The Layers and Importance of Soil

Types, Layers, Importance of Soil

The soil is made of disintegrated rock and humus. It takes hundreds of years for rocks to break down into particles small enough to form soil. Humus is formed by the decomposition of leaves, dead animals, or other organic materials. Thus, the development of soil takes between hundreds and thousands of years.

Types of soil

What are the types of soil? There are four types: sandy, silt, clay, and loam.

Sandy soil

This type of soil consists mainly of small rock particles. It is unsuitable for growing most plants because its capability to retain water is very low. Only plants that require very little water thrive in this type of soil. However, it is perfect for a drainage system.


This type of soil is made of rock particles that are smaller than the particles that make up sandy soil. It contains other mineral particles as well. It’s the best type of soil for growing plants because it can retain water well. It also drains well. It is mainly found near lakes, rivers, and other bodies of water.


This type of soil is made of the smallest rock particles that are tightly packed together. It has very good water storage capacity. It is sticky when wet and smooth when dry. Since it has very little or no space for air and doesn’t drain well, it is less suitable for growing plants.


Loam is a combination of silt, sand, and clay, and that makes it the most suitable soil for farming.

Layers of soil

Soil is divided into different layers, one sitting on top of the other – in an arrangement called soil horizons. There are six main soil horizons (or layers of soil):

The O-Horizon

This is the topmost layer of soil and is primarily composed of fresh soil, living organisms, and decaying organic material. It is black or brown in color because of its organic composition. Roots of most small vegetation go only as deep as this layer.

The A-Horizon

This layer lies under the O-Horizon and is called the topsoil. It is made of minerals and decaying organic material. For this reason, it can be gray in color. Seed germination and plant root growth take place in this layer. It can be distinguished by the different types of soil in it.

The E-Horizon

This is the layer beneath the A-Horizon. It is the thinnest layer and is lighter in color because of the leaching of minerals. It is depleted of minerals and organic compounds. For this reason, it also called the eluviation level and is mainly made of sand and silt after losing most of its minerals.

The B-Horizon

This layer is found under the E-Horizon and is known as the subsoil. Primarily made of clay, large rock, and bedrock, it also contains clay, iron, aluminum, and organic compounds. For this reason, it is also called the illuviation level. The roots of big trees go no further than this layer.

The C-Horizon

This layer lies under the B-Horizon and is called the regolith. It is made of fragmented pieces of rock and contains very little organic matter. Plant roots do not reach this layer.

The R-Horizon

This is the final layer of the soil and is known as the bedrock. It is made of solid rocks that include limestone, granite, and basalt. It is gray in color and is found 50 meters below the topsoil.

Importance of soil

The soil is important for many different reasons. Here are some of the examples of the importance of soil.

1. The soil is the medium for plant growth: Soil makes nutrients, minerals, moisture, and water available to plants. It supports their roots and helps them stay erect for growth. Without soil, there would be no plants. And, without plants, there would be no animals.

2. Soil provides habitat for animals, insects, and microorganisms: Soil provides habitats for animals, insects, and microorganisms that include ants, termites, worms, moles, and numerous types of bacteria. These living beings, in turn, enrich the soil through their actions.

3. Soil acts as a filter for surface water: Most of the rainwater seeps into the earth, which is made possible by the different layers of soil. As the water goes through the different layers, it gets filtered. As a result, the purest water is found in underground aquifers.

4. Soil helps maintain the balance of atmospheric gases: Soil serves as a carbon store. It contains twice as much carbon as the atmosphere. It also contains nitrogen and other gases in abundance. Thus, it helps maintain the balance of atmospheric gases.

Layers and Importance of Soil

The layers and importance of soil for plants and animals cannot be overstated. There would be no life on Earth without it.

At All American Environmental, we are your professional consulting and contracting environmental specialists. We specialize in soil testing, investigation, assessment, and remediation. Feel free to contact All American Environmental to learn more. Our office is located in Lake Hopatcong, NJ,