Did you know? There are many aspects that's important for a plant growth. One of them is soil structure. The arrangement and organization of the particles and compounds that make up soil is known as soil structure.

The various arrangement of the soil influences its ability to store and transport air, water, organic, and inorganic substances. It also affects plants growth and development.

Apart from the benefits for plant growth, soil structure takes a long time to form. It may take a hundred or even thousand years for one inch of soil to form. As it forms, it creates several layers that makes up the soil structure.

Six layers of the soil structure

1. O Horizon

The first or the top layer of soil structure is called the O horizon. O Horizon has at least 20% organic matter by mass. It is an organic layer of the soil, which is mostly made up of leaf litter and humus.

2. A Horizon

The next is A horizon which is also called the topsoil. It is located below O horizon and above E horizon. A horizon can be buried and no longer found in the surface if there are natural events such as flooding and volcanic eruption. This dark-colored layer is made up of humus and other mineral particles.

3. E Horizon

In contrast with A horizon, E horizon is light in color. It is located beneath the A horizon and above the B horizon. E horizons are usually found in forested areas. It is because of the higher precipitation and forest litter is acidic.

4. B Horizon

The B horizon is also called the subsoil. It is located beneath the E horizon and above the C horizon. There is an accumulation happening in B horizon known as illuviation. It accumulates clay, soluble salts, and/or iron.

5. C Horizon

The C horizon is also called the regolith; located beneath the B horizon and above R horizon. There is very little organic matter in this layer and plant roots do not penetrate into this layer.

6. R Horizon

The R horizon is the bedrock layer. It is located beneath all other layers. Bedrock layer is made up of igneous, sedimentary, or metamorphic rock.

Four types of soil structure

Not only layers, soil structure also has different types. The four main types of soil structure are columns, blocky, granular, and plate-like.

Some soils have a basic structure, with each unit being a single entity with no smaller units. Others have a compound structure, in which big units are made up of smaller units that are divided by weak planes.

1. Columns

When soil is shaped in blocks and the related cracks are typically longer in the vertical shape rather than the horizontal shape, it is classified as column-type soil.

Water penetration, drainage, and aeration are all good in the column soil structure. Found in dry areas, this type of soil usually has a salt cap.

2. Blocky

The size of the soil will be big with a blocky soil structure, and cracks will run vertically and horizontally. Blocky soil structure has good water penetration, while drainage and aeration are moderate. The size of the dirt blocks is generally between 1.5 and 5.0 centimetre.

3. Granular

The granular soil structure is similar to the blocky soil structure, except that the dirt is generally less than half a centimetre in diameter. The cracks are all the same size and go horizontally and vertically.

Although there is good water penetration, this is the best type of soil for drainage and aeration. The granular soil texture is prevalent when roots have developed in surface horizons.

4. Plate-like

In compacted soil, plate-like soil structure is common, with cracks that are stretched horizontally rather than vertically. Moderate water penetration, aeration, and drainage are all possible in a plate-like soil structure.

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