9 Characteristics Clay Soil

Clay soil, called “heavy soil,” is a soft, moist soil composed of more than 30% clay, aluminum and iron.

After rain, clay soils, which absorb a lot of water, are flooded. On the other hand, in the dry season, this type of soil tends to form a hard, poorly aerated layer of soil, which makes the development of vegetation difficult.

Characteristics Clay Soil

  • Clay soil is less permeable and therefore has a greater capacity to store water.
  • It concentrates significant amounts of iron and aluminum oxides in its composition.
  • They are fertile and of good quality for the practice of agriculture.
  • It has a thin consistency.
  • It is made up of very small particles. Therefore, it becomes very compact when hydrated.
  • The earth from this type of soil is widely used for the manufacture of ceramics.
  • It has small and compact grains (micropores)
  • High waterproof
  • High concentration of nutrients
  • Low acidity
  • Suitable for cultivation and agricultural activity
  • More resistant to erosion

What is clay soil used for?


Whether in artistic, industrial or traditional ceramics, all a professional needs is just the ability to work with the right amount of water and with the help of a kiln with temperatures around 600°C.

Archaeological findings show that this art was already made in the period known as the Neolithic (around 8,000 years BC), and has reached our days with the ability to produce everything from floors and tiles, to pots, vases, pans and beautiful artworks.


According to archeology experts, the use of brick in construction is already 5,000 years old. These conclusions were based on the remains of objects found in archaeological sites in Asia Minor, Egypt , Palestine, China, Turkey, among other regions of the planet.

Already at that time, clay soil was collected from the banks of rivers, flooded forests or other wetlands that could provide this material.

The next steps are cleaning the collected product (to remove remains of straw, fibers, stones, gravel, etc.), kneading (binding) of the clay, modeling and drying in the sun (for at least 2 days), to finish with the cooking of the material in a wood oven (during the same period of time).

Bricks have been used for the construction of houses, buildings, walls, walls, partitions and endless other applications.


In order to have the real dimension of what a clay soil is, it is enough to remember that adobes (types of clay blocks made especially for masonry) were the “grandfathers” of the bricks that we know today.

Scientific research shows that at least 6,000 years ago they were already used as foundations for religious temples, catacombs, tombs of pharaohs, private residences, among other constructions where their incomparable resistance and impermeability could be taken advantage of.

Roof tiles

Clay tiles are considered one of the best ways to give an artistic look to a building.

Because they are resistant, waterproof, durable, absorb little of the sun’s rays, and even provide the building with an unparalleled rustic beauty, they have been used by the most diverse societies, in practically all times.

The tiles serve to cover and protect roofs, in addition to channeling and receiving rainwater, hail and snow.

The technique is practically the same as that used in the manufacture of bricks: a professional must know how to make the correct mixture between clay soil, water and other materials. The product must be modeled in molds, exposed to the sun and baked in a wood-burning oven for a few hours.

Types of clay soils

When talking about managing clay soils, it is important to keep in mind that there are different types of clay.

Clays can be of the 1:1 and 2:1 types, which have a series of completely different properties, which influence the agricultural suitability and the management adopted in clay soils.

1:1 clays are the most common, found in more eroded clay soils such as Latosol and Nitosol. The main 1:1 clay minerals are kaolinite, gibbsite, goethite and hematite.

These clays are so called because they are composed of clay minerals structurally organized in a layer of silicon tetrahedra followed by a layer of aluminum octahedra.

2:1 clays are less common, occurring only in some regions with specific climate conditions and soil material of origin, as is the case of the Campanha do Rio Grande do Sul region (in Brazil).

In this region, soils such as Chernozem and Vertisols are found, which have 2:1 clay minerals. Some of the main minerals in this type of clay are smectite and vermiculite.

2:1 clay minerals are so called because they have a structure made up of a layer of aluminum octahedra between two layers of silicon tetrahedra.

This structural arrangement allows water and nutrients to enter the intermediate layers, increasing the specific surface area and CTC (total exchange capacity) of the clay soil.

Therefore, soils with 2:1 clay minerals are recognized as having high base saturation and excellent natural fertility.

On the other hand, they are very plastic and sticky when wet and extremely hard when dry, which makes preparation operations difficult.

Thus, although a Vertisol is naturally fertile, it is difficult to manage because it offers a short period of time for machine input and soil preparation based on moisture.

Red land

Red earth is one of the main types of clay soil, with a reddish color, found in the states of São Paulo, Mato Grosso do Sul, Paraná, Santa Catarina, Rio Grande do Sul ; and also in Argentina..

It is considered very fertile (presence of several minerals), this type of soil is very suitable for the practice of agriculture, especially for the cultivation of coffee.


Many ancient people used clay (a type of modeling clay) as a raw material for the manufacture of utensils (vases, containers, pots), tiles, bricks, ceramics, art objects and ornaments.