Now is the time of year to aerate your lawn.
This is a mechanical process where pieces of your soil are removed by a machine called an Aerator. It helps to improve drainage, allows nutrients and water to reach the soil, and preps the soil for over seeding.
To rent an aerator costs about $60 or a half a day. Buying an aerator on how to aerate your lawn is not economical because it costs about $4000.
Some good aerators are the Ryan Lawnaire 28 and the Plugr PL850. These are good commercial machines.
When you aerate you will want to make sure the soil is wet the night before so the plugs come out more easily. You will want to mark sprinkler heads to make sure that you do not hit them with the machine.
To learn more you can visit How to Aerate Lawn.

