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Clay soil can be a real pain and I have been struggling with it for years. When you are preparing soil for grass, you have a lot of options. But when you need to amend clay soil without digging, for example with an established lawn that you don’t want to mess up, you have to be more particular. I’ve worked out a five-step process over the years for improving clay soil under an existing lawn or just improving drainage and texture.
Five steps to amend clay soil without digging:
- Soil Conditioning
- Core aeration
- Deep Soil Integration
- Mulching (for existing lawns)
- Topdressing with nutrient-rich organic matter
Let’s break down each of these steps and look at what they do, why they matter, and how they can help you to improve your soil.
But first, let’s settle one longstanding debate.
Topdressing Alone Is Not Enough
One of the most commonly promoted methods for improving clay soil is topdressing. I hear it all the time and it’s probably the first suggestion that you’ll be offered if you ask someone about improving your clay soil lawn without tearing up your grass.
I get it.
Incorporating a nutrient-rich organic matter remains the most important aspect of improving the texture and quality of clay. But the idea of simply spreading a layer of good soil over an existing layer of compacted clay has one fatal flaw and it’s best demonstrated with a picture.
My wife is a fan of these layered deserts. They remain in distinct layers until the substances are mixed. Then, they become something new, something integrated and different.
That’s what is missing from the topdressing alone approach. You are simply putting a layer of good soil over a layer of clay. Since clay compacts tightly, it does not aggressively leach in the nutrients and added benefit of soil texture from the top layer.
The top layer just sits there, until it washes away. Yes, it will help your grass and there will certainly be some soil that will sink down into the grass and stay. But it’s not addressing the underlying issue. It’s not actually improving or amending the clay soil underneath. It is simply hiding the problem.
The solution is to not just drop the organic matter on top but to literally infuse it into the clay.
Don’t misunderstand. Topdressing is important and we will definitely be incorporating it into our soil improvement strategy. But it is actually the last step of the process. We need to do a few things first before applying topdressing so that we get the maximum benefit.
So here is the five-step approach to amending clay soil. It’s the same approach I use in my yard.
I’ve seen plenty of controversy over whether or not liquid soil conditioners help to improve clay soil. The active ingredient in most of them is the same ingredient that you find in shampoos. What the conditioners do is to soften the surface of the soil, allowing for nutrients to leech in and promote a texture that allows for natural biological activity to take place, something that hard clay prevents.
Another benefit in our scenario is that it softens the soil so that we can aerate and perform deep soil integration more effectively (more on this below). For this reason, I find it best to do this step first.
To better understand the effectiveness of liquid aeration and what it does (and doesn’t) do read our article Does Liquid Soil Conditioner Work? The Easy Aeration Promise
In the past, I’ve mainly used a product from Simple Lawn Solutions. Amazon carries this product and you can check the latest pricing by clicking here. You spray it liberally onto your yard using a garden hose automatic mixer. It only takes a few minutes but is an essential part of the 5 step clay soil improvement strategy.
Core aeration literally results in plugs of soil being removed. This is not the same as sticking spikes into the ground or those goofy spike shoes. That will only result in compressing the soil around the holes even more.
Renting a core aerator is one option but those rental fees can really add up. If you have a riding mower this pull-behind core aerator is an excellent option (link to Amazon). It has 24 plugging spoons made from 16 gauge steel. You add weight by filling the bin on top with cinder blocks, bricks, large rocks, or anything else that is heavy. This compresses the spoons into the ground as you pull it and the spoons rotate, pulling plugs of soil as it goes.
Most lawns can get by with aerating once annually or even every two to three years but with a heavy clay lawn, I find it beneficial to do this twice a year right as the season warms and as it begins to cool.
But core aeration is only part of the solution. We can’t just pull plugs of clay out and call it good. Remember, our goal is to truly infuse nutrient-rich matter into the clay.
Deep Soil Integration
I promised no digging. I will keep to that. But it’s important to understand why digging and tilling are such mainstays in clay soil amendment.
They allow better soil or compost to be mixed and integrated with the clay. And the deeper that mixture can go, the better the longterm results.
