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It all comes down to pore space.
Healthy turf doesn’t start with the grass — it starts with the structure of the soil underneath it. Here’s what that means.
The basics
What compaction actually is.
Soil isn’t solid. Good soil is roughly half solid particles and half open space — and that open space, called pore space, is where water, air, and roots actually live. When soil is compacted, those pores collapse. The solid particles press together into a dense mass, and water, air, and roots lose the room they need to move.
The value of any topsoil comes down to its physical structure. Along with nutrients, a soil needs a continuous supply of both air and moisture. Poorly structured soil waterlogs in wet seasons and dries out too fast in dry ones — and in both cases, the plant suffers.
Why clay soils are the worst offenders
Clay particles are extremely fine. Under traffic, salts, and time, they pack together into a tight, low-oxygen layer that roots physically can’t push through. In alkaline and sodic soils, excess salts make it even worse — sodium disperses the clay and locks it into a compacted mass with almost no connected pore space.
Aggregates: the fix soil wants
The goal isn’t to remove the clay — it’s to get those fine particles to bind together into larger clumps called aggregates. When fine particles aggregate, the gaps between the clumps become connected pathways. Air and water move freely, and roots follow.
A useful way to picture it: a jar of packed sand versus a jar of marbles. Same volume of material, but the marbles leave large, connected gaps for air and water to pass through. Aggregation turns packed “sand” back into “marbles.”
Two kinds of pores, two different jobs
Well-structured soil has both capillary pores (small, they hold water against gravity) and non-capillary pores (large, they let water drain and air in). Compacted soil loses the large pores first — which is why it both floods and dries out. Rebuilding structure restores both, so soil drains after heavy rain and holds moisture longer between waterings.
Why mechanical aeration only goes so far
Core aeration physically pulls plugs to open holes — but it only reaches an estimated 3–5% of the surface, and it doesn’t change the structure of the soil in between. The holes close, the compaction returns, and the underlying clay is unchanged. To fix compaction, you have to change the soil itself.
See it
Compacted vs. aggregated soil.
On the left, fine particles are packed tight with almost no room between them. On the right, those same particles have bound into larger aggregates — opening the connected pore space that lets water, air, and roots move through.
How SoilTech does this