University of Maryland Extension

Lawn Aeration

aerated lawn

Mechanical aeration alleviates soil compaction in established turf, encourages root growth by increasing oxygen to roots, and allows seed, lime, and fertilizer to enter into the soil.

  • Compaction occurs primarily in the soil surface. A compacted layer as thin as one-fourth to one-half an inch can greatly impede water infiltration and gas exchange between soil and atmosphere.
  • Aerating machines should remove plugs of soil from the turf, creating a system of large pores by which moisture and plant nutrients can be taken into the soil. They are referred to as core aerators. Core aerators pull plugs about ½- to ¾-inch in diameter, 2 to 4 inches deep, and about 2 to 6 inches apart. Equipment having solid tines or spikes should not be mistaken for aerating equipment. These types of machines actually increase soil compaction by compressing the soil into a denser mass.

plugs of soil laying on grass
Soil plugs created by core aerator

  • Fall is the best time to aerate cool-season lawns, and June through July is the recommended time to aerate warm-season lawns. Never aerate when a lawn is dormant. A general rule is to aerate only when desirable grasses are growing vigorously.
  • Soil should be moist, but not wet, before aerating. Irrigate the lawn prior to aerating if the soil is dry.
  • Aeration can be done before overseeding. This procedure makes holes for the seed to fall into, therefore increasing seed-to-soil contact. 
  • Core aeration should be performed every one to two years on lawns that receive heavy foot traffic. Otherwise, aerating every two to four years on home lawns is sufficient.
  • Soil plugs can be left on the surface of the lawn. They will decompose in a couple of weeks.

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