device without an account, and reminds you when the next step is due.
What's next
Related grass types, weeds, pests and diseases
Lawn problems
Related questions
Related guides
- Application guideHow to use a hose-end sprayer
- Application guideHow to apply a lawn wetting agent
- Irrigation guideThe catch-cup test: measure what your sprinklers actually put out
- Irrigation guideHow much water does a lawn need?
- Irrigation guideHydrophobic soil: why water won't soak in, and how to fix it
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Sources
- Bring your brown lawn back to life, Water Corporation (Western Australia)WA sands are often hydrophobic: an oily film on sand grains pushes water away; wetting agents; uneven watering; aeration. Accessed 4 October 2026.