Ultimate guide to topsoil

Topsoil is essential to any gardening or landscaping project. A good topsoil will help plants grow and ensure a garden looks the part.

Let’s unearth how to give your customers a great garden by understanding all the key things to know.

What is topsoil?

Topsoil is the uppermost layer of the earth’s surface, usually the top 5 to 20 centimetres of soil. It’s formed over many years through weathering, erosion and other biological activities.

Wind and rain break rocks into smaller pieces, and these particles are carried away and deposited in a new location. As plants grow and die, their leaves and roots collect on the soil. Bacteria, fungi and earthworms break down the organic material, enriching the soil with nutrients.

The result is soil packed with organic matter, nutrients and minerals, which is excellent for plant growth.

What is topsoil used for?

Topsoil contains all the nutrients needed for plants to thrive, so it is widely used in gardening and landscaping.

It’s better than regular potting soil, as it helps improve soil quality and is suitable for levelling uneven lawn surfaces. Topsoil has good water retention, helps with drainage and allows organic matter to decompose and improve soil structure.

Types of topsoil

There are several types of topsoil, each with its characteristics and benefits for various landscaping and gardening projects.

Sandy – contains large, coarse particles suitable for drainage and aeration. Used in construction projects and as a base for lawns.
Clay – is made up of fine particles that retain water and nutrients. Used for building foundations, but can become waterlogged and compacted if used for planting.
Loam – a mixture of sand, silt, and clay, and considered the ideal topsoil for plants. It has good drainage, water retention, and aeration, often used for gardening and crops.
Chalk – has a high concentration of calcium carbonate, which can make it unsuitable for some plants. However, some crops benefit from this nutrient-rich and well-draining soil.
Peat – is made up of decomposed plant material, high in organic matter and nutrients. Mainly used in horticulture and growing vegetables, as it may be too acidic for some plants.

The type of topsoil you choose depends on your project needs and how your customer will use their outdoor space. We’ll cover how to pick the suitable topsoil later in this guide.

Topsoil vs potting soil

Topsoil is different from regular garden or potting soil. These soil types often have extra items to make them soft and fluffy. They help grow container plants but don’t hold together well in garden beds. This is because potting soil is too lightweight to retain moisture effectively.

How much does topsoil cost?

Topsoil prices vary depending on the quality, quantity, and the supplier’s location. You’ll also have to consider delivery costs, especially when ordering a large amount of topsoil.

Topsoil is usually measured in tonnes or litres, at roughly 900 litres to one tonne. Measuring the space is essential to avoid overspending and wasting topsoil. Soil calculators then help determine how much topsoil you’ll need.

Benefits of topsoil

As a landscape gardener, incorporating topsoil in your projects ensures that your customers’ gardens are beautiful and functional. Some benefits of topsoil include

Provides nutrients – Topsoil is rich in nutrients, providing nitrogen, phosphorus, and potassium to nearby plants. It also helps extra oxygen reach plant roots. Using topsoil in garden beds gives plants a fertile area to thrive.
Improves drainage – Topsoil improves the drainage of garden beds, preventing waterlogging. This is helpful for areas with heavy rainfall and plants prone to root rot.
Retains moisture – Topsoil also helps retain moisture, ensuring plants have access to the water needed to grow and preventing soil erosion. This quality is beneficial during warmer months or drought periods.
Supports microorganisms – Topsoil contains many microorganisms crucial to soil health. Bacteria and fungi help break down organic matter, release vital nutrients, and improve soil structure.
Neater appearance – Covering garden beds with a layer of topsoil keeps them smooth, even, and tidy.

How to choose the right topsoil

With several types of topsoil available, choosing the right one can be challenging for a beginner landscape gardener. Picking the best topsoil for your project ensures your customer enjoys thriving plants and a healthy garden.

Here are some tips on how to choose the right topsoil.

Look at what’s there

Look at the type and quality of the existing soil, analysing the pH level, texture, and nutrient content. You’ll want to pick a topsoil that complements and enhances the current soil. If the current soil is heavy, you’ll want to choose lighter topsoil. If your soil is sandy, choose topsoil that retains moisture.

Outline project needs

Chat with your customer to find out how they will use the garden.

Fruit and vegetables like a healthy amount of organic matter, while acid-loving plants will benefit from a slightly acidic topsoil. Screened topsoil (sieved to remove larger debris) is better if they want a more even surface.

