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Aeration of Lawns

Aeration of a lawn consists of extracting cores of soil from the lawn area. This is accomplished with a machine having hollow tines or spoons mounted on a disk or drum. When driven across the lawn, the machine extracts cores of soil 1/4 to 3/4 inch in diameter and 1 to 3 inches in depth. The two major reasons for aerating a home lawn are to help control thatch development and to help reduce soil compaction in the surface zone of the soil.

Thatch is a layer of organic matter that develops between the soil surface and the green grass leaves. Development of thatch greater than 1/2 inch thick can lead to greater drought, insect, and disease problems. As increasing numbers of lawns in North Dakota are being highly maintained by regular irrigation and fertilization, development of excessive thatch is becoming a common lawn problem.

Aerating a lawn helps control the development of thatch by increasing the activity of the soil microorganisms responsible for decomposing the thatch layer. The soil core which is brought to the surface in the process of aeration, gradually breaks down and filters down into the layer of thatch, resulting in a mixture of thatch and soil rather than the layer of organic matter associated with pure thatch. The mixture of soil and thatch retains more nutrients and water than a layer of pure thatch. Consequently soil microorganism activity and the rate of thatch decomposition increases.

The surface zone of many North Dakota lawn soils is excessively compacted. Because water infiltration into the soil is reduced when soil is compacted, the lawn area stays excessively wet for longer periods of time following rainfall or irrigation and more of the water runs off the surface. In addition, the growth of grass roots may be reduced by soil compaction due to less oxygen movement to the roots. Aeration of the lawn leaves open holes which gradually fill with uncompacted soil from break-down of the cores left on the surface and from soil sloughing off the edges of the hole. Following aeration of a lawn, water infiltration is higher, oxygen movement to the roots increases, and grass growth is stimulated.

The best time of year for lawn aeration is late summer between August 25 and September 20. At that time the lawn is generally coming out of a summer stress period and into a period of vigorous growth, thus the lawn will recover from the aeration quickly and will have a rather long period of good growing conditions. Weed competition will also be minimal during that period. The next best time for aeration is in the spring--generally early May, after the grass has begun active growth!

Be sure the machine you rent has hollow tines or spoons which bring the extracted soil core to the soil surface. Equipment having solid tines create a hole in the turf by compacting the soil and are not recommended.

If you have further questions, please contact your county office of the NDSU Extension Service.

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