What Is Topsoil and What Are Its Benefits? (2024)

The topsoil layer is where nutrients are delivered to plants, water is absorbed, sunlight helps to aid the growing process, and wildlife and microorganisms interact with the plant in various ways. In short, it is where the "magic" happens. Technically, topsoil is the top layer of soil in any garden or yard or field, usually referring to a depth of between 2 to 8 inches down.

This layer has the highest concentration of organic matter and microorganisms that provide essential support for plants to grow. Generally speaking, commercial topsoil is used to improve the nutrient density of soil in gardens and lawns since it is a balance of clay, silt, and sand.

When Adding Topsoil Can Benefit Your Garden

If you're lucky enough to be blessed with perfect topsoil, you're probably the envy of your gardening neighbors. But generally speaking, most soils benefit from added topsoil on occasion. Topsoil can wash away during rainy seasons or move around during construction projects. Too many weeds, foot traffic, or exposure to foreign substances can deplete its nutrients.

The practice of crop rotation is intended to benefit topsoil retention and prevent soil erosion or depletion of nutrients by changing the types of plants or crops grown every season.

If your flower or vegetable bed gets dried out or is exposed to organic matter that increases acidity (such as pine needles), adding fresh topsoil will improve its composition and raise the soil pH closer to neutral. To ensure optimal growing conditions, replenish topsoil as needed. Adding topsoil can improve drainage, enrich soil nutrients, and create better soil texture, making planting and weeding much easier.

How Does Topsoil Differ from Garden or Potting Soil?

Generally, topsoil is much heavier than potting soil. Soils sold commercially as garden or potting soils often have materials added to make them lightweight and fluffy in texture, such as vermiculite or peat moss. They can help lighten clay soils when mixed in, and they help grow plants in containers.

Some garden soils have extra organic matter added to give nutrients to food crops and flowers. Potting soils don't tend to hold together well in a garden bed because they're too lightweight to hold moisture effectively.

Types of Topsoil

Topsoil is usually described based on its texture and composition, which are affected by the minerals and materials the soil already contains naturally.

Often topsoil reflects the geological nature of its location. Soil types are also categorized based on the size of the particles they have, which directly relate to their texture. There are six main types of topsoil: clay, silt, sand, loam, chalk, and peat.

Clay

Some clay soils are so thick they're used for making clay pottery. This heavy type of soil stays wet and cold in winter but tends to dry out in summer. Clay soils are often lacking in proper aeration and drainage. They can become easily compacted and are hard to dig in. Clay soil usually needs amendments to make it suitable for gardening, but some vigorous plants tolerate clay without problems.

Silt

Silt is fine textured soil. It's normally light in color and retains moisture fairly well. It tends to have a neutral pH and be fairly rich in nutrients.

Sand

Sandy soil is light-colored. It's usually reasonably low in nutrients and lightweight. It can be useful to mix sandy soil into other heavier soils to get a good texture, but sandy soil can be prone to be washed or blown away easily, and erosion is a problem.

Loam

Loam combines sand, silt, and clay in a medium-textured mixture. It is a desirable soil, often rich in organic matter, with a good texture for planting and good drainage. It is dark in color and holds its shape when squeezed together. Loam is usually either mostly sandy or mostly clay.

Chalk

Chalky soil is light-colored, porous, and contains large amounts of limestone or calcium carbonate, making it highly alkaline.

Peat

Peat is lightweight and contains organic matter. It has excellent drainage. Peat soils don't occur naturally in many places, so peat is often harvested and exported for use in soil amendments and mixtures to improve garden soil's texture and drainage.

How to Apply Topsoil

You can acquire topsoil in various ways. Buying it in bulk can be a good and economical option for larger amounts. Some topsoils sold in bulk will have compost added. Or you can buy it in bags, usually weighing 20 to 40 lbs.

You can apply topsoil anytime, but most gardeners like to add it in spring before planting. In the fall, it may also be added as a top dressing that will allow nutrients to break down into the soil. You may add topsoil into plantings by adding to the holes where shrubs are planted. You may spread a layer of it over the garden before or after planting.

If the soil you purchase is somewhat lumpy, mix it in a wheelbarrow or on top of a tarp before spreading it in your garden. You can spread the soil by pouring it from containers or applying it with a shovel and then leveling it with a rake or a broom. Spraying down the layer of topsoil lightly with water after you spread it will help fix it in place.

When to Till Your Soil

Tilling means turning the soil, which helps to aerate the soil, controls weeds and insect activity, and prepares the soil for seeding. It's best to till a new gardenin the spring when the soil is dry, and the weather is becoming warm. Depending on your region and climate, it can be March to early June.

However, tilling may not be required every season; it's only essential if you notice that the soil is compacted. Strike a balance because too much soil tillage can increase the likelihood of soil erosion, bring buried weed seeds to the surface, and cause nutrients to leech out of the soil and drain into the waterways. Also, killing the beneficial insects in the soil works to the detriment of the soil's vitality. Instead of tilling, consider top dressing with compost instead.

How Often to Fertilize

Each plant has different nutrient requirements. Frequency varies and depends on the particular plant's care guidelines.

Nutrients can come in the form of fertilizer, compost, or planting in already-rich soil. Potassium is usually the biggest nutrient supporting flowering and fruiting plants. Plants like roses and hydrangeas are typically heavy feeders, needing feeding every two to four weeks, while some flowering plants like asters and coneflowers don't need any supplemental feeding.

Most plants that produce fruits and vegetables require a lot of nutrients to grow well and prolifically, so fertilize or enrich the soil on a schedule according to the plant you are growing. You can skip fertilizer and opt for high-quality compost or other supplements like fish emulsion or bone meal mixed in with your topsoil, depending on the nutrient needs of your plants.