Topsoil 101: Basic Composition and Function

holding a bit of topsoil

Topsoil is defined as the 2-8 inches of soil on the surface of the Earth. The reason why it is called ‘topsoil’ is because it is on the uppermost layer of the dirt that you work with when gardening or seeding. Subsoil, or the layer directly below topsoil, consists of hard-packed dirt and clay. It is largely unsuitable for anything organic except for large tree roots.

Topsoil is one of those things that every yard needs, but for some, they never really know what it is made of or how best to use it. Topsoil is the first line of defense for growing grass and plants, as well as fending off herbivore pests. Understanding the composition of topsoil, as well as what some of the best uses for it, is important to maintaining the health of your lawn and/or garden look its best.

The Components of Topsoil

Topsoil is an important part of any kind of lawn or garden because of its contents. Topsoil has high amounts of organic matter as well as microorganisms. As plants, vegetables, and other organic matter dies, it slowly decays, and the nutrients are returned to the topsoil from where it came. Microorganisms, as well as organic matter, can help greatly with growing and keeping out bacteria that may cause issues with plants.

Other elements of topsoil include sand, manure of various types and very small pieces of rock and stone. Its composition varies based on location, for topsoil is not the same everywhere.

Topsoil can be found at your local gardening center. Often, topsoil can be purchased as a mix of sand, silt, and clay. The difference between the topsoil that you will find at your home is that the topsoil at the gardening centers gives you the exact percentages of what you can find in each bag of topsoil.

When just using the topsoil around your home, often the components are in the incorrect proportions. So, dig up some of your topsoil and test it to see what percentage of the different components already exists in your soil. It is as simple as going to your local hardware store, finding a soil test kit, and following the instructions. Often you will be instructed to dig a small hole in the parts of your yard that you are planning on testing, and then the kit will determine the pH balance of your soil. Knowing what kind of soil you already have will help you figure out what kind of topsoil to purchase at your local garden center for more conducive planting.

How to Use Topsoil

Topsoil is best used in your yard to allow nature to do the heavy-lifting for you. In other words, a high-quality topsoil composition is what you need to encourage healthy growth for plants, trees, vegetables, fruits, and shrubbery. Topsoil can also prevent weeds and pests from infecting your plants.

Using store-bought topsoil can protect bulbs and root systems, as well as the buds still growing underneath the soil. Topsoil is much less expensive than garden soil, which is usually richer in nutrients. So, when you use the topsoil, you can use it more freely than other soils.

Topsoil often comes in larger bags, so make sure that you are getting the right kind before you purchase. Otherwise, you may have a large bag of something that will just sit in the back of your garage or shed.

Topsoil can be a bad idea when you want something to blanket your entire yard or gardening area. It is made to be used in large chunks but is supposed to work with your yard rather than be a replacement for it. The naturally occurring topsoil under your feet has come from millions of years of the Earth trying to figure out what works best, so trying to use all store- bought topsoil that isn’t a native composition to your yard for is probably not a good choice. Topsoil is there to enhance what is already there or to help plants struggling to grow due to an incorrect balance. So, when making use of topsoil make sure that it used correctly and sparingly.