Topsoil is a commercially produced material that can be used to supplement or replace difficult soil in gardens. Most topsoil blends contain between 2 and 10 percent organic materials, making them very nutrient-dense. If you find that your existing soil is making it difficult for plants to grow, try mixing topsoil in with the top 2 to 5 inches (5.1 to 12.7 centimeters) of earth. The topsoil can provide vital nutrients, balance pH levels and help control moisture and evaporation rates. Even experienced gardeners can turn to topsoil when the existing earth has been depleted by frequent planting [source: Whitcher].
One common problem with topsoil occurs when it's poured on top of existing soil without blending or mixing. This creates a water absorption barrier where the two soil types meet, which can lead to issues with drainage and over-watering. To remedy this, always mix in your topsoil with the existing dirt so that water can flow freely between the two.