Steel In The Ground: The How and Why of Aerating
Updated: Sep 23
Steel in the Ground
At a sports turf conference in North Carolina one year, there was a panel of 4-5 MLB Head Groundskeepers talking about a variety of maintenance topics. Someone from the audience asked the question “how often do you aerate your fields?”. One of the panelists said, “I get steel in the ground as often as I can.”
That answer stuck with me my entire career and in this article, I will explain more about what he meant and how we can adapt it to our situations.
Let it Breathe
Most people have heard the term aerating and probably have done it themselves or have seen the process. It’s a fairly simple task, but it allows a cascading effect of positive benefits for our fields. While the soil receives most of the direct benefits, a healthy stand of grass is a by-product of those benefits. When I talk about aerating, I try to have the user focus on providing benefits to the soil, not just making their grass look better. This allows us to attack the cause of a lot of the problems, instead of focusing on the symptoms.
The process of aerating is poking holes through your grass and into the layer where the plant meets the soil. There are many different ways to aerate, and each one has a specific benefit, but they all accomplish two main things; allowing air, water, and nutrients to penetrate deeper into your soil and reducing compaction.
Roots and soil are the lifelines of grass. If we starve or suffocate them, the grass is directly impacted. By allowing air, water, and nutrients to reach a deeper level in the soil, it forces our roots to grow deeper and wider, allowing them easy uptake of the vital elements grass needs. Soil has billions of bacteria (mostly beneficial to the roots and plants) that produce waste through their natural lifecycle and use those elements. This waste after a period of time will turn into gas. Without aerating, this gas will aid in the suffocation of the root system. When we aerate a field, it not only allows the oxygen down to the roots but also allows the soil to exhale some of those harmful gases.
Athlete safety has become a much bigger concern over the past decade or so. This stems from brain trauma that has been spotlighted by professional athletes but has also made impacts at all levels. As sports fields get hundreds and thousands of athletes running and stomping on them, this compacts the soil underneath, which is amplified as fields are played on when wet, which is very common. After yearly use, and especially if the soil underneath has a lot of organic matter and heavy clay (which is also very common), this can make a field unsafe for the athletes by becoming too hard. Aerating mechanically reduces that compaction by removing a soil core and allowing more space for the soil to expand and “open up”.
A Paradox of Choice
Having too many options may seem like a good problem, but it can be a problem nonetheless. There are two main ways to aerate a field; core/hollow tines and solid tines. But within each of those choices, there are many more choices to make; width, length, style, compatibility, durability, etc. Any of these choices are beneficial to aerate with, but they all have specific functions that can improve, or reduce, the efficacy of your aerating.
The most common aerating is core/hollow tine aerating. This is when a hollow tine is inserted in the ground and removes a core of soil or “plug”. I have always happily referred to these as “poop pellets”! The main function behind this type of aerating is to amend your soil profile. It also reduces compaction and allows air to the soil, but I try to focus on amending the soil specifically when hollow tine aerating
The vast majority of fields I walk on need a significant amendment to their soil. They are usually native soil fields, heavy in clay and organic material. While that’s not intrinsically negative, there are plenty of benefits to organic material, but it can become a serious problem when there is too much in the soil and increased compaction. By core aerating, you can remove a small, but not insignificant amount of that old soil, discard the plugs, then top dress with sand or sandy loam material. This process of diluting the soil takes years to fully accomplish but is a cycle that will continue to provide long-term positive benefits (i.e. reducing compaction, allowing for better drainage and root growth, and a healthier grass).
The other type of aerating is solid tine. Instead of removing a core/”plug” from the ground, solid tines just poke holes. There isn’t one specific function I try to accomplish when solid tining. I use it for a variety of reasons. It helps reduce compaction, exchange of the gasses we talked about earlier, aids in drainage, and promotes a denser root system and field. Now comes the fun part, choosing which solid tine. There are needle tines, star tines, knife tines, spider tines, and so on, that you can choose from. If you get to the point of having trouble deciding which tine to use, that’s a great problem to have! Each of the solid tines will provide one benefit a little more than all the other ones. For example, if you use a star tine, you will be cutting more stolons/rhizomes thus improving the density of your grass. If you use a needle tine, you may not cut as many stolons/rhizomes, but you can usually go a little deeper in the soil to help with drainage and gas exchange. All of them will help reduce compaction, but compared to hollow tining, this is a short-term benefit.
Now that you may be overwhelmed with all of the choices you can make, let me try and make it a little easier. While getting “steel in the ground” is the most important idea when it comes to aerating, meaning there’s no right or wrong choice to make as long as you are getting something in the ground, there is an order of operations I think you should prioritize.
If you can only aerate one time per year, my strong suggestion is to core aerate, preferably in the spring or fall. This allows you to get the most bang for your buck. You can relieve compaction as well as start the process of amending your soil. If you can only aerate this one time, I would try to remove the cores and top dress after as well.
That is step number one. After you have your first core aeration done, you have more options for your second one. If you have the ability to aerate twice a year, I would still recommend core aerating both times as well as removing the cores and topdressing. Considering the labor and materials cost of this process, and if this presents a challenge for you, your second aeration can be any type of solid tining. This process still provides a great benefit, but with a fraction of the time and cost because there is no clean-up or topdressing needed.
The first aeration should be hollow tines with removing the cores and topdressing; ideally in the spring and fall. The second one can be replaced with a solid tining if time and budget are factors. Anything you are able to schedule after those two is icing on the cake and should most likely be done with a solid tine to reduce labor and material costs.
Outside of mowing and fertilizing your field, aerating is probably one of the most important maintenance practices for a sports field. Most problems on a field originate from issues in the soil and aerating allows you to start the process of fixing the core problem, instead of just managing the symptoms that problem is causing. While it does take a good amount of scheduling, labor, and possibly materials to aerate, the benefits heavily outweigh the costs.
Don’t overcomplicate the process. Try and follow some of the suggestions I’ve made here, but the main goal is to get a process in place and start getting steel in the ground.