Topsoil

The uppermost layer of soil which is the main growing medium for grass roots. A topsoil (often referred to as the 'A' soil horizon) is usually darker in colour than a subsoil (often referred to as the 'B' soil horizon) due to increased biological activity, having a higher nutrient content, and also usually better soil aeration and better drainage capability. On specially constructed turf surfaces, such as a sports pitch, the imported topsoil material is normally referred to as a rootzone. This is because it will have been specified in detail and will be different from a natural topsoil.