What Is The Difference Between Topsoil And Subsoil

You have probably heard or studied about the different soil layers in middle or high school. Back then, it was just mere information you should remember in class. But now that you’re enjoying gardening as your profession or a hobby, you must know the difference between the topmost soil layers: the topsoil and the subsoil.

If you need clarification on their similarities and differences, we’ll discuss them below.

The Different Layers of Soil

For a quick refresher, before we dive deep into each layer, there are three several layers of soil: the topsoil, the subsoil, and the bedrock. Soil is essential to plants and animal life because it provides the first link in the food chain for them. We’ll discuss them individually below. (Read Potassium Salts Of Fatty Acids Moss Control Guide)

What is Topsoil?

Topsoil is the topmost layer of soil in any garden, yard, or field. It has an excellent soil structure, and its usual depth is 2 to 8 inches down the ground. It’s typically considered the most productive and vital section of garden soil because it’s very rich in nutrients and organic matter.

When it comes to farming and gardening, topsoil makes a perfect choice. Not only do many plants thrive in it, but also some microorganisms, insects, and worms keep the soil enriched. Since it’s exposed to atmosphere and light, it is where life thrives, whether insects, organisms, or plants.

Different Kinds of Topsoil

Topsoil can be described based on its texture and varying amounts of composition. It comes in six different kinds:

Clay

Clay soil gets wet and cold during winter but dries out during summer. Very thick clay soil is usually used for making clay pottery because they are easily compacted. Some vigorous plants like Aster and Bearded iris grow fine in them but needs amendments most of the time so they can be fit for gardening.

Silt

A fine textured soil, silt is typically light-colored and can retain moisture well. Silt usually has neutral pH and is rich in nutrients, so countries like India use this in growing plants and fruits like tomatoes, sage, rose, daffodils, and peonies, among others.

Sand

Sand is usually low in nutrients. Because it’s lightweight, water and air easily wash or blow it away, so it’s often mixed with heavier soils to get a great texture. Erosion is also a problem when it comes to sandy soil.

Loam

Loam soil is a combination of clay, silt, and sand. Most gardeners and farm owners use this kind because it’s rich in organic matter, has good drainage, and has a fantastic texture that makes it perfect for planting.

Chalk

Light-colored, porous, chalky soil has enormous amounts of limestone or calcium carbonate, making it highly alkaline.

Peat

Peat is lightweight, contains organic matter, and has excellent drainage. It doesn’t occur naturally in most places, so people mainly harvest it for soil amendments and to improve its texture. (Read Best Time To Remove Pachysandra)

Characteristics of High-Quality Topsoil

Not all topsoils are the same. High-quality ones with good characteristics make them ideal for gardening and farming. Here are some properties you need to look out for when looking for high-quality topsoil:

Darker color

You will notice how different topsoil have different colors and tones. Go for the ones with darker shades- anything coffee-colored to almost black. Topsoil with rich and dark color indicates it is rich in organic matter. And when more organic material is present, it means more concentrated nutrients.

Loose texture

Apart from its color, try to hold the soil in your hand. If it crumbles easily and feels slightly gritty, it’s a good sign that it’s rich in organic matter. Topsoil that doesn’t easily crumble and forms into a clump usually has too much clay, which isn’t suitable for plant life.

Screening

Screened topsoil is better than unscreened because you’re guaranteed consistent particle size. Screened soil also allows better nutrient delivery and natural water movement throughout, which helps boost plant growth.

What is Subsoil?

Subsoil is the layer directly beneath the topsoil or surface soil, about eight inches deep. It is usually made of clay, muck, or loess with stores of trace elements necessary for plant health. Regarding soil fertility, it’s less fertile than topsoil since it has less humus and organic matter.

While subsoil may have less organic material, it’s supplemented by other vital minerals found only in this soil. These minerals play a huge part in helping plants to thrive, which is often gotten when water runs through the topsoil and carries it down to the subsoil. If the plants don’t get enough nutrients to support themselves from the topsoil, they will start digging their roots into the subsoil.

What is Subsoil Made of?

Subsoil usually contains small rocks and clay minerals. Its three major components are sand, silt, and clay. It might not be as good as topsoil for growing plants, but it’s a critical layer in the overall health of plants and soil. Not only does it support the topsoil, but it also absorbs and drains water for the plants to grow. Subsoil also helps in anchoring taller plants and trees from beneath the ground.

Properties of Subsoil

Here are the distinct features of subsoil:

Less organic matter

Subsoil has significantly less organic material and humus than topsoil. Since humus carries rich nutrient contents, having less amount of it also affects the nutrient contents of the soil.

Diverse color

If the topsoil has only one shade of brown, the subsoil comes in diverse colors. It even comes in a combination of colors, such as brown-yellow or brown-red. But take note that a good subsoil has brighter color, which indicates the effectiveness of its drainage.

Minerals

Subsoil may lack humus but is rich in minerals like iron, magnesium, and calcium. Roots benefit from this greatly when they venture below the topsoil. Referred to as surface runoff, it pertains to the transfer of minerals from the topsoil to the subsoil. (Read Grass Is Turning White – What To Do)

How to Maintain a Healthy Subsoil

You must also keep your subsoil healthy, not just the topsoil. Here are a few reminders you should do to keep it healthy:

Mix organic matter and other soil amendments into the topsoil.
DO NOT overfertilize.
Make sure you have a good surface growing condition.
Plant deep-rooted plants for better soil structure.
Do not compact your soil and avoid loading it heavily, especially when it’s still wet.
Feed the earthworms because they make the channels deep-rooted plants follow into the subsoil.

What is Bedrock?

Beneath the topsoil and subsoil and just outside the Earth’s crust is the bedrock layer. It can be anywhere between 7 and 150 feet deep, and organic materials and root nutrients do not occur this deep in the ground. It can, however, supply land with future soil components.

What is Humus?

Humus is an organic material produced from decaying plants and animal matter. It is rich in beneficial nutrients for plants to grow and thrive on. Typically, topsoil has larger amounts of humus than subsoil, making it more fertile.

Final Thoughts

In summary, top soil and subsoil are two different soil layers that differ in the richness of organic matter, how it looks, how it’s used, and its soil fertility. Although they are entirely different, both soil layers are beneficial to each other and won’t function well enough if they don’t co-exist.