Soil Compaction in the Lawn

What is soil compaction

Most lawns will have or will experience the affects of soil compaction during their lifetime. All soils require a certain percentage of air in order to support a healthy lawn.

Soil compaction occurs when the majority of the air is squeezed out of the soil by excess traffic. The traffic can include garden machinery such as mowers, vehicles like cars or people using the lawn.

The more traffic the lawn receives the greater the compaction, is likely to be and the soil particles are pushed together reducing the amount of pore space available for air.

Generally speaking soils with a high content of clay are more prone to compaction than sandy soils. This is because clay has a smaller particle size than sand and the air is squeezed out more easily, especially when the soil is wet.

When soils become compacted the following happens:

• Air space is reduced.
• Root growth is restricted and shallow rooted weed grasses invade at the expense of the deeper rooted desirable grasses.
• Drainage is impeded and water logging and puddling become the norm.
• As root growth is shallow, then the lawn becomes very susceptible to drought conditions.
• The lawn is open to attack from pests such as broad-leaved weeds and disease, as growth is likely to be thin and the grass plant will be unhealthy.
• As the grass becomes stressed due to soil compaction, nutrient uptake is generally poorer than on healthy turf.
• The thatch layer will build up quicker, as the micro organisms, which breakdown the thatch in the lawn, require air to survive.

All of the above symptoms and conditions, result in a weak lawn and something must be done to restore the lawn to its former health.
A good way to test if you have soil compaction is to push a garden fork or soil profiler into the lawn. If there is too much resistance, you may have compaction and steps will have to be taken to address the issue.

Controlling soil compaction

Compaction can be relieved using some form of lawn aeration. In fact regular aeration should be carried out at least once a year on most lawns. Clay soils may need additional aeration they are more at risk to compaction than light sandy soils.

There is a variety of aeration equipment and tools available to the amateur gardener to combat soil compaction. These include hand forks, hand corers and powered spikers and corers. For more information on these you can visit our lawn aeration and lawn aerators page.

Once you have successfully controlled compaction it is important to prevent it from returning by aerating the lawn on a regular basis. Aerate at least once a year, twice if you soil is prone to soil compaction.

Aeration is regularly carried out on sports turf such as football fields, golf and bowling greens. Turf professionals know the ills of soil compaction and do something about it prior to it becoming a problem. Sports turf receives a large amount of traffic and regular routine aeration is required to prevent soil compaction.

Turf professionals have a variety aerators at their disposal. These aerators include verti-drain machines which heave shatter the soil, hollow tine machines which remove cores of thatch and soil, shallow spikers, air injection aerators and more.

Each machine has its own benefits and uses in the battle against compaction. Another important factor is that turf professionals vary the depth of aeration to stop a pan forming in the soil.