Topsoil vs. Garden Soil: Differences, Uses, Amendments

Topsoil and Garden might look the same, but there are some substantial differences beneath the surface.

When soil scientists are talking about topsoil, we are typically referring to the top 12 to 25cm of the earth. But landscapers are talking about ‘fill dirt,’ which is designed to fill in holes, cover large areas, or help with contouring. Garden soil is of higher quality and more expensive, so it is used more sparingly. It has been amended (improved) with compost, manure, or fertilizers.

The following table will help you to understand the difference between the two soil types:

Generally speaking, plants are going to do better in Garden Soil than Topsoil. But the very best Topsoil can be more successful than the worst Garden soil.

Unfortunately, if you (or your soil provider) don’t know what you’re doing, your Garden Soil might be teeming with pests and pathogens.

This article will give you a well-researched and up-to-date comparison of Topsoil and Garden Soil.

It will help bust some of the myths around soil, so you can take better care of your plants while protecting wildlife and saving a bunch of money.

I hope you find it helpful!

Topsoil, Definition, Uses, Types & Textures

What Is Topsoil?

In landscaping or gardening terms, Topsoil is lower quality soil that can cover a large area.

For example, someone might import a truckload to fill in an unsightly ditch.

It might also be helpful in a situation where the natural topsoil was washed away by erosion.

It would be far cheaper to replace missing soil with Topsoil than Garden Soil.

What Is Topsoil Used For?

You would need Topsoil after a constructive project has finished when the garden space has been compacted or eroded by heavy machinery.

You might want to spread a thick layer all over the degraded land to help it recover more quickly. (And so you’ve got something to plant in).

(If you want to check the compaction level in your yard, it’s straightforward to do using a penetrometer.)

Topsoil could also fill in a drained pond or level out steep contours. (Who wants to dig potatoes on a treacherous slope?)

I also know someone that used Topsoil after a landscaping project ended in disaster.

A well-intentioned (but beginner) gardener had sprayed their entire lawn with an aggressive pesticide that has killed off all the plants, worms, and microorganisms.

They had to import several truckloads of top-dollar topsoil to put it right.

New soil should be as local as possible, though. Native microorganisms will be adapted to survive in your climate.

Different Topsoil Types and Textures

Soil texture depends on the balance of three particles: sand, silt, and clay.

All three types started as mountains and huge rocks, but they’ve broken down due to the weather, chemical reactions, and the hard work of microorganisms.

Sand is the biggest particle, but clay particles are so small that you’d have to put them under an electron microscope to get a glimpse of them.

Growing can be challenging (but not impossible) if your topsoil has too much of any one of these soil types.

Ideally, you want a balance of all three, which would give you the highly desired loam texture.

Having said that, you can get the particles to act differently if your soil is thriving with beneficial bacteria, fungi, and predators.

Even an expert might look at your clay Topsoil and think it is a perfect loam.

This is because all the critters living in the soil stick the tiny particles together with their natural slimes and glues. (Lovely, I know!)

What does this imply for you? Well, it means that a healthy community of bacteria and fungi is more important than your initial Topsoil texture. (Sorry old-school gardeners, the science has spoken!)

Best Way To Improve Topsoil

The best way to improve topsoil is to understand the problems you’re facing and address them at the root.

The two main problems with topsoil are compaction and not enough beneficial microorganisms.

I will address how to solve these problems below.

Soil Compaction

If you’re experiencing compaction, water is not going to able to infiltrate into your soil correctly.

As a result, you may have problems with topsoil being washed away by the excess rainwater.

This means frequent, expensive replacements of soil and plants.

You will also be wasting money on frequent watering because rainwater will be pouring off the surface instead of penetrating deep into your soil.

Solutions to compaction:

Stop using heavy machinery.
Stop or drastically reduce tilling (including rotavators that fluff the top layer while making compaction below the surface even worse).
Plant cover crops like these, so the rainwater is never hitting the bare earth and making the problem worse.

