Soil compaction and tyre pressure

Heavy machinery compacts soil. Compacted soil has fewer pores, poorer drainage and aeration, and roots struggle to grow, which can reduce yields for years. Topsoil compaction can largely be loosened by tillage, frost and biology. Compaction in the subsoil, below working depth, can last for decades. That is why it pays to understand how tyre pressure and load act.

Two things drive compaction

Lower inflation pressure gives a bigger footprint and lower surface stress. A heavy wheel still gives high stress deep down whatever the pressure, so protecting the subsoil also means limiting wheel load.

Guide values

A widely used guide value from Swedish research (SLU, Håkansson) is that soil stress at 50 cm depth should not exceed about 50 kPa in moist soil. The app uses these indicative limits for moist soil:

How the app calculates

1. Contact area = load ÷ mean contact pressure, with mean contact pressure taken as about 1.1 × inflation pressure, limited by the tyre's width and diameter.
2. Stress with depth is calculated with the Söhne/Fröhlich method for a circular load, with concentration factor 4, 5 or 6 for light, medium or clay soil.
3. The results at 30 and 50 cm are compared with the limits above.

Worked example: contact area

A rear tyre carries 3,889 kg, about 38.2 kN. The load comes from the invented implement example in the axle load guide.

At 1.0 bar the load is spread over roughly 60 % more area than at 1.6 bar. Michelin's table allows 650/65R42 Multibib to carry 3,889 kg at 1.0 bar at 10 km/h, so the lower pressure is permitted in the field. See tractor tyre pressure.

Practical ways to reduce compaction

• Lower field pressure to the minimum the table allows for load and speed, and raise it before road work.
• Larger, wider or IF/VF tyres carry the load at lower pressure. Check lead, see changing tyre size.
• Dual wheels share the load and lower surface stress, though the total load still acts at depth.
• Avoid unnecessary ballast.
• Stay off wet soil where possible, because compaction risk rises sharply with moisture.
• Use fixed traffic lanes, and keep loaded trailers on headlands and tracks.
• Reduce wheel slip, which damages surface structure and wastes fuel.

Limitations

The model is an estimate for comparing options, such as two tyres, two pressures, or with and without ballast. Real soil stress depends on soil type, moisture, previous compaction, tyre construction and the number of passes.

Signs of compaction in the field

• Water standing in wheelings and on headlands after rain.
• Uneven emergence and poorer crops in wheelings and on headlands.
• Roots turning sideways at a certain depth, often below working depth (plough pan).
• Dense, sharp-edged clods and few earthworm channels when you dig.

A simple spade test or soil probe in and outside wheelings tells you a lot. Compare the same soil at the same moisture.

Step by step: plan for less compaction

1. Work out wheel loads for the heaviest combinations, for example tractor with plough or loaded trailer. See axle load.
2. Look up the lowest permitted field pressure for each tyre in the manufacturer's table.
3. Compare contact area and stress at depth for the options in Marktryck.
4. Prioritise where wheel loads are highest, because that is where the subsoil is at risk.
5. Plan the heaviest operations for when the soil is as dry as possible.

Example: standard or VF tyre for the same load

Vredestein's databook for 650/65R42, with 4,500 kg per tyre at 40 km/h:

The VF tyre carries the same load at 0.6 bar less. With the app's model (mean contact pressure ≈ 1.1 × inflation) that is about 176 versus 110 kPa in the footprint, roughly 37 % lower surface stress, assuming the area is not limited by tyre dimensions. Wheel load is unchanged, so the effect at depth is smaller. See IF and VF tyres.

Related questions

What tyre pressure reduces compaction most?

The lowest pressure the manufacturer's table permits for your load and field speed. Going lower is not permitted and can damage the tyre.

Does lower pressure help on headlands?

Headlands are compacted most because they get the most passes. Lower pressure helps at the surface, but lower loads and fewer passes help most.

How deep does a tractor compact the soil?

It depends on wheel load, pressure and moisture. Heavy wheels can cause noticeable stress below 50 cm, which is why there is a subsoil guide value.

Are tracks better than tyres for compaction?

Tracks have a large footprint, but stress under them is unevenly distributed, and comparisons depend on machine and conditions. The app only calculates for wheels.

Seasonal tips

• Spring: soil is often moist and most vulnerable. Wait until it carries, and use field pressures.
• Slurry and manure spreading: heavy spreaders and trailers often have high wheel loads. Check their tyres and pressures too.
• Harvest: plan routes for loaded trailers along the edges and use the same tracks.
• Autumn: a wet autumn means high subsoil risk. Limit wheel loads.

Comparison: lowest pressure for the same load

How much the tyre choice changes pressure, and therefore topsoil stress. Front tyre example:

Values are the lowest pressure in each table that carries the load. Some tables start at a minimum pressure at 40 km/h, which also affects the result.

Checklist: less compaction through the season

1. Calculate wheel loads for the heaviest combinations, see axle load and implements.
2. Read the field pressure from the table and lower pressure when entering the field.
3. Raise pressure again before road work.
4. Avoid driving on wet soil when possible.
5. Use the same tracks and plan headlands and exits.
6. Compare in Marktryck what lower pressure or another tyre gives.

Troubleshooting: signs of compacted soil

• Water standing in wheel tracks and on headlands.
• Poorer emergence and growth in wheelings.
• Dense, angular aggregates in a spade test, and roots turning sideways.
• Higher draft needed for cultivation on the same field.

How to do it in the app

Open Marktryck (soil pressure), pick a tyre and enter load and inflation pressure. The app shows the estimated contact area and stress at 30 and 50 cm against the risk limits. Try the same load at two pressures or with two tyres side by side.

Frequently asked questions

Does low tyre pressure reduce soil compaction?

Yes, in the topsoil: lower pressure gives a bigger footprint and lower surface stress. Subsoil compaction is driven mainly by wheel load.

What is the guide value for subsoil stress?

A widely used guide value is about 50 kPa at 50 cm depth in moist soil (SLU/Håkansson).

Do dual wheels help against compaction?

They reduce surface stress by spreading the load over more tyres, but the total load still acts at depth.

How much lower pressure does a VF tyre allow?

In Vredestein's databook the Traxion Optimall VF 650/65R42 carries 4,500 kg at 1.0 bar at 40 km/h, while the standard Traxion 65 needs 1.6 bar.

Is low pressure or low weight better against subsoil compaction?

Low wheel load. Low pressure mainly protects the topsoil.

Last updated 2026-10-15. General information. See disclaimer.