Aerification, or core cultivation is a service which pulls cores of soil up from an established turf area with minimal disturbance to the turf. The goal of this is to increase the soil's aeration, which is the amount of available oxygen in the soil.
Core cultivation is often used in conjunction with other services, such as seeding and top dressing. Coring depth and cores per square foot are the two measures of a good core aerification.
Timing: For warm season turf, an aerification service should be performed during periods of peak growth, such as late April through June. Late summer aerifications are sometimes necessary if foot traffic or stress create the need. For cool season turf, aerification is done in Late-Summer to Early Fall and is virtually always done with a seeding, to improve turf density.