When it comes to your lawn, gardening, or landscaping projects it’s important to understand the differences between lawn soil and topsoil. These terms are often used interchangeably, the two soils are actually quite different and each performs an important role in a healthy lawn.
Lawn soil is composed of rocks, clay, and compacted dirt, whereas topsoil contains loose dirt, sand, healthy microbes, and organic matter.
Density and Nutritional Content
Lawn soil is significantly denser. Because topsoil is looser, it more easily absorbs nutrients and other benefits from the sun, air, and water.
The rocks, clay, and compacted dirt found in lawn soil make it dense and heavy. When attempting to establish new grass in your yard, lawn soil can limit growth and cause drainage issues. The rocks and clay, in particular, can impede drainage and slow grass growth.
Often sold in bulk, lawn soil is commonly used to fill large holes and level areas on commercial and residential properties.
The loose dirt and sand, along with healthy microbes and other organic materials in topsoil make it perfect for encouraging new root growth in lawns and gardens. Packed with its own nutrients the looser, lightweight lawn soil makes the benefits of water, sun, and air more available to grass and other plants. In addition, the sand typically found in topsoil helps promote filtration and water retention.
Topsoil is readily available at garden and home improvement stores.
When to Use Lawn Soil vs Topsoil
While both soil types are used in lawns and gardens, determining how much lawn soil and topsoil to use can be tricky – too much of either soil type can produce undesirable results. However, by combining the two soils in the right proportions, you can create the optimal environment for healthy grass, flowers, and shrubs.
Each soil type serves a specific purpose. Rocks and clay in typical lawn soil provide a solid foundation for a yard, but offer less than desirable conditions for growing new grass. In contrast, nutrient rick topsoil provides the environment new grass needs, yet excessive topsoil can also leave soft, uneven spots in the lawn leading to fungal growth, mold, and weeds.
Lawn Soil vs Topsoil: Commonly Used
- The general rule of thumb is to use topsoil for the top 3-6 inches of the lawn.
- Lawn soil is often used to fill large holes and level soil on commercial and residential properties.
Over time, topsoil naturally changes to lawn soil as it becomes saturated and compacted. If your existing soil is too compact or contains too much clay, topsoil can be mixed into the lawn soil as an amendment. This process aerates the soil and helps to cycle the nutrients.
Simply till compact soil until loose, then add a layer of topsoil and rake it into the existing lawn soil.
Spreading a thin layer of topsoil over your grass, known as topdressing, helps rejuvenate the lawn’s soil while allowing existing grass to continue growing. Topdressing can be done annually, especially in areas with clay or compact soil, but be careful, adding too much topsoil can cause root suffocation and drainage problems.
The soil under your lawn feeds your grass, shrubs and trees, and over time, important nutrients become depleted, affecting the health of your grass and other plants.
In addition, your soil’s pH level may become too acidic or too alkaline to support healthy growth. Testing your soil gives you detailed information, so you can feed your grass, shrubs and trees the balanced diet they need for optimum health.
Always test your soil before laying new sod or planting new trees or shrubs. For established lawns and landscapes, the rule of thumb is to test every two to three years before fertilizing in the spring.
Home testing kits are available at home and garden centers, but for a small fee, you can send soil samples through your local extension service for thorough testing and expert recommendations.