Basic Introduction To Soil

Definition of Soil:

The uppermost unconsolidated part of the earth in which plants grow or a black or dark brown material  typically consisting of a mixture of organic remains, clay, and rock particles.

Types of Soil:

The following are some types of soils which are found all around the world.

• Sandy Soil: Sandy Soil is light, warm, dry, and tends to be acidic and low in nutrients. Sandy soils are often known as light soils due to their high proportion of sand and little clay (clay weighs more than sand).

• Clay Soil: Clay Soil is a heavy soil type that benefits from high nutrients. Clay soils remain wet and cold in winter and dry out in summer.

• Silt Soil: Silt Soil is light and moisture-retentive soil type with a high fertility rating. As silt soils comprised of medium-sized particles they are well-drained and hold moisture well.

• Peat Soil: Peat soil is high in organic matter and retains a large amount of moisture.

  This type of soil is very rarely found in a garden and often imported into a garden to provide an optimum soil base for planting.

• Chalk Soil: Chalk soil can be either light or heavy but always highly alkaline due to the calcium carbonate or lime within its structure.

• Loam Soil: Loam soil is a mixture of sand, silt and clay that are combined to avoid the negative effects of each type.

Similarly, the above-mentioned soils have composites of each other.

                       

Soil Profile: 

The soil profile is defined as the vertical section of the soil from the ground surface downwards to where the soil meets the underlying rocks.

The soil profile is composed of a series of horizons or layers of soil stacked one on top of the other. These layers or horizons are represented by letters O, A, E, C, B and R.

O Horizon:

The O horizon is the upper layer of the topsoil which is mainly composed of organic materials such as dried leaves, grasses, dead leaves, small rocks, twigs, surface organisms, fallen trees, and other decomposed organic matter. This horizon of soil is often black brown or dark brown in colour and this is mainly because of the presence of organic content.

A Horizon or Topsoil:

This layer is rich in organic material and is known as the humus layer. This layer consists of both organic matter and other decomposed materials. The topsoil is soft and porous to hold enough air and water.

B Horizon or Subsoil:

It is the subsurface horizon, present just below the topsoil and above the bedrock. It is comparatively harder and compact than topsoil. It contains less humus, soluble minerals, and organic matter. It is a site of deposition of certain minerals and metal salts such as iron oxide.

C Horizon or Saprolite:

This layer is devoid of any organic matter and is made up of broken bedrock. This layer is also known as saprolite. The geological material present in this zone is cemented.

R Horizon:

It is a compacted and cemented layer. Different types of rocks such as granite, basalt and limestone are found here.