What is Compacted Soil?
Generally speaking, soils are made up of 50% solid ground and 50% pore space and soil compaction occurs when the pore space has been reduced. A reduction of even 10% will be enough to compromise the health of your lawn.
This reduction in pore space not only inhibits natural drainage of water but it also greatly reduces the supply of water, oxygen and nutrients to your turf and surrounding plants but also to vital microbes and creatures that live in the soil. Soil compaction will usually occur just a few millimetres under the surface; however this can extend up to 30cm in areas where heavy machinery/equipment has been used repeatedly in one area such as parking a car in the same spot.
Soil type also plays a variable role as sandy soils will compact less than clay soils and wet soils will compact faster and deeper than dry soils. Turf that is compacted will grow slower, be short and will eventually become thin allowing weeds, moss and algae to grow. It is good to remember that a healthy well managed lawn will be able to offer a degree of protection against soil compaction as a result of occasional human and animal footfall traffic and activities such as mowing as a healthy lawn will cushion the soil. However, over time these activities will cause compaction, so it is good practice to aerate your lawn as part of routine maintenance.
What can I do if I have compacted soil?
Compacted soil areas can be identified if your turf has started to thin out or if after heavy rain it pools and takes a day or two to drain away.
If your soil is compacted the good news is that it can be reversed relatively easily providing it is not too deep. The way in which to do this is by aerating the soil (punching holes in the turf) to create more pore space either by using a garden fork if the area isn’t too large or by using an aerator such as the Draper Rolling Lawn Aerator which will create 3.4cm deep holes. Alternatively, if the area of compaction is likely to be a little deeper than just under the surface (i.e. a grass path or area of lawn that is regularly walked over/compressed) you may be better with a manual aerator such as the Draper Lawn Aerator which will punch regular holes 1.2cm in diameter.
If the area of compaction is likely to be much deeper than the above two (for example the area has been used to regularly park a car on or is very heavily used) it may be a job for a professional using specialist equipment.
How often and when should you aerate?
If your soil was compacted it is best to aerate several times throughout the year rather than doing a lot all at once to restore it. The distance between holes should be 2.5cm to 5cm which will help to ensure an effective restoration.
It is best to aerate your lawn in the growing season from spring to autumn before any topdressing or lawn feed is applied. The reason for this is so that as the turf grows it has easier access to water, nutrients, oxygen as well as space to grow into. Although aerating can be done in the summer it is best to avoid very hot and dry periods of weather as your lawn may suffer from heat stress, but this can be avoided by watering afterwards.