Describe in brief about horizons of soil
Answers
Answer:
A layer of soil , Approximately parallel to the surface , having distinct characteristics produced by soil forming process is called horizons of soil
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. The different layers of soil are:
Topsoil
Subsoil
Parent rock
Each layer of soil has distinct characteristics.
Soil profile helps in determining the role of the soil as well. It helps one to differentiate the given sample of soil from other soil samples based on factors like its colour, texture, structure, and thickness, as well as its chemical composition.
Also refer: Minerals In The Soil And Soil Pollution
Read on to explore what is soil profile and the different layers of soil that make up the soil profile.
Layers of Soil
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.
The 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.
The 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.
In this layer, the seed germination takes place and new roots are produced which grows into a new plant. This layer consists of microorganisms such as earthworms, fungi, bacteria, etc.
The E-Horizon
This layer is composed of nutrients leached from the O and A horizons. This layer is more common in forested areas and has lower clay content.
The 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.
this layer holds enough water than the topsoil and is lighter brown due to the presence of clay soil. The soil of horizon-A and horizon-B is often mixed while ploughing the fields.
The 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.
The R-Horizon
It is a compacted and cemented layer. Different types of rocks such as granite, basalt and limestone are found here.
Also Refer: What Is Soil?
Types Of Soil Moisture
The different types of water present in the soil include:
Gravitational Water
The water that reaches the water table of the soil due to the gravitational force is referred to as gravitational water. This is not available to the plants.
Hygroscopic Water
This water is also not available to the plants. It is a thin film of water tightly held by the soil particles.
Chemically Combined Water
The chemical compounds present in the soil particles contain water. This is known as chemically combined water. This is also not available to the plants.
Capillary Water
This water is available to the plants for absorption. This water exists between soil particles in small capillaries.
Atmospheric Humidity
The hanging roots of the epiphytes absorb the moisture in the air due to the presence of hygroscopic hairs and spongy velamen tissues.
Also Read: Types of Soil
Importance Of Soil Moisture Content
Soil water carries food nutrients for the growth of plants
Soil moisture content determines the yield of the crop in a region
Crucial in maintaining soil’s temperature
Soil moisture acts as nutrients
Important for soil formation
Moist soil is ideal for the growth of many plants that demand a huge supply of water (Ex: Rice)
Soil moisture catalyses biological activities of microbes in the soil.
Water is a primary need for photosynthesis in plants.
Measuring Soil Moisture
The soil moisture can be measured by various tools mentioned below:
Tensiometers
These measures the tension of soil moisture. They are water-filled tubes, with a porous ceramic tip at the bottom. These are sealed and have a vacuum gauge at the top. They are inserted in the soil to the depth of the plant root zone. The readings obtained in the tensiometers indicate the availability of water in the soil.
Time Domain Reflectometry (TDR)
TDR – Time Domain Reflectometry is used to determine the soil moisture content. Steel rods are placed in the soil and electrical signals are sent through them. The returned signals are measured to determine soil water content.