If you’re going to the trouble of having a lawn, you might as well make it as lovely as possible. If you’ve got great soil, much of the work is already done for you. If your soil is harder, denser, and compacted, you’ve got problems. So how do you grow grass on hard-packed dirt?
We’ll take a look at why compacted soil is hard to grow things in, including grass, and we’ll take a look at a few ways to remedy the problem. We’ll also take a look at some different grasses to give you an idea which ones would be most successful.
Compacted soil is one of the most difficult growing mediums there is. Plants have to spend a lot of energy pushing roots into hard soil and less for actual growth above the ground. It makes for difficult going if you’re growing garden vegetables, and it also makes for poor lawns.
There are solutions to this, some requiring hard physical labor. But the first step is knowing how to address compacted soil.
We’ll set out to tell you how to do it, focusing on working smarter and not harder. You should also consider it an investment of your time. Soil gets compacted because it’s been neglected, and it’ll take some time to set it right.
Grass also tends to grow best in soil that shades a bit to the sandy side, because the large granules are easier for grass roots to push through than tightly packed small granules. So, we’ll also take a look at a few different kinds of grass that you can try that work well in harder soils.
Finally, we’ll take a look at how to manage your soil long-term. Your lawn is an important part of your property. A lush lawn will make it more valuable. One that is difficult to grow, a good deal less so. You’ll want some tips on how to keep your soil nice and loose, and we’ll provide them.
Hopefully, by the end, you’ll have some solid ideas on how to grow grass in soil that is compacted.
Compaction and why it happens
Any kind of soil can get compacted, but it is most likely to happen in soils that have a high clay content. There are three basic types of soil: Clay, silt, and sand. Clay is comprised of the smallest granules, and if you grab a handful of it and squeeze it, it will form a tight ball. If you poke that ball with something, say a finger or a stick, it will retain its shape. Clay also doesn’t drain very easily. It holds on to water.
On the other hand, if you squeezed a handful of silt into a ball, it would retain its shape but fall right apart if you poke it with something. Sand falls apart immediately after you release it.
Most soil is some kind of combination of at least two of the three, but soils with the highest clay content tend to be the densest, making them most likely to become hard and compacted. Just remember that aside from soils of pure sand that any soil can become hardened.
Soils can get compacted in a lot of ways. The first, and most common, is that it gets a lot of traffic. If you’ve ever wondered how a path through the forest can remain clear of vegetation, it’s because that path gets used enough that its soil has gotten pushed down and compacted. Nothing is growing on it because it keeps getting used. The same can happen to a lawn, especially where there are children who run around on it.
Another way is that the soil gets neglected. If you leave soil alone and don’t take steps to loosen it up, over time gravity will compact it naturally. This is most common with soils with very high concentrations of clay because in better-balanced soils plants tend to take root and break up the soil naturally. When dead plants decompose, they also tend to loosen up the soil as a natural amendment.
Why compacted soil matters
Imagine trying to push your finger through aquarium stone and then trying to push it through nearly dry cement. The aquarium stone offers less resistance. It just gets pushed to the side as your finger slides in.
The cement is the equivalent of compacted soil and your finger is the equivalent of a plant root. While your finger can penetrate the cement, it is more difficult and requires just a little more energy.
While it might require a little more exertion for you to push your finger in, for a plant it requires a good deal of its energy. Where plants have to expend a good deal of energy spreading roots, they have less of it to put into the foliage and fruit of what happens above the soil’s surface.
Compacted soil makes it more difficult for plants to grow and thus they tend to be smaller and put on less fruit. When it comes to grass, that means it’s shorter and doesn’t fill the area in as well. It might not be totally bare, but it might look thin and weak. Who wants that from a lawn?
As a side note, if you are looking for a great article on the best soil type to grow vegetables, you should take a peek at our guide right here.
When to get your soil tested
Your state’s Extension service probably has a program to test soil and provide you what its characteristics are. It’ll go through the basics, like the soil’s ph-level and its nutrients loads. They might also be able to tell you its content of clay, silt, and sand. If it has a high content of clay, when you loosen it, you can add some sand to help keep the soil broken up.
If you do this, make sure it’s a project you’re willing to invest in. If you need to amend your entire lawn, because it has a high concentration of clay, it might take several growing seasons to do all the work. If you are keen on having a lush-looking lawn, it is probably more worthwhile than if you are not so concerned.
Loosening your soil
If you want to grow anything in compacted soil, the first step is to physically loosen it up. If it’s a small patch, a shovel is probably your best bet. You won’t save a lot of time using a rototiller and it might be a pain in the neck hauling one out if there isn’t much work to do.
For large patches, you’ll want to use a rototiller. Set the depth gauge to six inches, which is where most grass roots grow. If you got your soil tested and it came back with a substantial portion as clay, sprinkle sand and/or silt over the top of it as well as any fertilizers and compost.
The compost will help loosen the soil and add some nutrients, but it will also break down as it decomposes. One cubic yard per 1,000 square feet of lawn will work.
Till the soil, working backward to avoid stepping in newly tilled soil. Stepping on it will just compact it all over again. Probably not to the degree that it was before you tilled, but it’s best to just avoid it. Make sure you do this when the soil is dry. Tilling wet soil can cause it to compact.
