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What is Topsoil?

A quick guide to the basics of topsoil and what kind of topsoil is appropriate for gardening.

Topsoil is the outer layer of the earth’s surface and is usually 5-30cm in depth. It is comprised of the three main groups of organic matter – these are humus, clay particles and sand. Good quality topsoil is comprised of a number of different things that enable it to help organic growth on the earth’s surface.

Topsoil can contain, among other things, organic matter, micro-organisms and worms, all of which help give topsoil the nutrients that will help your plants or vegetables thrive. A good, strong, healthy topsoil will also contain such living organisms as nematodes, insects, spiders, fungi and bacteria. All of these, plus the general organic matter such as droppings and rotting vegetation, go to making quality topsoil.

Most of the plants on the earth’s surface tend not to have roots that grow any further down than the base of the topsoil layer as they can get all the nutrients they need from within it. Topsoil can vary in colour, content and texture and it is important when gardening to work out what kind of topsoil you have, in order to assess how good it will be for growing your required plants or vegetables.

What is good gardening topsoil?

It is often recommended that the topsoil you choose for gardening should be a ‘loamy type’ because it has the right balance of sand, silt and clay for plants. Essentially due to this balance in the topsoil, the plants find it easier to draw the nutrients they need. Loam topsoil also means you will have to water less and it will give you quality plants – this is because the topsoil retains water and has excellent drainage.

What is loam?

Loam is not strictly a soil of its own. Loam is made up of the other three main types of soil:

Silt – which is made of quartz and has a smooth kind of texture
Sand – made from the small particles of rocks and minerals and has an ability to drain well
Clay – very nutrient rich but it can be difficult to work with

Topsoil Texture

When using the word texture to describe topsoil, it is in reference to the percentages of sand, silt and clay that are present in the topsoil. A good quality topsoil will have a balance of all three of these in order for the plant life to obtain the required nutrients and thrive in you garden. Generally speaking, a good quality topsoil will have less than 30% clay, less than 70% sand and less than 70% silt. Ensuring the right balance in your topsoil will give your plants the opportunity to thrive.

Why should I pay for topsoil?

A good quality topsoil is always going to be preferable to most soil you will find in your garden. Therefore, if you want your garden plants or vegetable to thrive then good quality is essential. If you want beautiful plants it is worth investing in the best topsoil you can afford; likewise if you are growing your own vegetables, you are going to want quality topsoil to provide you with the best results.