Is Lawn Core Aeration Worth It?

What is Aeration/Aerifying?

As a Golf Course Superintendent, I have a tiny issue with the term Aeration. Not in a negative sense, but in the misunderstanding of the use of the word when referring to grass. Aeration is the act of introducing air into something by an act. Many feel that this should only be referring to a water fountain or diffuser in a pond. They are wrong! Core aeration is the introduction of air into the soil by mechanical means. Consequently, the term is right, if you use it, keep doing so!

With that out of the way what is it that all these landscape companies are doing and forcing into their programs spring and fall? Is it the right process? Is it necessary? We all see them doing it each year, so the general consensus is that it must be beneficial. Well, it’s true to a degree.

What is the Process?

Core aeriation is the process of removing a soil plug from your lawn with the depth being around 2 to 3 inches. The coring tool is called a tine, is hollow and has a diameter of between 1/4 to 1 inch. They are set on a machine that can vary in tine spacing with a closer spacing being more aggressive and able to remove more soil with one pass. Spacings can range in a row from 2 to 4 inches and on the column 2 to 8 inches.

What Does it Do?

Thatch removal, compaction reduction and organic matter (humis) removal are the three functions for core aeriation. Thatch is that spongy organic part just beneath the grass stem and into the soil surface, It consists of decaying organic matter, grass clippings and stems of the grass. Too much or excessive thatch leads to an increase in disease and insect occurrence, and it also reduces the effects of fungicide applications. Humis is broken down organic matter that is in a gel like state and binds soil particles together and can make your lawn hydrophobic (water repellent). Functionally excessive thatch creates a spongy feeling layer on the soil surface that may feel uneven to walk on. Annual thatch accumulation can vary depending on region but 5% to 15 % of surface area measured by weight is standard. So, it’s important to at least remove enough thatch annually just to stay the same. Any thatch removal processes therefore need to be calculated and should be asked if you have a company doing it.

Compaction is soil that has increased in bulk density over time to a point where it can eventually have a significant negative impact on turf health by being too dense for roots to push into. Soil air space is reduced and soil water holding capacity is adversely affected. Compaction tends to happen next to and in high traffic areas like walkways, paths, travel routes, goal posts and in and around play areas like swings etc. Certain weeds can also help you identify compaction as their niche is growing in compacted soils. Greater plantain, annual bluegrass, chickweed and spurge are the main ones. Grass becomes weak and thin in compacted soils.

How Much Does Core Aerating Remove?

When you get a soil test taken, try to find a soil testing kit that will measure soil organic matter %. This should be your baseline and the following year at the same time you can get another test and see what the difference is. The percentage difference is the % that you need to remove to keep the status quo.

There is an easy calculation for this and is:

An example of a common core aerifier aeriation pattern would be 4″ x 7″ with a tine size of 3/4″. The calculation for percentage soil removed is therefore:

Now we’ve established that with the average lawn core aerator we remove 1.6% surface area from one pass of the machine. In order to get over the minimum accumulation we need to do four passes. That being said how many times have you seen the plugs get picked up? If your answer is none then organic matter stays the same and there is no purpose in core aerifying. The only benefit you’re getting now is a core removal which will reduce compaction.

So, before you pay your landscaper or even let them start aerifying, ask 2 questions.

What’s the tine spacing? Are you going to pick up the plugs?

A Modern Method

Aerifying is undoubtedly an important cultural practice and should routinely be carried out. You have to keep the soil balanced with air and capillary spaces, allow gases to be exchanged, provide suitable rooting conditions and you have to manage thatch. To me pulling a core is an ineffective method for the home lawn though because it’s not removing enough thatch (if plugs are removed) and it’s not relieving compacting enough. So, what should you do?

Solid tining, verticutting and topdressing should be routinely carried out. These are a better approach as it helps fracture the soil, levels the grass surface and removes/dilutes the thatch percentage.

Solid Tining

Solid tining is self-explanatory and creates voids or deep slits in the soil similar to core tining but without the core. This creates a space where roots can grow into, the same as a coring tine. Compaction reduction is achieved by loosening up the soil from the impact and movement of the tine. This allows the soil to reset back to a less dense form before compaction started.

Coring machines can have their tines changed out to be solid but a pull behind roller with solid tines or spikes on it is great for the homeowner and only cost about $200. Put weights on it like cinder blocks to force the tines into the ground and you are good to go. Solid tining when the soil is moist is a better choice as tines will penetrate easier. Hand tining small patches like a walkway can also be done either with a pitchfork or small tining tool for about $75.

Scarifying

Scarifying is a series of vertical blades mounted on a horizontal shaft. The shaft rotates and slices into the turf canopy, removing decaying thatch and cutting any grass blades that are laying horizontally. The machine can be set to a variety of depths and should be done after solid tining.

It best to set it so you get a little bit of dirt when operating. Not too much as that would be too low. Thatch is in the top 1/2 inch of the soil surface, so that’s where you want to be, although caution should be taken when first operating this machine and the depth should be raised up until you get a feel for where the correct position should be.

Top-dressing

Scarifying removes a massive amount of thatch at one time, and you might be shocked at first. This process should be done when you know the grass has a good 3-week recovery time ahead of it before cold weather sets in.

Compared to core tining, the surface area affected by a scarifying machine set with blades at 0.5″ apart is 15% and set at 1″ apart it is 8%. This is a significant difference from 1.6% from coring and is a very effective method at removing thatch. It will also help level your lawn and will aid in reducing the bunching visibility of some tall fescue grasses. Frequent scarifying can be made throughout the growing season until you reach an acceptable thatch level and smoothness that you desire.

Lastly and this is a recommendation only if you want to put in the effort and that is to level your lawn through top-dressing sand or loamy soil. This process would be done after scarifying and is another way of reducing organic matter by diluting the percentage of thatch by the addition of sand. Once the sand is spread across your lawn, level it into your lawn to fill in the low points. Do not use a brush at this point, instead see if you can locate a pallet or a tool called a level lawn. With the pallet, turn it upside down and put some weight on it, attach it to the back of your tractor with rope and tow it around your lawn in circles until it is levelled into your lawn.

All of these processes can be done frequently until you get to a stage where you are happy with the condition of your lawn. By carrying out these practices you are being more efficient and effective with your time whilst providing a beneficial environment for your lawn.