The great nemesis to lawns is clay soil, but unfortunately, most homeowners don’t have any control over the soil of their home until after the lawn has been established. This is because contractors dig up clay soil when setting the home’s foundation, or digging the basement, and that clay gets scattered in with the good topsoil.
Fortunately, clay soil can be corrected, but it takes time and patience. You will need to aerate your lawn to allow water and nutrients to penetrate the soil and, in some cases, add organic materials specific to your lawn’s needs through a method called top dressing.
Clay can actually be good for your soil and your lawn. Its ability to hold water and nutrients is needed when it is in balance with other properties of your soil. Reducing clay in an established lawn can take years, but it can be done.
Reduce Clay in Your Lawn the Right Way
Reducing clay in your lawn doesn’t mean removing the clay, as much as balancing it with the types of soil and materials that your lawn needs.
Clay can become a problem because it is made up of tiny particles that cling tightly together. This means that clay holds on to water and nutrients creating a soggy, soppy soil with poor drainage when it rains, and a hard-as-concrete soil that is impossible to work with when it is dry.
But these attributes of clay can also be good. When balanced appropriately in healthy soil, clay can hold to the roots of your grass water and nutrients that your lawn needs, causing it to grow strong and healthy.
In order to reduce your lawn the right way, you have to “amend” your soil with healthy additives that will balance the clay out so it can do its job instead of compacting it into thick unbreakable planes.
This process has two basic parts: aeration and top dressing.
Know What You Have
The first thing you should do is to make sure that clay is really your problem. You can either get a lawn testing kit from your local lawn and garden store or take a soil sample to your county’s extension office and have them test it.
Generally speaking, soil that globs up into giant sticky clods has too much clay in it. So, if after you’ve been walking in wet dirt in your backyard you feel like you’ve added a second sole to your boots, there’s probably too much clay in your soil.
Here’s a cool trick that can give you an idea of whether or not you have clay-heavy soil.
Take a small amount of wet dirt and ball it up in your hand. Then squeeze it flat to make a “ribbon” out of the soil. Extend the ribbon from your fingers until it breaks off. The length of your ribbon can give you an idea of the content of your soil. Fine Gardening breaks it down like this:
- 1 inch: your soil is probably made up of loam
- 1-2 inches: your soil is probably a mixture of clay and loam
- 2 inches: your soil is probably mostly clay
Source: Fine Gardening
Aerate Your Lawn
When you know for sure that you have unhelpful proportions of clay in your soil, you need to aerate your lawn.
Aeration is a process by which you begin to break up the clay soil by creating access points for water, oxygen, and nutrients, as well as for organic matter. This is a very important part of restoring your lawn and it’s a good idea to do it first.
Remember, your lawn’s big problem is that the clay soil is difficult to penetrate. There’s no point in top dressing your lawn if there’s no way for the organic material to get into the clay.
Check out our article, Starting A Garden In Clay Soil for more info.
When Should You Aerate?
Before you run out and rent your gear, take a few moments to think about when you’re going to aerate.
Generally speaking, if you’re in a hotter climate growing warm-season grasses, you want to aerate your lawn in the spring or early summer, right when things start growing again and lawn mowing season starts getting into gear.
- But there’s a hitch. If you’re going to aerate in the spring, you need to begin preparing the prior fall.
- Remember that the problem with clay is that it doesn’t allow water and nutrients to escape.
You don’t want to make your lawn’s problem worse, so in the fall, you need to rake deeply removing the layer of partially decomposed leaves and grass, called “thatch,” so that when you aerate, your soil is as accessible as possible.
You should also consider your general location, regionally speaking. If you’re in a northern climate growing cool-season grasses, you’ll want to consider aerating in the early spring or fall, as one help guide advises, when aeration is most effective for that part of the country.
How Should You Aerate?
There are three basic approaches to aeration that you can take:
- Spike aeration – this is a form of aeration that pokes holes in the ground. You can use a pitchfork, a spike aerator, or boots with spikes on them.
- Core aeration – this is done with a machine that removes plugs of grass and soil from the lawn.
- Liquid aeration – this involves getting a product to act as a wetting agent on your lawn that breaks down surface tension and can allow water to penetrate deeply.
Source: Thriving Yard
Spike aeration usually only works for small areas, and liquid aeration is still kind of new to the market, so the traditional and reliable method is core aeration. This is the easiest way to create access points for organic matter and get it as deeply as possible into as wide an area of lawn as possible.
You can rent an aerator at a lawn and garden store or a general equipment rental store, and you can set the depth of the aerator from ¾ inch to 3 inches deep. When you aerate go over your lawn several times, aerating in different directions.
Other Ways to Get Organic Matter into Your Lawn
There are a couple of other methods you can take to creating access points for organic matter to get into your lawn.
- One way is to drill out plugs from your lawn.
- This method is more unsightly than traditional aeration, since the holes are larger, and it represents a kind of heavy-handed approach.
- However, these holes have the advantage of creating large pockets of organic material in your lawn.
Once you have drilled plugs, you can fill them with organic waste such as coffee grounds and vegetable peels, and then allow them to penetrate the rest of the lawn.
Another, much slower way to create access points for organic matter is to make use of mother nature’s happy little aerators: earthworms. Earthworms burrow through your lawn consuming and creating organic material and dragging it along with them.
Earthworms are actually worth considering along with core aeration. Their natural up and down movement is a way of tilling the soil and allowing for better infiltration of water and nutrients to grass roots. For your established lawn, getting earthworm eggs is better than getting adult earthworms.
You can buy earthworms at a garden store or any bait store. Or, if there is an earthworm farm near you, you can get worm castings to use as organic matter for your lawn once you’ve aerated.