Once you’ve dealt with compaction, your plant roots will be able to reach much deeper into the soil.

As a result, they will become healthier and more resilient for years to come.

Not Enough Beneficial Microorganisms

Plants have a reciprocal relationship with beneficial bacteria and fungi in the soil.

For example, some bacteria fix nitrogen in the roots of plants, and some fungi will collect water for the plant in return for sugars from photosynthesis.

Beneficial bacteria and fungi also cover all surfaces of plants, creating an armor against pests and diseases.

In addition, predators that eat bacteria and fungi (protozoa/nematodes) excrete excess nutrients in plant-available form.

The more organisms in your soil, the better the environment for your plants!

How to encourage beneficial microorganisms:

Introduce beneficial organisms through good compost, worm castings, and compost teas
If possible, stop using pesticides and fungicides (they kill just as many ‘goodies’ as ‘baddies’).
Replace tilling or rototilling with no-dig practices. (Disturbing the soil will kill your microorganisms).

Once you’ve got a good community of bacteria and fungi, you won’t need to use chemical pesticides or fertilizers.

As a result, you’ll save lots of money, and you will reduce toxic inputs that can harm your family and wildlife.

Your plants will be more resilient to diseases and pests, and your yields should increase.

You will also notice a reduction in weeds over time.

Garden Soil Definition, Uses, Types & Textures

What Is Garden Soil?

Garden Soil is more expensive than Topsoil, so you’ll probably be buying or making it in smaller amounts.

You would use Garden Soil in raised garden beds and pots rather than spreading it over huge areas.

It has a base of Topsoil, but it’s been mixed with manure, fertilizers, or compost to make it more punchy.

What Is Garden Soil Used For?

I would use garden soil in pots, where my plants will need to find their food and water in a smaller area.

I would also use it in raised beds, but I might further dilute with topsoil if my beds were large.

If you’ve just covered a large area with topsoil, you might be planting seedlings or saplings at regular intervals.

You could dig a hole for your young plant and mix in a healthy dose of garden soil around the roots to help give it the best start in life.

Different Garden Soil Types and Textures

Your garden soil will probably be sieved, so it doesn’t contain rocks or lumps.

However, depending on where you got your garden soil from, you might find it has clumps of manure.

This comes from the misguided idea that “manure is great for plants.”

We need to replace that idea with: “well-rotted, aged manure can be great for plants.”

If you are looking in your garden soil or compost and still see manure in it, it isn’t ready to be used on plants.

You can safely assume that it’s got human and plant pests and pathogens in it, and it shouldn’t be applied to your garden, especially if you’re producing food in it.

Don’t get me wrong, I love using manure in my garden. I make my compost with around 10% manure, which helps get it up to temperature.

A good garden soil that is ready for use shouldn’t have big clumps of anything in it.

But it’s ok for it to have some texture. Some texture means that the soil is going to hold water much better.

But you want a grainy texture rather than big lumps of manure or uncomposted organic matter.

Best Way To Improve Garden Soil

Just like Topsoil, the best Garden Soil will be thriving with microorganisms. So if you’re doing it right, Topsoil and Garden soil can be quite similar.

Some people choose to improve their garden soil with chemical or organic fertilizers, such as calcium or gypsum.

However, this would be a short-term and expensive solution.

If you don’t have microorganisms in your soil, the rain will wash away most of the minerals and nutrients.

This is a waste of your time and money, but it can also call algae blooming in local rivers and streams, which in turn depletes the oxygen in the water and can wipe out the native plants, fish, amphibians, birds, and insects living in that community.

But plenty of fungi and bacteria will stop this from happening.

They create natural glues to stick to each other and soil particles, which bind soil into aggregates.

They also hold nutrients in their bodies, which are released when predators like nematodes or protozoa (more microscopic organisms) eat and then excrete them.

But if you have the right balance of microorganisms, you don’t need any additional fertilizers.

