Tow-Behind Aerators · How-To Guide
How Many Passes with a Tow-Behind Aerator? (And When to Do More)
One pass is almost never enough. A tow-behind aerator produces roughly half the plugs per square foot of a powered walk-behind in a single pass — and the fix isn't more weight, it's more passes. Here's the framework for knowing exactly how many your lawn needs.
The confusion starts with expectations set by rental experience. A rental gas-powered core aerator — a Ryan, a Billy Goat, a Husqvarna — pulls 9 or more plugs per square foot in a single pass thanks to powered tine drives and the machine's significant weight. One pass and the lawn is done.
A homeowner tow-behind aerator works differently. The tines are unpowered, spread across a wide frame, and rely on gravity for penetration. A 48-inch tow-behind with 32 tines crossing a square foot of lawn produces roughly 5–8 plugs per square foot per pass under good conditions. Iowa State Extension puts the target for a properly aerated lawn at 20 to 40 holes per square foot, and notes most core aerators won't reach that in a single pass. That gap — one pass delivering perhaps a quarter of the target — is why multiple passes are standard practice rather than optional. It is also why the honest answer to this page's title is uncomfortable: more than two.
The baseline: two passes at 90 degrees
Two perpendicular passes — north-south first, then east-west — is the standard starting point for tow-behind aeration. This pattern ensures new holes are punched in the gaps between the first pass's plugs rather than overlapping them, effectively doubling plug density across the lawn. After two passes on average residential loam you should see roughly 10–16 plugs per square foot. Note what that means against Iowa State's 20–40 target: two passes gets you halfway. Two is the realistic minimum, not the finish line — and three or four crossing passes is what actually lands in the extension range.
The 90-degree angle is important. A second pass in the same direction as the first sends the tines along nearly the same path, producing marginal additional coverage. Perpendicular passes fill in the gaps. Some operators use diagonal passes (45 degrees) for the second run — this works too, and can be easier to manage on irregular lawn shapes.
After two passes, pick a random square foot and count the plug holes. Iowa State's target is 20–40 per square foot; if you're well under that, keep making crossing passes. Most people stop too early because the lawn already looks worked over — count rather than eyeball it.
How many passes by situation
| Situation | Passes | Pattern |
|---|---|---|
| Well-maintained lawn, aerated annually, loamy soil | 2 | N-S then E-W |
| Average residential lawn, last aerated 2–3 years ago | 2–3 | N-S, E-W, then diagonal if 3rd needed |
| Compacted clay, never or rarely aerated | 3–4 | Two sessions recommended — 2 passes, rest 2 weeks, 2 more |
| Overseeding preparation (need maximum seed contact) | 3–4 | N-S, E-W, diagonal — more plugs = better seed-to-soil contact |
| Renovation (bare or heavily thinned lawn) | 4+ | Multiple sessions over the season |
Why two passes is the minimum — not a guideline
This is the part most tow-behind aerator guides gloss over. A single pass with a tow-behind on a large residential lawn produces a plug hole every 6–8 inches, roughly. That's compaction relief, but it's modest — the soil between the holes is still effectively untouched. At this density, water and nutrients penetrate better than in completely unaerated soil, but the improvement is incremental. Overseeding on a single-pass tow-behind aeration produces results noticeably thinner than the same seeding on a double-pass or walk-behind aeration.
Two passes changes the calculus. At roughly 10–16 plugs per square foot, the compaction relief is meaningful across the whole surface rather than in isolated channels — though still short of the extension target, which is the argument for a third pass wherever it matters. Seed dropped onto a double-pass aeration falls into plug holes regularly enough to produce good contact and germination rates comparable to walk-behind aeration results.
Why the second pass often produces better plugs
A frequently observed (and almost never written about) phenomenon: the second pass often pulls longer, cleaner plugs than the first pass on the same soil. The reason is mechanical. The first pass creates channels through the compacted soil — pathways of slightly reduced resistance. On the second pass, even when the tines are striking new spots between the first pass's holes, they're working in soil that's been slightly loosened and redistributed by the first pass. The result is better penetration depth and cleaner plug ejection on pass two.
This is one reason experienced tow-behind users prefer two passes at proper weight rather than one pass at maximum weight — the second pass benefits from what the first did, and produces better plugs without straining the tray or hitch with excessive ballast.
How soil type changes the answer
Soil type is the biggest variable in pass count. Sandy loam that aerates easily and has been maintained well may be adequately treated in two passes — plugs pull cleanly, the holes are spaced well, and the soil is visibly more open after the session. Heavy clay that's been compacted for years is a different project entirely.
