Soils that are hard and compacted impede root growth, which prevents the grass from developing the deep root system that is essential to survive hot, dry periods.
Core aeration is the process of mechanically removing plugs of thatch and soil from the lawn.
Aeration opens the soil, helps reduce compaction, improves water infiltration, improves rooting, reduces thatch and acts in many other ways to improve the lawn and to reduce stress. Power raking is also an effective way to reduce thatch buildup, but it does not have the soil stress alleviation effects of core aeration. These techniques are labor intensive processes that require specialized equipment, but they may be necessary to maintain your lawn in top condition over an extended period of time. Core cultivation is not as effective as power raking in removing thatch debris, but serves more immediately to reduce soil compaction. Soil cores are either removed or allowed to stay in place after the cultivation process.