Pedogenic or Soil Forming Processes For Competitive Exam

Soil Forming Processes

Pedogenic or Soil Forming Processes

It is the geological weathering produces weathered rock material i.e. the parent material and when the genetic factors set the stage for soil development.

The pedogenic processes change the parent material in to soil with varying horizonations.

The pedogenic processes are extremely complex and dynamic involving many chemical and biological reactions, and usually operate simultaneously in a given area.



Humification is the process of transformation (decomposition) of raw organic matter in to ‘HUMUS’.

It is an extremely complex process involving various organisms such as bacteria, fungi, actinomycetes, earth worms and termites.

The decomposition of organic matter takes place in two phases: mineralization and humification. Mineralization is a biochemical breakdown of dead plant tissues by soil microorganisms to produce simple structured soluble organic substances, mineral compounds, metal cations and gases (CO2). During the humification, soluble organic substances regroup themselves in to large molecules by polymerization and become poorly soluble. They form major part of soil humus and provide site for retention of cations. The other part of humus is the polysaccharides – gummy products of microbial excretions, which help in soil aggregation


Eluviation means “Washing out”. It is the process of removal of constituents in suspension or solution by the percolating water from the upper to lower layers.

The eluviation encompasses mobilization and translocation of mobile constituents resulting in textural differences.


The process of deposition of soil materials (removed from the eluvial horizon “E”) in the lower layer (or horizon of gains having the property of stabilizing translocated clay materials) is termed as “illuviation”.

The horizons formed by this process are termed as illuvial horizons (B-horizon especially). All these basic pedogenic processes, combine to result in a number of wide ranging soils that are observed on surface of the earth.


It is a process of soil formation resulting in the formation of podzols and podzolic soils.

It is the process of accumulation of silica and eluviation of sesquioxides.


In tropics, certain soils are massively impregnated with sesquioxides to the extent of 70 to 80 per cent of the total mass, and forms a cemented horizon, which when dried becomes very hard like a brick.

This soil forming process is called “laterization” or “lotozation” e.g. Soils of Malabar hills of Kerala.


The gleization is a process of soil formation resulting in the development of a glei (or gley) horizon in the lower part of the profile above the parent material due to poor drainage conditions or water logged conditions.

Such soils are called “hydromorphic soils”. This process is not particularly dependant on climate (high rainfall as in humid regions) but often on drainage conditions.


It is the process of accumulation of salts such as sulphates, chlorides of calcium, magnesium, sodium and potassium in soils in the form of salty (salic) horizon.

The soils are called saline soils, which have ESP less than 15 percent and pH between 7 and 8.5. CRainfall as in humid regions but often on drainage conditions.


The process involves the accumulation of sodium ions on the exchange complex of the clay to an extent of >15 per cent, resulting in the formation of sodic soils (solonetz) under arid and semi-arid conditions.

This occurs when anions like carbonates and bicarbonates predominate in soil.


This process refers to the removal of Na+ from exchange sites.

The Na+ can be eliminated by increasing the concentration of Ca2+ or Mg2+ in the water, followed by improved drainage facilities.

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