Once the area is tilled up, rake it to even it out.
Which grass seed to use
You don’t just want to toss grass seed on the tilled earth, you want to choose a grass that will thrive in your soil.
Cool-weather grasses tend to be more suitable for harder soils. They tend to grow in clumps and have roots that drill down deeper into the soil. So, they have a better chance for success than a warm-weather grass, which is better suited for sandier soil.
Your first criteria should be what kind of grass is growing around the bald or thin patch. If you don’t what kind of grass it is, contact your local Extension office for help identifying it.
Remember the aphorism “The grass is always greener on the other side?” You don’t want to modernize that as “The grass is always greener where the kids played kickball.” Make sure what you’re planting at least very closely resembles the rest of the yard.
If you’re free to pick a new kind of grass, we’ve got you covered for that, too.
Annual ryegrass is one choice. One advantage to ryegrass is that you can plant it without tilling the soil, which can damage it. Farmers use it where they practice no-till farming because it can break up the soil without willing. It also adds nitrogen to the soil naturally. If you don’t want to manually loosen the soil, it’s a good choice. You’ll need five-to-six pounds per 1,000 square feet.
Tall fescue is another choice, especially if you have clay-heavy soil. Its deep roots not only compensate for the clay, but they will also help it withstand droughts better. It’s a cool-weather grass, which means it grows best in fall and spring and goes dormant through the hottest part of the year. The best time of year to plant it is in the fall, as its most active growing season starts. Plan to use four-to-five pounds per 1,000 square feet of lawn.
If you live in the southern states, zoysia is a good choice. Like tall fescue, it has a dense root structure. It’s also a warm-weather grass, so it is most active during the warmest times of the year, going dormant in winter. Plant it in late spring, right before its most active period of growth, and you’ll need one pound per 1,000 square feet.
From germination to establishment
Use a seed spreader to lay the seeds down, and make sure you have it set properly. You don’t want to overseed.
Once it’s down, lay a thin layer of straw or hay mulch over the top and thoroughly water the entire thing. A good guide is enough water to soak the soil to a couple of inches’ depth. Remember that if your soil has a lot of clay that it won’t drain as well. So, be sure to avoid overwatering the grass seed.
Keep this up until the seeds have germinated and are well on their way to being established. Young plants are more vulnerable to drought than older plants because they lack the root systems to tap into water below anything but the surface. You’ll want to keep at it on a regular schedule until the grass has established itself.
Your work isn’t finished when the grass has established itself. You’ll need to do additional work to maintain the grass, especially if it gets a lot of traffic from kids and pets.
Four times a year, fertilize with a slow-release nitrogen fertilizer. You don’t want it releasing too quickly because too-much nitrogen in a short time can scald plant tissue. Use from half a pound to one pound per 1,000 square feet.
Once or twice a year, when the soil is dry but rapid growth is taking place, aerate the soil with a soil aerator. Try to remove cores down to three inches.
And, always remember, mow with a sharp blade.
Grass isn’t the hardest plant to grow, but it can frustrate you if your soil is compacted. Roots will have a harder time spreading, which means they’ll have a harder time getting water and nutrients for the blades.
Soils high in clay content are the most likely to become compacted, especially if they are in a high-use area. Over time, however, gravity will compact soil unless it is kept loose either by plant and animal activity.
There are two primary ways you can grow grass on hard-packed soil. The first is that you manually loosen it. If you go this route, you’ll want to get the affected soil tested for nutrient load and how much of the three basic soils it’s comprised of.
The results of this test will tell you what you should add to your soil to keep it loose. You’ll add some kind of compost, but you might also want to add some soil. You’ll also get an idea of what kind of fertilizers might be helpful. Because grass is just a blade and a root structure, assume it’ll be some kind of nitrogen.
Sprinkle what you’re blending in on the soil before you turn it.
If you need to loosen a small patch created by active kids, you can do that with a shovel. Otherwise, use a rototiller set to a depth of six inches. Make sure you pull the tiller behind you so you don’t step on previously tilled soil.
Once you’ve tilled the soil, sprinkle your seeds on it. Make sure you’re using the correct amount for the grass you’re planting. You want what you’re sewing to blend in with the rest of the grass, not stand out.
An alternative if you prefer to avoid tilling is to pick a grass seed with a proven track record of breaking up hard soil. In the north, ryegrass is a good choice. So is tall fescue. In the South, zoysia grass is a smart option. All of them put down deep-reaching root systems that will slowly break up compacted soil.
Water it so that the ground is good and wet and cover with a light layer of hay or dried straw. Until your grass establishes its roots, the individual plants are especially vulnerable to drought.
Just because your grass is established doesn’t mean that your work is done. In addition to mowing with a sharp blade every single time, you’ll want to fertilize a couple of times a year with slow-release nitrogen pellets. At the start of every growing season, aerate the soil with a soil aerator.
We hope you found value in our guide. Lawns are important investments and can have a significant impact on your property’s value if you try to sell it. We wish you good luck in repairing your lawn so you can have one that is the envy of the neighborhood.