All contractors, landscapers, and gardeners use topsoil, but not all of them understand what it is or how it can be tested. Topsoil comes in many forms with various chemical compositions, so if you’re building an outdoor vegetable patch or digging a trench, it’s important to know how to identify and work with the earth beneath your feet.

Geologically speaking, topsoil is the dirt that covers the earth. It’s so named because it covers (or “tops”) subsoil and bedrock. Topsoil is nutrient-rich, made up of organic materials, microorganisms, trace minerals, oxygen, and water. Topsoil is therefore very important for gardening and harvesting healthy crops.

Topsoil differs from garden soil in that it doesn’t need to be explicitly used for planting. Where garden soil has the ideal mixture of fertilizer for planting, topsoil can have a range of textures. Landscapers and contractors should talk to their local washed gravel and dirt supplier to get an idea of what will be the best fit for their project. You can also perform a soil test to determine the types of topsoil in your own backyard.

There are several topsoil uses, but gardeners often look for a sandy loam–that is, 40% sand, 40% silt, and 20% clay. The acidity of the soil also determines what plants will grow there, so expert gardeners should have an idea of how alkaline the earth is.

Aside from gardening, some topsoil uses include improving the drainage of a grassy area or filling in bare spots on a lawn. Like drainage gravel, a sandy topsoil mixed with bark can create a base for excess water to drain. Of course, utility sand and sand for sand boxes also falls into the category of topsoil, meaning that your topsoil supplier should have it in bulk as well. These can be used for weights, garden design, and more.

When in doubt, talk to a supplier about the types of topsoil and how they are best used. They’ll be happy to provide you with the right material at the right price so that you can get your product underway.