What is Soil profile:-
Soil profile may be defined as a vertical section of the soil from the ground surface downward to where the soil meets the underlying rock.
What is soil Horizon
Soil profile is made up of distinct horizontal layers, parallel to the surface. whose physical chemical and biological characteristics differ from the layer Above and beneath, is known as 'Horizons'.
A soil Horizon make up a distinct layer of soil having different properties and characteristics, and each layer tell us a story about the life of soil or process of soil formation.
Why do we study soil profile:-
1. Unit of study in pedological investigation. The soil profile is important tool for classification of soil which is the applicable for thorough understanding the soil.
2.It is an important tool for nutrient management, by examine the soil profile, soil fertility can be assessed.
3. The soil Horizons indicate the history of soil formation and are the result of Soil farming processes.
How do we study the soil profile :-
To study the soil profile, large area or landscape landscape is divided into into several smaller parts, that can be easily studied.
This smaller part of soil (smallest unit of land) surface can be used for the study of soil profile, is Called as" Pedon"
The pedon is three dimensional sample of of body of soil that is 1 to 10 metre square at the surface and extent to the bottom of soil.
And the group of similar Pedon on is known as PolyPedon, which is bounded form below by Bedrock (or not soil) and laterally by the Pedon of dissimilar characteristics.
Pedon include both vertical and horizontal extent of soil while soil profile include vertical extent of soil.
There are 5 master horizons in the side:-
- O – horizon = Organic layer.
- A – horizon = Mineral layer.
- A2/E – horizon = Eluvial layer.
- B – horizon = Illuvial layer.
- C – horizon = Unconsolidated layer / Zone of least weathering.
O – Horizon = Organic Soil layer:- Organic soil layer is present above the mineral soil layer. which is made up of partially or fully Decomposed plant and animal reduce. Usually occur in forest areas (virgin soil) And not found in arable land.
It is subdivided into two specific horizons:-
O1 layer:- consist of partially decomposed or undecomposed plant and animal residues, which can be recognised by the naked eye.
O2 layer:- consist of completely decomposed plant and animal residues.
A – Horizon = Mineral soil layer:- Topmost mineral soil layer at or near the surface and it is is subdivided into three parts:-
A1 (A):- uppermost mineral soil horizon, rich in organic matter, which imports dark colour as compared to the lower horizon.
A2 / E :- zone of eluviation or leaching or washing out of clay, iron and Aluminium oxide. Lighter colour compared to the upper horizon.
A3 / AB :- transition zone between A and B Horizons, having the properties more like those of A Horizons then B Horizons.
B – Horizon = Zone of illuviation or Accumulation or washing in of clay. iron and Aluminium oxide, and silicate clays From the above horizon and even from the below horizon in arid condition as calcium carbonate, calcium sulphate, and other salt during evaporation. This horizon is Sometime referred as the the sub-soil.
It is subdivided into three parts:-
B1 / BA :- Transition zone between A and B Horizons, having the properties more like those of B Horizons then A Horizons.
B2 :- zone maximum accumulation of clay, iron and Aluminium oxide.
B3/BC :- transition zone between B and C Horizons, having the properties more like those of B Horizons then C Horizons.
C – Horizon or Unconsolidated layer:- Under the solum, parent material, partially or fully weathered, outside the major biological activity and very little affected by solum forming process.
R – Horizon:- Consolidated Rock layer of Granite, Basalt etc. Under the Regolith.
What is Solum:-
Surface and subsurface soil layer that have undergo the some soil forming some processes. Solum is true soil. It include A, E and B or (A+B) horizon.
What is Regolith:-
Unconsolidated layer, above the Bedrock is called regolith, and it is produced by the weathering of Rock. It include A, E, B and C or (A+B+C) horizon.
Components of Regolith:-
most weathered:-Solum (A+B) or (A+E+B).
least weather:-Saprolite (C).