Loam soil is a good choice for plants requiring heavy watering and aeration, ideal for beds and borders. However, a silt-based mixture is recommended for levelling a lawn or preparing the ground to lay new turf. This soil type is lighter, easier to move and offers good drainage.

Research suppliers

Only buy topsoil from a reputable supplier, ensuring it's certified and free from contaminants, such as heavy metals and pesticides. Official soil certifications indicate the topsoil has been properly tested and meets quality standards.

Look for organic matter

Organic matter is essential for soil fertility and plant growth. Choose high-quality topsoil with a large percentage of composed materials, manure or leaf litter. If you’re not really sure what topsoil to use, speak with an experienced gardening professional. They can assist you in choosing the best type of topsoil depending on your customer’s gardening goals, climate, and soil conditions.

How to use topsoil

It’s best to apply topsoil in the spring or autumn so the nutrients have time to break down into the soil. While most gardeners prefer to apply topsoil before planting, you can add topsoil to garden beds by filling in the holes where shrubs are planted. Spreading a layer of topsoil over the garden before or after planting is also OK.

Before applying your topsoil, you should use landscaping tools to prep the area by removing weeds and debris and breaking down compacted topsoil. This will help create a smooth surface for the topsoil.

Add the topsoil by spreading it evenly across the garden bed. Use a rake or shovel to distribute it, taking care not to overload the soil, as this can create drainage problems.

A garden fork or tiler helps to mix the topsoil with the existing soil, ensuring that nutrients are evenly distributed.

Once the topsoil has been spread and incorporated, you can begin planting the garden. Advise the customer to water the plants thoroughly during the first few weeks to help them establish.

How to level a lawn with topsoil

You may also wonder how to apply topsoil over an existing lawn. This process is known as levelling and helps make a garden neat.

First, find any low spots. These may be areas that are sunken or have poor drainage. Mowing the grass and removing debris can make these spots easier to see.

Spread the topsoil over the low garden, focusing on those low points. Use a garden rake to smooth the soil and create an even surface.

Watering the newly laid soil helps it settle and compact, further levelling it.

Once the topsoil has settled, you can reseed the lawn to fill bare patches. For best results, use a fertiliser designed to promote lawn growth.

To help establish the soil and encourage growth, homeowners must regularly water the newly levelled garden during the first few weeks. Watering helps the grass roots grow deep under the surface and create an even lawn.

How much topsoil do I need?

To work out how much topsoil you need, measure the dimensions of the area you wish to cover and multiply this by the required depth.

A good rule of thumb is to add a layer of topsoil around 3–6 inches deep. This gives the turf and plants enough soil to root in.

One tonne of topsoil will generally cover around 22 cubic feet, 0.63 cubic metres, or 0.81 cubic yards. You can use this to determine how many bags of topsoil you need for your project. Online topsoil calculators can also work this out for you based on the area and depth you enter.

How to improve topsoil quality

Better quality topsoil helps plants grow and keeps gardens looking neat.

Before finishing your landscaping project, you should advise your customers on the best ways to look after and improve their topsoil so that they can enjoy the benefits for longer.

Add compost – Over time, the organic matter in the topsoil may decline. Homeowners can boost soil nutrients by adding compost and distributing it evenly across the garden.
Crop rotation – Encourage your customers to practice crop rotation, which involves planting crops in different locations in the garden each year. This prevents nutrient depletion, breaks the disease and pest infestation cycle, and ensures the soil stays healthy.
Use natural fertilisers – Overuse of synthetic fertilisers can harm the soil and reduce its quality. Suggest your customers use compost tea or bone meal instead.
Grow cover crops – Cover crops protect the soil from erosion and add organic matter to the soil when turned over. Examples include clover or rye.
Use mulch – Mulch helps soil retain moisture, keeps it cool, and prevents weed growth. It will also add organic matter back into the soil as it decomposes.
Avoid soil compaction – Compacted soil stops plants from growing and reduces the soil structure. To prevent this, homeowners should keep tiling or overturning to a minimum.

You’ll hopefully now have a good understanding of topsoil, including the different types, its benefits, how to use it, choose the right one, and maintenance advice.

Topsoil is integral to most landscaping projects, so knowledge is crucial before starting a new job.