Soil compaction occurs when the soil has smaller pores or fewer spaces that can contain air and water needed for growth. It leads to a situation where the soil is less permeable, can store less water and where it is harder for roots to penetrate. Soil compaction also makes it difficult for fertiliser and its required nutrients to get to where they need to be.
High traffic areas such as the backyard cricket pitch, the path to the clothesline, the dog’s favourite route the chase the postman and the site the car is parked on will suffer the most from soil compaction.
Compaction occurs more easily when soil is wet since the water acts as a lubricant allowing the particles of the soil to be rearranged, filling in the required spaces. It is most prevalent in soils with a high percentage of clay. If left unattended dead patches will eventuate in the lawn and weeds will move in where there is no longer any competition. Because the plants may be forced to grow along the top of the lawn rather than penetrating further down thatching is another potential problem.
To check to see whether or not your soil is compacted push a garden fork or screwdriver into the lawn. If the fork struggles to get into the soil at least half way up the tines then your soil is compacted.
What to do now. To rid your lawn of soil compaction you will need to aerate the soil. Aeration basically means ‘supplying with air’. This process will open up larger spaces within the soil and therefore allow oxygen, water, fertiliser to penetrate the soil as well as allowing for movement of all those fantastic earthworms that make the soil all the richer. Give the area a good watering the day before aeration to make the process that much easier.
The size of the area requiring aeration will determine the best tools to complete the job. Smaller areas can be dealt with manually with either a garden fork or aerating sandals. Larger areas will be best handled by using petrol aerators that can be hired from your local equipment hire centre for around $70 per day. An aerator will pull small plugs of soil out that are about the size of your finger and deposit them on the top of the lawn. They can be left there since they will break down in about two weeks.
To alleviate the problem of soil compaction annual aeration of the lawn is highly recommended although in very high traffic areas it may be required more often.