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Why won't part of my Toowoomba lawn soak up water?

How to tell if that's what's happening

Fill a watering can and pour it slowly onto the dry patch. On healthy soil it disappears within a few seconds. On hydrophobic soil it sits there in beads, then runs sideways to the nearest low point — usually leaving the patch as dry as it started.

Two more signs worth checking. Dig out a small plug with a trowel: if the top few centimetres are bone dry but it's damp underneath, water has been running off rather than in. And if the dry patches keep reappearing in the same spots — usually on slopes, along the north-facing side, or where the sun hits hardest — that's repellency, not an irrigation gap.

Why Toowoomba's red soil does this

Most of Toowoomba sits on deep red Ferrosol — the iron-rich basalt soil (older locals call it krasnozem) that runs up the range through Highfields, Rangeville, Middle Ridge and Newtown. It's genuinely excellent soil: well structured, free draining, good depth.

That free drainage is exactly what causes the problem. When the surface dries out hard over summer, waxy organic compounds from decomposing roots and thatch coat the soil particles. Those waxes repel water. The drier it gets, the worse the coating, and the worse the coating the drier it gets — which is why a patch that starts small tends to spread through January and February.

Sloped blocks suffer most, because water that doesn't soak in immediately has somewhere to go.

What actually fixes it

A soil wetting agent. These are surfactants — they reduce the surface tension of water so it can penetrate the waxy coating instead of beading on top of it. Applied properly and watered in, you'll usually see the patch start absorbing within a week or two.

• Apply in early spring, before the summer heat sets the repellency in, and again mid-summer if the patches return
• Water it in thoroughly — a wetting agent left sitting on the surface does nothing
• Pair it with core aeration so the water that's now absorbing can actually reach the root zone
• Raise your mowing height over summer — longer leaf shades the soil and slows the drying that starts the whole cycle

What doesn't fix it

Watering more. It feels like the obvious answer, and it's the most common thing we see people try — but water that can't penetrate just runs off, whether you give it five minutes or fifty. You'll raise your water bill without changing the patch.

Fertilising won't fix it either. If the soil isn't taking water, it isn't taking dissolved nutrients either — you're feeding a lawn that can't eat. Get the soil absorbing first, then feed it.

Is it different on black soil?

Yes. If you're on the black cracking clay found in the lower parts of the region — Westbrook, Wyreema, out toward Cambooya and the flats — water pooling on the surface usually means compaction, not repellency. Same symptom, different cause, different fix: that one wants aeration and coring rather than a wetting agent.