Here’s a helpful video about core aeration:
Top Dressing Your Lawn
Now that you have aerated your lawn, you need to get organic matter into the clay soil through a method called top dressing.
When you top-dress your lawn, you spread out organic material to a depth that covers your lawn evenly but does not cover the grass completely.
So, if your grass is 3 inches long, you can cover it to the depth of an inch. Usually, ¼ or ½ inch works.
It’s important to not cover your grass completely because it needs to be able to continue the photosynthesis process while the organic material is working its way into the clay soil, which will take some time.
It’s also important to allow the organic material to fill up those holes that you just made in your lawn. Remember, the whole point was to give an access point for the material that you’re spreading. Take full advantage of those holes!
Also, there’s no machine for this. The only way to spread this material effectively on your lawn is to do it manually.
Sometimes there are areas of the lawn that are particularly neglected, or sometimes the whole lawn is in pretty bad shape. In that case, you want to take this same idea but apply it more aggressively, rototilling the lawn to break up the clay before you add your organic material.
If there are small areas of your lawn that are particularly bad, you can break up the clay soil with a shovel and work your organic material into the soil with a rake, reseeding after you’re done.
What Type of Organic Material Should You Use?
Now the question is, what kind of organic matter should you use for top dressing your lawn. You may need to do this once or twice a year.
First, what is organic matter? Generally speaking, it’s the stuff we think is dead but is actually very active with microbial life. Dried up leaves, grass clippings, banana peels, all these things have a lot going on that we can’t see.
Clay needs more organic matter, primarily for texture reasons, not nutrients. Clay already has a lot of nutrients. The problem is that it won’t release them. When organic matter gets into clay, it loosens up those small tight particles, allowing water, oxygen, and nutrients to pass through.
This is where having a specific analysis of your soil is going to be very important. It’s not enough to know that you have clay. How much clay do you have? What kind of amendment is going to help?
Some amendments work only for specific soil treatments and applying them in the wrong conditions can cause more harm than good. There are also some differing opinions out there with regards to certain methods.
With that in mind, here’s a look at some soil amendments that you can use when top dressing your lawn.
Humic Acid
At the end of the line of organic matter decomposition, you find humus. In the natural sense, that includes plants and animals. Humus makes soil dark and crumbly which allows water and air to pass through it easily. It is also loaded with nutrients.
One key component of humus is humic acid. The word acid here refers to the structure of the molecule, not the function. Humic acid is not like sulfuric acid for example.
Nevertheless, applying humic acid as a top dressing can help break down clay and allow for better water and nutrient penetration to roots.
Manure
There’s a surprising amount that can be said about manure. In brief, don’t try to use fresh manure because it has too much nitrogen. Manure needs to sit for at least a year before you try to use it on your lawn.
Furthermore, be aware that different animal manure has different nutrients. Some of that may have to do with what the animal eats, so know your animal poop before you spread it around.
For example, horses and cows may pass a lot of weed seeds into their manure, which could create a growth explosion of the kind of plants you do not want in your lawn.
If you want to use manure for top dressing your lawn, buy composted manure at your local lawn and garden store. Manufacturers make different compost for different amendment needs, and your store professional can help you choose which one is right for you.
Gypsum
One of those amendments that are heavily debated, gypsum is made up of about 23% calcium and 18% sulfur and it does not affect the pH level of soil. A lot of claims seem to be made about gypsum, but we’ll only discuss its uses as relevant to clay.
Gypsum can positively affect clay-heavy soils by improving the texture of the soil and reducing compaction. This is an instance where the analysis of your soil will be very useful.
After Top Dressing
Once you have completed aeration and have done the top dressing of your lawn, now you need to keep the process going.
More Organic Matter
Remember that the whole point of top dressing was to use organic matter to reduce the compaction of clay in your soil. You can keep providing your lawn organic matter even after top dressing using a simple technique: mulching.
Grass clippings in the summer and leaves in the fall are ready to order organic materials that don’t take a wheelbarrow, a shovel, and a strong back to spread. It only takes a lawnmower.
By removing the bag of your mower and leaving the grass clippings and mulched leaves on your lawn, you are using the natural process of decomposition to your advantage.
Water
As you nurture the soil of your lawn to a healthy balance, consider some of these tips about water and drainage.
Grass roots are often shallow in clay soils, and if you water frequently and lightly, that encourages a state that you don’t want your grass to be in. The whole point of reducing clay is to get better growth and a greener lawn.
Now that you’ve done the work to set up the reduction process, water your lawn less frequently, but more deeply. This will encourage the roots of your grass to go deep for water, especially as clay compaction lessens. Give your lawn 1 inch of water a week.
Something else to keep in mind with water is drainage. When the rainy season comes, you don’t want to take a step back by letting your lawn get waterlogged, thus leading back to compaction.
Installing a drainage system in your lawn that leads water away to a rock feature in your yard or simply to the storm drain, lessens clay’s chance to hoard water under your lawn.
Don’t Walk on the Lawn
The advice your elementary school teacher gave you on class walking trips is applicable here. Stay off your lawn. It will eventually be the lush field of sports and activity that you want it to be, but while your soil is in the process of reducing clay, stay off.
Remember, clay wants to compact, and the more you walk on your lawn the greater the chance of it happening again. Hunker suggests these methods of keeping people off the grass:
- Lay stones or install sidewalks to create paths to and from structures.
- Establish seating and playing areas by building a deck or laying mulch.
Remember, reducing clay in your soil the right way takes time and patience, but with a concerted effort on your part, it can happen.