Selecting a bag of soil at the landscaping center can be confusing because there seem to be so many different bags of soil available. Even though topsoil vs lawn soil sounds the same, they are actually pretty different. So, depending on what project you are doing, you might want to pick one over the other. Therefore, let’s take a closer look at what’s actually in these different bags and see whether lawn soil vs topsoil is best for your lawn project.
The Difference Between Topsoil and Lawn Soil (The Short Answer)
The different layers of soil in the ground are called horizons and make up the soil profile. Topsoil is classified as A-Horizon and generally consists of sand, loose dirt, and healthy microbes. Whereas lawn soil (subsoil) is B-Horizon and generally consists of rocks, clay, and dirt. Therefore, topsoil would sit on top of lawn soil in a natural environment.
Upper Soil Profile
- Layer 1 O-Horizon – Organic
- Layer 2 A-Horizon – Topsoil
- Layer 3 B-Horizon – Subsoil (Lawn Soil)
What is Topsoil?
Topsoil is the top layer of soil that sits beneath the layer of organic decomposing material, such as fallen leaves, dead plants, and grass clippings. Sand, loose dirt, and healthy microbes make up topsoil, which is a perfect living environment for plants.
Topsoil provides good drainage, is loose enough for natural soil aeration, and allows nutrients to pass through from the organic layer easily which is ideal for plant health. So, topsoil provides a great foundation for plant roots to feed and grow.
Are All Topsoils the Same?
Depending on the source of your topsoil, you’ll find a variation in the level of included organic matter. Now, this may not be a big variation, as topsoil is usually pretty standard. But there is definitely a difference, and mainly depends on where the topsoil comes from and at what point in the horizon it has been harvested. Will you and your lawn know the difference? Probably not.
What is Lawn Soil?
Lawn soil is much denser because the upper layer of topsoil naturally compresses lawn soil (subsoil). Therefore, even though lawn soil will still have nutritional benefits, it is less fertile than topsoil. Also, due to the compressed nature of lawn soil, water drains much slower through it, trapping nutrients and making it harder for roots to penetrate.
Are All Lawn Soils the Same?
Lawn soils are definitely not all the same, and this is where it gets confusing. A traditional or, should I say, real lawn soil is a subsoil and has specific properties. But this is a very loosely used term. Manufacturers such as Sta-Green and Scotts both produce large bags of soil labeled as lawn soil, but on closer inspection, these materials are actually blends of different soils.
For example, you’ll find a blend of horizons O, A, and B mixed with starter fertilizers. To make things even more confusing, you’ll find real lawn soil, like plain and simple Horizon B soil. Some people call this fill dirt. So, don’t be fooled by the name. Always check what’s in the bag by checking the label.
Top Soil vs Lawn Soil: Comparing the Two
When deciding between lawn soil vs topsoil, it’s important to work out what you are trying to achieve. This is because each of the soils will act very differently depending on what task you are trying to complete. So, let’s look at a few factors that will help you decide.
Cost of the Different Soils
One of the first things you’ll notice is the price difference between topsoil and lawn soil. This is because topsoil is in far greater demand. So, depending on your goal, don’t overpay for topsoil if it’s not what you need.
Filling Holes & Raising the Ground
One common job around the yard is to fill holes or level out the ground. You might do this when you’ve removed a plant or where you have a dip in your lawn. Depending on how deep the hole or depression is will determine what type of dirt you use. For example, if you only want to raise an area a few inches, then topsoil is the best option, as areas like lawns really only need a 4-inch topsoil layer, and you want the benefits of topsoil.
But if you have removed a tree and you have a big hole, then you’ll want to fill the hole with lawn soil and then top it off with 4 inches of topsoil. You want to do this for two reasons. First, you’ll recreate the soil profile. Second, it makes sense cost-wise. The subsoil will slow drainage and help to keep the topsoil hydrated. The area will dry out quicker than the rest of your yard if you fill a big hole with just topsoil.
Improving Drainage
You should consider drainage in two ways: too high and too low. Depending on what you are trying to achieve, you’ll need to pick the right soil. For example, if your soil is always wet, you probably already have a thick layer of subsoil and a thin layer of topsoil.
So, adding extra topsoil will help the water drain. For areas that are always dry, then you probably have a thick layer of topsoil or some other type of upper layer, such as sand in coastal areas. Therefore adding lawn soil will help. But in that case, you need to be careful because subsoil is not good for growing plants, and you’ll want to use a blend.
Soil Amending
What is soil amending? Well, this is where you are fixing the soil to help plants and lawns grow. If you have ever wondered how lawns grow out in the Arizona desert, it’s because the arid landscaping has been replaced with soil layers and has been amended.
Now, this is an extreme case, but you might have something similar on a smaller scale that needs addressing. For example, topsoil will help to improve the quality of your soil and meet the requirements of your lawn and plants, as topsoil will hold nutrients, provide drainage, and give the roots a good source of air.
On the other hand, lawn soil will help slow nutrients and water from disappearing too quickly.
Should You Use Lawn Soil, Top Soil or Both on Your Lawn?
Personally, I would topdress my lawn with topsoil and only use real soil as fill material. But I would mix both soils and use them as a top dressing. This is a homemade blend of soil mix and basically the same product that Sta-Green and Soctts produce.
The benefit of blended soil or blended lawn soil is that you get the benefits of both Horizon A and B at the same time, and you don’t need to rip your yard apart. Of course, in an ideal world, your lawn would sit on top of perfectly measured soil layers. But unless you want to tear out your lawn and start again, this isn’t possible.
The one big thing you should avoid when using real lawn soil (Horizon B subsoil) is using it alone as a topdressing layer. This is because the high percentage of clay and dense dirt will slow/stop water filtration and turn your lawn into a pond.
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