Lawn compaction is a common problem; it is caused by wear and tear and heavy traffic. For example if you like your backyard cricket, around the batting crease or bowlers run-up you will find the soil can get compacted, or if you are walking back and forward to the washing line. It is easy to check for and it is pretty easy to fix.
To test if you have a compacted lawn, simply push a garden fork or screwdriver into the ground. In a good lawn, the tines of the fork should easily go down halfway or more, if they don’t the chances are the lawn is compacted and it needs some fixing.
You can aerate compacted lawns with a garden fork or power aerator or coring machines. You can hire petrol driven lawn aerators from equipment rental companies.
You can also apply gypsum to compacted lawns at the rate of about 1 kilo per square metre. Once the lawn is aerated it will grow strongly again and outcompete bindii and other nasty broadleaf weeds.