Walking on your lawn compacts the soil which in turn grows poor lawn grass. The solution is simple. Aerate your lawn. Aeration is claimed to loosen the soil, reduce compaction, reduce thatch and grow better grass. But is this really true?
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Types of Lawn Aeration
There are several kinds of aeration including core aeration, spike aeration and liquid aeration.
Core Aeration
This type of aeration uses a machine that pulls a plug of grass and soil right out of the ground. When the process is complete, the lawn is full of small holes and the surface of the grass is littered with small soil plugs that looks as if it was visited by a flock of geese.
Many gardeners do not like this kind of aeration because it looks messy for a few days. However, it is the best option.
There is a debate about removing the plugs or leaving them on the lawn, but the best approach is to just leave them. They fall apart in a couple of days and the extra soil on top of thatch helps to reduce the thatch.
Spike Aeration
With spike aeration a pin, spike or nail is pushed into the soil, leaving a small hole. This can be done with an automated machine, a manual fork-like device and some gardeners try to use special spiked shoes. The shoes are a terrible idea and might break your ankle.
Driving a spike into soil does create a hole, but it also compacts the soil around the hole. Spike aeration does not aerate soil, reduce compaction or have any effect on thatch.
Liquid Aeration
The attraction to liquid aeration products is the convenience factor and the fact that you can do it yourself. Connect a bottle to the end of your hose and water the lawn. The chemicals in the bottle soak into soil and reduce compaction – or so it’s claimed.
The content of these products is not usually made public but the main ingredients can be a combination of a surfactant, humic acid and seaweed extract.
Surfactants are a type of soap that make it easier for the product to soak into the soil. There are all kinds of mythical claims for humic acid, so why not claim they reduce compaction.
The Colorado Extension office says, “It is simply wishful thinking to believe that a highly diluted solution of either of these (surfactant or humic acid) applied to a compacted soil will in any way affect soil bulk density (i.e. compaction). There is no indication that ANY of these products has ever been scientifically evaluated for effectiveness.”
Other reliable sources as well as research reach the same conclusion. Liquid aeration does not work.
Do Lawns Have Compacted Soil?
I asked Dr. Sara Stricker, Communications and Outreach Coordinator, Turfgrass Institute, University of Guelph about core aeration and she pointed out that lawns may not have a compaction problem.
For example, lawns built on native clay soil in Southern Ontario that have been in place for more than 10 years and have low foot traffic (most lawns) don’t have significant compaction.
Compacted soil can be a concern in new developments where heavy machinery has compacted the soil during construction, but this compaction naturally corrects over 5 years.
Older lawns probably don’t have a compaction problem to fix. New homes have compacted soil, but if left alone, nature reduces compaction over time. Mechanical aeration may help to speed up the process.
Do Lawns Have a Thatch Problem?
Lots of people assume that they have a thatch problem. Around here, gardeners are outside first thing in spring raking out their perceived problem. It turns out that many lawns don’t have a thatch problem and this early raking actually harms the lawn.
A thatch layer of 1/2″ (1.3 cm) or less is not a problem. In fact a thin thatch layer is good for turf. It holds in moisture, cools the roots and slowly decomposes to feed the grass. A thicker layer is a problem because it can reduce water infiltration when it rains.
For a more detailed discussion of thatch see Dethatching Lawn Thatch.
DIY Infiltration Test
Do you have an infiltration problem that could be caused by thatch or compaction? It is easy to test this for yourself by following this simple DIY infiltration test.
Does Core Aeration Reduce Compaction?
The technique will not reduce compaction if there is no compaction, as in the case for older homes, or lawns with little foot traffic. But what about other cases?
Given all the lawns we have and the fact that core aeration is frequently recommended, you would think that there has been a lot of testing for it. If there is, I couldn’t find it. Here is the science I did find find.
On a highly disturbed and compacted site, plant growth was not improved with core aeration.
On sand-based putting greens treatments with and without core aeration had similar soil organic matter content, root weight density, and soil bulk density (i.e. degree of compaction).
