Clay soils and heavy traffic areas are particularly subject to compaction. If soil is trampled, especially when wet, compaction will likely occur. Compaction creates poor soil aeration, and restricts water and fertilizer movement through the soil, which causes thin, unhealthy grass.

A power driven aerator is the most effective method to relieve compaction. An additional benefit is the control of thatch, if it is present. Hollow tines pierce the soil to a depth of 7 to 10 centimetres (3-4") extracting soil cores which can either be removed or broken down and left on the soil surface. The openings allow water, air, and nutrients to reach turf roots.

Aeration should take place when the lawn is actively growing and when the soil is moist but not wet. Spring, after the lawn has been mowed two or three times, is the ideal time to perform this operation, with September as an alternate choice. It may be necessary to hire a landscaper or lawn care contractor who has the proper equipment. Some rental companies may also have appropriate units.

Generally, it is not necessary to aerate home lawns unless there is compaction or thatch problem. Compaction may be lessened by changing traffic patterns and refraining from the use of heavy lawn rollers, especially under wet conditions.

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