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Homeowners often overlook problems associated with soil compaction. Insects, diseases, nematodes, improper watering and a lack of fertilizer are often blamed for a lawns decline when the real culprit is compaction. The problem starts when the top 4 inches of the soil become compressed, impeding the movement of air, water and nutrients to the grass roots. This stresses the grass plants, making them less able to compete with weeds and slow to recuperate from injury. In time a compacted lawn needs renovation.
Compacted soil contributes to the accumulation of thatch because restricted oxygen levels in highly compacted soils impair the activity of earthworms and other thatch-decomposing organisms. Left unmanaged, thatch can lead to serious maintenance and pest problems. Thatch accumulates faster on compacted soils and heavy clay soils than on well-aerified soils. Therefore, some lawns may require frequent aerification to aid in thatch control.
If soil is compacted, the solution is straightforward: aerify. The practice of physically removing cores of soil and leaving holes or cavities in the lawn is defined as core aeration or aerification.
Benefits of Core Aeration
- Loosens compacted soil and increases the availability of water and nutrients.
- Enhances oxygen levels in the soil, stimulating root growth and enhancing the activity of thatch-decomposing organisms.
- While removing cores of soil, the spoons or tines also sever roots, rhizomes and stolons. Grass plants are stimulated to produce new shoots and roots that “fill up” the holes in the lawn and increase the density of the turf.
- Reduces water runoff.
- Increases the lawn’s drought tolerance and improves its overall health.
The type of grass will determine whether to aerify in the fall or in the summer. Lawns composed of cool-season grasses such as Kentucky bluegrass and tall fescue are best aerified in the fall, when there is less heat stress and danger of invasion by weedy annuals. Allow at least four weeks of good growing weather to help the plants recover. Warm-season grasses such as zoysiagrass, centipedegrass, carpetgrass, St. Augustinegrass and bermudagrass, on the other hand, are best aerified in late spring and summer, when they are actively growing. With either type of grass, choose a day when temperatures are mild and soil is moderately moist, which makes the soil easier to penetrate. Avoid aerifying a wet soil, as it is messy and leads to further compaction of the soil as well. If the soil sticks to your shoes or if the core sample you take sticks to your probe, you should wait until it dries out some before starting the job.
Aerification of home lawns corrects soil problems but generally is not a routine practice. The best answer to the question, “How often should I aerify?” is, “As often as needed.” One way to determine if aeration is needed is by scouting the lawn. Take a screwdriver and probe the soil. If the screwdriver penetrates the soil with little resistance, then you probably don’t need to aerify. If it is difficult to penetrate the soil with the screwdriver, then you may need to aerify. Make sure the soil is moist when testing the areas since dry soil can also be more difficult to penetrate.
Turfgrass in high traffic areas may need aerification more often than the rest of the lawn. Turfgrasses with low traffic tolerance such as centipedegrass and St. Augustinegrass may need aerifying more often than turfgrasses with good traffic tolerance, such as bermudagrass and zoysiagrass. These high traffic areas can usually be done by “hand” as described in the next section.