That being said, I realize may not be crazy about digging holes in your yard, especially if you have an established lawn. The core aeration is going to help us get that organic matter down a few inches. But we really need to go deeper if we want to truly transform the composition of our soil.
This is a method that I call Deep Soil Integration. I’ve been doing this in my yard since 2016 and it has made a remarkable and undeniable difference. And it’s a technique backed by science. Studies have confirmed that burying organic material improves the conditions of soil (source).
The process involves using a large drill auger bit similar to this one (link to Amazon) that is designed to speed up the process of planting bulbs. The way I use it, however, is to drill down deep and fill those holes with organic matter like compost or just fill them with organic material such as kitchen scraps and use them as cold compost holes.
Yes, it does leave holes in your yard but we are doing to address that below. And your grass will grow back over the holes quickly anyway.
This is a critical step. It takes the care of your clay soil yard to an entirely new level. When doing this, you are removing clay soil deep into the ground and replacing it with organic materials that will promote worm populations, improve drainage, and allow for deep root growth.
If you would like to learn more about how I use this technique to improve my clay soil lawn, read my full article, The One Trick To REALLY Improve Clay Soil – Deep Integration.
If you have a healthy, thriving lawn, there is a benefit to bagging your grass clippings and using them to make compost. But if you are struggling with growing a lawn in clay soil, mulching is an excellent way to provide essential nutrients like nitrogen and improve the clay soil (source).
Best of all, it’s essentially a passive effort. You are going to be mowing anyway. Instead of bagging your grass clippings you use a mulching blade and let it tear up those clippings and push them back into the grass surface.
I’ve known this was an important step for some time but wasn’t using it due to not having a mulching blade. I invested some time one Saturday morning and installed these blades on my John Deer riding mower. I have zero regrets. It just makes good sense when dealing with a clay soil lawn, especially as part of the comprehensive soil improvement strategy that we are using.
Topdressing: The Final Ingredient
Remember that we started with the premise that topdressing alone is not enough. But it is an important final ingredient to our 5 step process. Here’s a breakdown of how these steps work together and how the topdressing finishes off the process.
We began by applying a liquid soil conditioner to soften the surface area of the clay soil. This allowed for us to more effectively use our core aerator and drill for deep soil integration. We may have dropped some leftover kitchen scraps or compost into those holes but if not, it’s no issue because we’re doing to address it.
We then mowed our yard using a mulching blade. Some of those nitrogen-rich grass clippings were blown into the core aeration and drilled holes in our yard. And now, we top off the area with a nutrient-rich topdressing.
The topdressing is spread over the lawn and is allowed to fill the holes caused by the aerator and drill. It’s important to spread the remainder of the topdressing evenly over the yard so that your grass blades are not covered. Now, let’s take a close look at what we’ve really done.
Instead of just spreading a topdressing over the surface, we have created a mixture of shallow (core aeration) and deep (drilling) pockets in the clay soil throughout our yard. We’ve then let our mulching blade throw in some grass clippings and filled the holes with topdressing. This will significantly change the overall texture and composition of our clay soil with time as worms find it easier to burrow through the soil.
Can you see the benefit of this approach? Like the layered desert, we are doing more than just putting a layer of topdressing on the surface, we are literally infusing nutrient-rich topdressing deep into the clay soil itself, changing the composition of the soil until, over time, it becomes something else entirely.
Growing a healthy, thriving lawn in clay soil has it’s challenges but with a comprehensive soil improvement strategy and a little time, you can make significant improvements. These are real strategies that I use on my two-acre yard and I have seen remarkable results from my efforts. I didn’t drill the entire yard in a day. I focus on an area at a time and work that area.
I’ve found that it’s best to aerate twice a year: in very early spring and late fall. I always prep the ground first with a soil conditioner so that the core aeration spoons can dig in and really pull out that nasty clay.
If you are really frustrated with the clay soil in your yard like I was, I would encourage you to try out this 5 step approach. My yard is a testament to its effectiveness and every year I see a little more improvement. Now that I’ve added mulching to the recipe, I’m confident that I’ll reap even great rewards each season.
See The Results From A Reader Who Used Deep Core Integration To Improve Her Yard
Dig into the details of improving clay soil with our complete guide: Improve Clay Soil for New Or Existing Lawns.