In severely compacted clay, two passes may not be enough to reach the 10-plug-per-square-foot threshold because the tines struggle to penetrate to full depth consistently. The right approach here is not four consecutive passes in one afternoon — it's two passes today, then two more passes in two to four weeks after the soil has had time to settle and the existing plug holes to decompose slightly. The second session works into soil that was already disturbed by the first, and plug quality improves substantially. After two sessions, annual maintenance aeration needs only two passes to hold the improvement.
More than four or five passes in a single session risks loosening the soil to the point where turfgrass roots lose their anchor. On soft or already-moist soil, the bigger risk is tractor ruts — the mower's weight repeatedly crossing the same ground will compact and scar the turf surface. Stop when wheels are noticeably sinking or when the soil surface looks churned rather than cleanly punched.
How pass count relates to your specific aerator
The Ohio Steel 48CP's patented spring-assisted tines are real — that's Ohio Steel's own term. But it's worth being accurate about what the springs do, because it isn't extra force. Ohio Steel says the springs let the tines articulate, producing more defined holes and cleaner plug ejection, and they describe the machine as gentler on the lawn rather than harder-hitting. Their published aeration depth is up to 2.5 inches — shallower than the 3 inches Brinly and Agri-Fab claim. So the 48CP's advantage is plug quality per hole, not fewer passes. You still count holes and keep going.
The Brinly PA-403BH's individually replaceable tines mean that as tines wear, individual ones can be replaced rather than replacing the whole unit. Worn tines don't penetrate as well — if you're finding your plug depth declining over seasons despite good moisture and adequate weight, check tine sharpness before increasing pass count. The Brinly is also the model most commonly paired with overseeding because the three independently rotating tine sections follow uneven terrain well, maintaining consistent contact across bumpy ground.
The Agri-Fab 45-0299 spans 48 inches with 32 tines — tied with the Ohio Steel 48CP for the widest of the three reviewed models rather than ahead of it, and the 48CP fits 40 core points into that same width. Spreading 32 tines across 48 inches means lower tines-per-linear-inch than a narrower machine, so the Agri-Fab particularly benefits from crossing passes to compensate. Its seat-operated transport lever is a meaningful practical advantage here: raising and lowering the tines at the end of each pass without dismounting saves real time when you're making multiple passes across a large lawn.
Pass count when overseeding
If you're aerating as preparation for overseeding, err toward more passes rather than fewer. The mechanism of aeration overseeding is seed falling into plug holes and making direct contact with the mineral soil below — which is what produces the germination rates that make aerating before overseeding so effective. More holes means more seeds finding contact. Three passes before overseeding is a reasonable target on any lawn where results matter.
After your final pass, spread seed immediately while the plug holes are fresh and open. Waiting even a day allows surface drying to partially close the holes and reduces seed contact quality.
Frequently asked questions
How many passes should I make with a tow-behind aerator?
Two passes at 90 degrees is the standard starting point. A single pass typically produces 5–8 plugs per square foot. Iowa State Extension puts the target at 20–40 holes per square foot, so two passes is a realistic minimum rather than a finish — count holes in a square foot and keep making crossing passes until you are near the range. Heavily compacted clay may need four or more, spread across two sessions.
Can I aerate too much with a tow-behind?
Beyond four or five passes in a single session, you risk loosening the soil excessively. On wet or soft soil the bigger risk is tractor ruts — stop when wheels are noticeably sinking into the turf. For severely compacted lawns, spread passes across two sessions rather than doing them all at once.
Should the second pass be at 90 degrees?
Yes. Perpendicular passes punch new holes in the gaps between the first pass's plugs, effectively doubling coverage. A second pass in the same direction produces only marginal additional holes since the tines track nearly the same paths.
Does a second pass produce better plugs than the first?
Often yes. The first pass loosens the soil slightly, creating paths of reduced resistance. Second-pass plugs are frequently longer and cleaner than first-pass plugs on the same soil — which is one reason two passes at moderate weight outperforms one pass at maximum weight.
How do I know if I need more than two passes?
Count plug holes in a square foot of lawn after two passes. Under 8–10 holes per square foot means another pass will help. Also probe the soil with a screwdriver — if it still resists significantly after two passes, the soil needs more work.
Does soil type change how many passes I need?
Yes significantly. Sandy loam may be adequate after two passes. Heavy clay that's been compacted for years may need three to four passes across two sessions — two passes now, then two more in a few weeks after the first session's plug holes have begun to decompose and the soil has settled.