Homeowners often overlook problems associated with soil compaction. Insects, diseases, nematodes, improper watering and/or a lack of fertilizer are often blamed for a lawn's decline when the real culprit is compaction. The problem starts when the top 4 inches of the soil become compressed; thus impeding the movement of air, water and nutrients to the grass roots. This stresses the grass, making it 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-aerated soils. Therefore, some lawns may require frequent aeration to aid in thatch control.
If soil is compacted, the solution is straightforward: aerate. 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 is 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 aerate in the fall or in the summer. Lawns composed of cool-season grasses such as Kentucky bluegrass and tall fescue are best aerated 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 grass recover. Warm-season grasses such as zoysia grass, centipede grass, carpet grass, St. Augustine grass and bermuda grass, on the other hand, are best aerated in summer after fertilization is in place and when they are actively growing (End of May thru Middle of August). 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 aerating a wet soil, as it will lead to more compaction. If the soil sticks to your shoes or if the core sample 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 aerate. If it is difficult to penetrate the soil with the screwdriver, then you may need to aerate. 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 bermuda grass and zoysia grass.