How often to aerate a lawn?
Doing lawn aeration on a yearly basis will help with most lawns. Generally however, when people ask how often they need to aerate their lawn, they are looking for a minimum. Most of the other lawn experts I have talked to recommend aerating once every 3 years. If you have the following you should definitely consider aerating your lawn every year if not twice a year:
Your lawn is on hilly or mountainous terrain. For some reason, this type of lawns always get harder, in addition, because they are on hills, the water is more likely to runoff. Aerating on a regular basis will help the water to better soak into the soil.
If you have clay in your soil, you should definately aerate once a year. During the summer months, this clay turns very hard, making it very difficult for water to be absorbed. If you aerate the lawn before the soil gets hard, as it hardens and expands the hole made by a core aerator will be able to absorb some of the expansion thus preventing compaction.
Another reason to aerate more often is if you have a lot of traffic on your lawn.
Often, I have noticed that people who have pets, or more active children tend to have more compacted lawns. Full size dogs and child day care centers create the most compaction. If you run a day care center you should definitely have your yard aerated twice per year. In addition, I have also noticed that tree roots under the soil can also cause compaction, this is because year round, but especially in the summer, the tree's root system can actually pull the water out of the lawn and these roots also expand as they grow. Both of these things also have an effect on hardening soils.