Instead, your bacteria and fungi will be busy breaking down the tiny soil particles and releasing the nutrients stored in the rock material.

If you want to improve your garden soil with microorganisms, you can spray it with compost tea or inoculate it with fungi and other microscopic predators.

Worm castings are also a brilliant way to improve your Garden Soil.

You can even produce your own by using a vermicomposter.

Just bear in mind that vermicompost (from worm bins) doesn’t heat up, so seeds can still be present.

So if you buy worm castings, they should have been heat-treated, so you don’t get random plants you didn’t bargain for popping up in your garden.

Can You Mix Topsoil With Garden Soil?

If you’ve got fantastic Garden Soil, you can dilute it with Topsoil.

I wouldn’t recommend tilling the Garden Soil into the Topsoil because this can kill the microorganisms and break up the beneficial fungi.

I know I keep going on about those tiny critters. But they are the key to thriving gardens, farms, and ecosystems.

You would be better off mixing the soils in a bucket with a small spade.

The concentration of each will depend on what you’re growing and the quality of your soils.

It might take some experimenting, but that’s the joy of gardening!

Each coming year, you’ll need to add fewer amendments to your topsoil because you’ll have established such a healthy web of microorganisms in your soil.

For more on the Soil Food Web, you’ll want to check out the work of Dr. Elaine Ingham.

Best Soil Mix for Vegetable Garden

There is no one perfect recipe for Garden Soil.

But generally speaking, you’d want around 60% Topsoil, 30% compost, and 10% potting soil.

Then again, no two composts are the same.

If your compost provider follows legal guidelines, you shouldn’t have a problem with pests and pathogens.

But the regulations don’t state how much bacteria and fungi you have to have in your compost.

That means you could be buying dead, rotted waste material rather than living, thriving soil.

If you’ve got fantastic compost that is full of beneficial organisms, you might be able to use much less than 30%.

You don’t have to use potting soil, but it helps with drainage.

This means that the rainwater can move through the soil more efficiently, and you aren’t going to have so many problems with waterlogging.

Having said that, a good balance of microorganisms will create aggregates with their natural glues, and drainage won’t be a problem.

Recommended Topsoil

Lots of articles online will link you to some recommended topsoils to make an affiliate sale, but I want to be completely honest with you.

When it comes to topsoil, the more local, the better.

If you get your soil flown in from another climate, it’s unlikely to be suitable for your conditions.

This is because the microorganisms will be adapted to different conditions and may not survive in your yard.

Otherwise, the long-distance transport could have wiped out all the life in your soil, which would be equally bad.

You should find a topsoil provider as locally as possible, which you can do by searching something like ‘Topsoil in Wyoming’ in Google.

Ideally, you want organic topsoil, so you aren’t killing your existing microorganisms with pesticides.

Peat-free soil is always best because peat is a vital carbon sink and delicate habitat which the landscaping industry has overexploited.

The industry is catching up now, and peat-free soils are increasingly available!

Recommended Garden Soil

If you cannot make your garden soil, you might like to try some Miracle-Gro All Purpose Garden Soil.

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It contains plant food, which isn’t going to be necessary once you’ve restored your soil. (The plant food will be extracted from the soil particles by your biology).

But it’s a good idea to use some plant food at first because it will take time for your bacteria, fungi, and worms to move in.

Some people complain that they see mushrooms growing in this potting soil and want a refund.

But that comes from a misunderstanding of how healthy soil functions and the role soil fungus plays.

If I see mushrooms growing around my garden, I pat myself on the back!

Final Thoughts

There is a significant price difference when it comes to Garden Soil and Topsoil.

But you get what you pay for!

While there’s no harm in building terraces or filling in ditches with Garden Soil, it would be rather a waste of money.

If you’ve got a large area to cover, you’re better off installing a layer of Topsoil and using Garden Soil in specific beds or planters.

Don’t forget to buy local whenever you can, and your soil will be more effective in your climate.