Soil compaction & aeration

Compaction is the reduction of soil pore space. Soils are generally 50% pore space and 50% solid. The pore space is needed to conduct water and oxygen to your turf and many thousands of other plants, microbes and animals that live in the soil. 

Keep reading to learn more about compaction and the process of aeration.

General information

  1. Is your turf thinning out?
  2. Does water stay on the turf surface for a day or two after heavy rain?

If your turf is not growing well and you answer yes to the above questions, the soil under your turf may be compacted.

As stated above, compaction is the reduction of soil pore space. 

When the pore space is reduced by even 10%, your turf will suffer. The turf will grow slowly and it will be short.

Eventually it will become thin, thus allowing weeds, algae or moss to grow. The compaction generally occurs within a few millimetres under the turf.

However, if heavy equipment is used the compaction can reach a depth of 300mm or more.

Info centre - flooded lawn

However, if heavy equipment is used the compaction can reach a depth of 300mm or more. For example, the repeated parking of cars on turf will compact the soil. Turf soils that are compressed when wet, compact deeper and faster than dry soils. Clay soils compact more than sandy soils. Remember, healthy turf will cushion the soil from occasional activities such as running, mowing the lawn and animal traffic, but any repeated activity will eventually cause compaction.

How to relieve compaction

Compaction can be reversed, and if it is shallow it is not that difficult to do. Simply put, you must create more pore space under the turf. This process is called aeration. To do this, holes are made in the turf. The holes for shallow compaction need only be 75 to 100mm deep, but the holes for deep compaction might need to be greater than 300mm deep. To relieve compaction in small areas of turf, you can use a garden fork or hand operated spikers. These are tools that, when pushed into the ground, will create holes. These can be purchased at local garden centres. There are machines that can do this as well, but these are better left to a professional to operate.

Dealing with deeper compaction

If your lawn suffers from particularly poor drainage and heavy compaction it could be that the standard aeration technique may not be enough. In this situation you could consider a more intensive course of action known as hollow tining or hollow coring.

Hollow tining goes further than simply spiking your lawn. It removes cores of around 13-16mm diameter, dependent on machine design. This lets more air into the topsoil, allowing it to breath, aiding the drying process and more importantly letting topsoil particles move apart.

As with aeration, after hollow tining and once you have picked up the cores, you can apply a topdressing of your choice dependent on what your lawn needs. If you are on a clay soil you could use a course sand or horticultural grit, brushed into the lawn, which will help improve overall drainage by keeping the soil from closing up. This helps prevent build-up of moss and maintains a better pathway for air to penetrate to the roots. 

Note: Your new Rolawn turf does not require aeration.

How much should you aerate your turf?

It is unlikely that you will aerate your turf too much. However, it is better to repeat the process several times a year if your soil is compacted, rather than do a lot all at once. If the holes that you make in the turf are about 25-50mm apart, you have done a good job. Repeat that several times a year and your turf should improve. As the turf grows, it too will reduce soil compaction as its roots push soil particles apart. If you see signs of earthworm activity in your lawn this will help, as earthworms naturally aerate the soil by creating small pockets of space as they move through the soil.

When should you aerate your turf?

It is best to aerate your turf when it is growing, especially before applying a lawn food or topdressing. This allows the turf to grow into the aeration holes where there is plenty of water, oxygen and space. Caution should be taken if aerating when it is hot and dry. Open holes in your turf when it is hot and dry could cause the turf to suffer from drought and heat stress. To avoid this, water the turf after you aerate (see Watering your turf and soil drainage).


Even healthy lawns can suffer from compaction, but it can be relieved through aeration.

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