Characteristics of different types of Soil

 

Soil

The term soil has different interpretation among the scientists and the soil engineers. For soil scientists anything which is capable of growing plants and crops is known as soil. For geologists the soil is actually product of physical, biological, chemical deterioration of rocks or weather bedrocks and is developed by the effect of weathering. 

It’s obvious that the soil is an abiotic factor and very important to the life on earth. When organic matter decomposes, it constitutes the soils and helps in the growth of the plants. Soil is the main source of nutrition for plans. It also anchors the plants. The Fauna and Flora is diversified on the basis of the type of soil.

Some of the rocks breakdown into smaller particles which ultimately forms the soil particles. And after this Peds are formed, when the smaller particles of the soil aggregate. Soil structure is the next which is formed, when the Peds join together with each other, results in the soil structure.

   

Formation of soil

Break down of rocks also known as weathering of rocks plays a crucial part in the development of soils. The Weathering is Chemical or mechanical or it may be biological.

1. Chemical Weathering:

In this process chemical causes the breakdown of rocks by changing the chemical composition of rocks. Some minerals changes to another one, and the size of rock reduced.

2. Mechanical Weathering:

This is the process of mechanically breakdown of the rock into smaller one; temperature plays an important role in this process. High temperature causes the expansion and low temperature causes the contraction, this effect break down the rocks.

3. Biological Weathering:

When living organisms causes the deterioration of rocks this process is known as biological weathering.

Animals and plants are the key player, they dwell into the rock and plants can penetrate in the rocks thus piercing the rocks into smaller pieces.

Types of Soil

As the soil is formed by the breakdown of the rocks so it has different particle size, it has different chemical composition, thus all these particles constitute the soil, and properties of soil also depend on these things.

On the basis of size of particles the soil is classified as

·         Clay

·         Sandy

·         Silty

·         Peaty

·         Chalky

·         Loamy

And on the basis of Climate it is divided into two major groups

Ø  Pedocal Soil

Ø  Pedalfer Soil

·   Laterite Soil

Pedocal Soil

It is the type of zonal soil, which is characterized by large amount of CaCO₃ and CaO, and low amount of organic matter, this is where the name is derived Pedocal, these are very common in the areas where the rate of evaporation is more than the rate of leaching, also called semiarid regions. They usually deposited in the A horizon of the ABC soils.

Usually grasses and brushes are common in such kind of soils. It is observed that the annual rain fall in Pedocal soil is areas is less than 65cm, so by such a low amount of rain obviously there will be less chemical weathering and, and organic material found there will also be in low amounts. Soils in this type are slightly less fertile.  They are lightgrey-brown in color. These are usually alkaline soils.

Pedalfer Soil

This type of soil is rich in Aluminum and Iron oxides. As name suggests Ped (soil), Al-(Aluminum), and Fer-(Ferrum). These are common in humid regions and forms B horizon of the ABC soil type.

Rainfall above 65cm is required for this type of soils. Weathering is more in such areas, thus more chemical reactions. It supports the faster plant growth and forms forests, mostly deciduous trees which shed off their leaves annually are found in pedalfer soils. These soils due to high organic and chemical weathering and clay content are fertile in nature. Pedalfer soil is acidic in nature, and is highly leaching.

Laterite Soil

Laterite derived from a Latin word which mean brick. It is a kind of soil which is humid and hot. It is regarded as special type of Pedocal soil. The tropical rainforests where the rain literate everyday dissolves the nutrients and thus results in the low nutrient content.

Laterite soil is very thick but not very fertile in nature. There is intense chemical weathering and practically no humus at all. Intense rainfall removes all the soluble minerals and deprives the plants and soil from nutrients. And those which are less soluble like aluminum and Iron Oxides are left behind, which makes the soil less fertile. Due to the presence of Fe₂O₃, these are red in color and hard.

Types of Soil on the Basis of Particle Size

a.   Clay Soil

      Clay is the naturally occurring aluminum silicate. It has smallest particle size amongst all the other types.

When dry it’s too hard and smooth but sticky in nature when wet. The size of clay particle is ≤ 0.002mm.

Due to such a smaller size the clay particles has the tendency to settle together and little spaces left between them, thus a little air can pass through them. It holds the plants tightly and provide immense amount of nutrients to the plants. Clay soils warms up too slowly. If it suffers drought it can form cracks and crusts, thus preventing plants to deep rooting for the quest of water.

b. Sandy Soil

       These soil particles are the largest in size. The particle of sand is also known as grain. The size is ranging from 2mm up to 64mm. It cannot hold water because there is lager space between the particles. It usually dry and gritty in nature. Due to minimum water withholding capacity, water drain more rapidly from the roots.

Plants in the sandy soil are not capable of using the nutrients effectively. The sandy soil is much warmer during the spring or summer seasons. Wet sandy soils do not form a ball in the hands; it crumbles through fingers very easily. So the sandy soil is not among the best soil types.

Silty Soil

The particle size of silt is larger than clay but much smaller than sandy. Silty soil particle size is ranging between 0.0039mm to 0.625mm. When gets wet it looks like soapy slick, hence smooth to touch. Usually when rolling into the hands, some dirt left on to the fingers. Silty soil is considered among the most fertile soils, due to retention of water for longer time and nutrients too. It is cold and drains slowly, due to retention capacity of water. Silt is mostly found in the rivers and estuaries.

Peaty Soil

These are usually organic matter and very fertile type of soil. Have bigger particle size than silty and clay soils. Peaty soil color is dark black or blackish brown. It has high water content, due to this property it is soft and easily compressible, and the organic matter is high in quantity. The humid (Peaty) soil begun to develop in some 9000 years ago, due to fast melting of the glaciers. This melting causes the death of the plants and thus increases the organic matter in the soil results in the peaty soil. It has the large ability to hold water even during the summer; if it gets dried it would be a great threat, to act as precursor for the fire.

Chalky Soil

It also contains the calcium carbonate or the lime. So these are very alkaline type of soil, have pH ranging from 7.1 up to 8.0. These soils are usually shallow, stony and free drainage. There is little organic matter is present in this type of soil thus making chalky soil less fertile. Only those plants which strive for alkalinity are the best option for this kind of soil.

Loamy Soil

Loam is a soil type which consists of Sandy, silty and also little quantity of clay and good quantity of humus. If we look for percentage of composition, it has Sandy and silty 40% each, and clay around 20%. Loamy soil is fertile and well drained and easy to work on. It can be further classified into sandy loam, clay loam, and silty loam, depending upon the concentration and cultivation characteristics. The pH is lighter and calcium levels are also not much higher due to organic matter. Loam is dark in color, meaty soft, and crumbled while treating with hands.

Ideal Type of Soil:

What we have discussed so far, it is obvious that the Loamy Soil is the ideal type of soil. Because it is the mixture of the Sandy, Clay and silty. It also has humus and large quantity of organic matter which is good for the nourishment of the plants. It also has the ideal capacity of holding water and drainage capacity is also optimal, thus makes the Loamy soil much fertile.