Basic/Fundamental process

A. Fundamental Soil Forming Processes

•  It refers specifically to a particular cemented horizon in certain soils which when dried, become very hard, like a brick.

• Such soils (in tropics) when massively mixed with sesquioxides (iron and aluminium oxides) to an extent of 70 to 80 per cent of the total mass, are called laterites or latosols (Oxisols).

• The soil forming process is called Laterization or Latozation.

• Laterization is the process that removes silica, instead of sesquioxides from the upper layers and thereby leaving sesquioxides to concentrate in the solum. The process operates under the following conditions.

i) Climate:  Unlike podzolization, the process of laterization operates most favorable in warm and humid (tropical) climate with 2000 to 2500 mm rainfall and continuous high temperature (25°C) throughout the year.

ii) Natural vegetation: The rain forests of tropical areas are favorable for the process.

iii) Parent Material: Basic parent materials having sufficient iron bearing ferromagnesian minerals (Pyroxene, amphiboles, biotite and chlorite), which on weathering release iron that are congenial for the development of laterites. 

In the process of decomposition of organic matter various organic acids are produced. The organic acids thus formed act with Sesquioxide and the remaining clay minerals, forming organic- sesquioxide and organic clay complexes, which are soluble and move with the percolating water to the lower horizons.

As iron and aluminium are removed, the A horizon gives a bleached grey or ashy appearance. The Russians used the term Podzols (pod means under, the zola means ash like i.e. ash-like horizon appearing beneath the surface horizon) for such soils.

To conclude, the Podzolization is a soil forming process which prevails in a cold and humid climate where coniferous and acid forming vegetations dominate. The humus and Sesquioxide become mobile and leached out from the upper horizon s and deposited in the lower horizon

Eluviation:

v  It is the mobilization and translocation of certain constituents viz., Clay, Fe2O3, Al2O3, SiO2, humus, CaCO3, other salts etc. from one point of soil body to another.

v  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.

v  The eluviation process involves mobilization and translocation of soil constituents resulting in textural differences.

v  The horizon formed by the process of eluviation is termed as eluvial horizon (A2 or E horizon). Translocation depends upon relative mobility of elements and depth of percolation.

Illuviation:

The process of deposition of soil materials (removed from the eluvial horizon) in the lower layer is termed as Illuviation.

o   The horizon formed by this process is termed as illuvial horizon (B-horizon, especially Bt).

o    This is the horizon of gains having the property of stabilizing translocated clay materials.