In another study, repetitive overseeding combined with core aeration was used to increase the thickness of lawns. It was concluded that, “while core aeration can be a valuable practice, under the conditions of heavy rainfall, plots seeded multiple times with perennial ryegrass performed better without aeration, while aeration was neither a benefit nor a detriment in tall fescue plots”.
Testing zoysia grass in non-sandy soil found that aerification did not significantly improve turfgrass quality. The best approach for dealing with thatch and increasing quality was to apply nitrogen alone.
Tests on the main lawn at the Olympic Stadium in Rades, Tunisia using two different densities of core aeration (# of holes per unit area) found that initially the aeration work unpacked the soil. However, this situation lasted only twenty days and then the soil began to compact again, which negatively affected the fresh and dry matter yield, and the root length. A higher core density did give better results.
Tests with Bermuda grass on clay soil found that, “core aeration applied once or twice per year caused a loss of stand density (i.e. produced thinner grass) and did not reduce thatch accumulation regardless of whether cores were removed or returned”.
I could not find a single study that showed core aeration reduced compaction on home lawns. That is quite surprising since most of the on-line advice for maintaining a lawn promotes the idea.
Other Benefits of Core Aeration
This technique has also been recommended to solve other problems including the following:
- Mix new soil with native soil
- Pest Control
- Incorporate amendments
- Help with overseeding
Mix New Soil with Native Soil
New lawns are usually installed with a very thin layer of top soil on top of the native soil, which is usually only subsoil. This creates two layers of very different soil which can lead to problems with water moving from one to the other. Aeration can help mix these two layers.
Pest Control
Hairy chinch bug, Blissus leucopterus hirlus, exists in larger numbers under lawns that have thicker thatch. Reducing thatch with aeration should also help reduce this pest.
While some studies have reported that core aeration can be used to control white grubs, it had no impact in other studies.
Incorporate Amendments
The addition of lime to acidic soil is a common practice for increasing pH. The effectiveness of the lime is increased when it is combined with core aeration.
Help With Overseeding
A common practice is to aerate before overseeding a lawn. It is believed that this provides better contact between seed and soil, which leads to higher germination. It might be better to save the cost of aeration and use more seed?
Does Core Aeration Reduce Thatch?
There is little research on this, but there is some evidence that it may work, although the research mentioned above was not very positive. Leaving plugs on the ground adds soil over the thatch and may speed up its decomposition.
Experts agree that it is not the best technique for this job. If you have thatch, use a dethatching machine which works much better. “Dethatching is the removal of thatch that has accumulated in the turf and is a very aggressive procedure that will leave piles of debris on the lawn that will then need to be raked and removed”.
Should Homeowners Aerate Lawns
Except for some of the special cases mentioned above, lawn aeration is not supported by science. Most home lawns will not have enough compaction to benefit, and even when they do have high compaction the technique may have little effect or its’ effects are short term.
If that is true, why do so many government sites promote the technique?
I don’t have a good answer except to suggest that it is just another myth that is heavily promoted. If you find some science to support core aeration, please add them to the comments below.
Dr. Sara Stricker commented that even if it does not help, it won’t harm your lawn.
I found that when I cut lawn without grassbox and all grasscuts are left on the lawn, at night I can find these big fat >20cm earthworms on it. I believe they do the work, but it is better to leave small grass clippings.
The plugs are good examples of products made without checking if there is a need for it. Often people read articles and get temted to buy products they dont need.
I received a “duplicate comment. Looks like you’ve already said that,” instead of “your post is approved.
From now on, I’ll be shouting, “COMPOST!”
I’ve grown tired of all these “new methods.”
Yes, I do core aerate – about once every 5 to 6 years.
I Compost my lawn, growing beds, every year, sometimes Twice!
There is only One effective method to keep you soil loose and friable and nutritious.
Worms!
Compost removes the thatch. Compost is filled with Worms. Compost holds moisture. Worms surface through the Compost and them carry the Compost ever deeper!
The Real Performer is Compost!
Ranted comment over. All I hope is that this helps. That’s all I want for Every Person!