Topsoil vs Subsoil
Whether you’re sprucing up your garden on a weekend or diving into your first gardening project that needs that extra bit of research, understanding the soil type you’re working with is crucial. Whilst most people will think that garden soil is just a bit of dirt, it’s so much more than that – using the wrong type of soil can impact plant growth, lead to waterlogging and a lack of nutrients in your flower beds.
In this gardener’s guide, we’ll explore the difference between topsoil and subsoil as knowing how these layers work will not only boost your gardening knowledge, but also make your landscaping project that little bit easier!
What is Topsoil?
Topsoil is the upper layer of soil (typically 5 – 10 inches or 10 to 25cm deep) that contains most of the ground’s nutrients and fertility. Formed over a long period of time, topsoil is dark in colour, rich in essential nutrients and organic matter that most plants, vegetables and turf need to thrive, including nitrogen, phosphorus, potassium, and magnesium. This makes topsoil incredibly fertile and perfect for growing everything from lush flowers to your favourite veggies.
What is Subsoil?
Lighter in colour and just beneath the topsoil, you’ll find the subsoil. Similar to topsoil, subsoil consists of a mix of small particles like sand, silt and clay, but it contains far less organic material. Subsoil serves as an anchor within the earth, offering important drainage and acting as a foundation for the roots of trees and shrubs.to grow. Therefore, it’s important for subsoil to have the right balance of materials to allow water to flow effectively.
Key Differences Between Topsoil and Subsoil
Understanding the differences between these two soil types can make a big difference in your garden, so we’ve made an easy list for you to understand!
Nutrient Content
Topsoil is by far the better choice when it comes to nutrients. It’s where your plants get most of their food, so it’s important to have a high-quality topsoil! Subsoil, however, plays a supportive role, lacking in nutrients but crucial for structural purposes and allowing for proper drainage.
Texture and Composition
Topsoil is darker and looser, allowing roots to spread out easily and water to drain efficiently. Subsoil is lighter and denser, which helps prevent the soil above it from becoming waterlogged – ideally, a blend of premium topsoil and a multi-purpose subsoil is best!
Colour Variations
You’ll notice that topsoil is generally darker in colour because it’s rich in organic materials, whereas subsoil tends to be lighter, with variations depending on the local geology and soil structure.
Role in Plant Growth
While your plants live and feed in the topsoil, they rely on the subsoil for foundational support, making both layers absolutely necessary for a range of gardening projects such as a vegetable patch, laying new turf or filling in slopes!
Microorganisms and Life
Topsoil is more conducive to supporting living insects because it is directly exposed to the atmosphere and consists of small, loose particles. This structure allows creatures like earthworms, centipedes, millipedes, and other insects to thrive and make their homes in the topsoil. Subsoil tends to be more compact than topsoil, since it does not hold any air in the soil, therefore, any living insect cannot typically survive in this layer.
To Summarise…
As a new gardener, recognising the importance of both topsoil and subsoil will set your garden up for the long run. These soil layers work together in your garden’s ecosystem, each playing a critical role that supports lush, vibrant plant growth. By nurturing both, you’ll ensure that your garden not only looks beautiful but is also sustainable and healthy!
If you’re looking to improve your garden or thinking about starting a new project, Alsoils+ can provide the topsoil and subsoil you need. Working with both domestic and trade customers for the past 35 years, you can be sure we will deliver a high-quality service!
