Role of the factors in the soil formation, soil formation

Role of the factor in the soil formation

The formation of the soil takes too long period. It may take hundreds of years to form. There are various factors that have the key role in the formation of the soil. They are:

a. Parent material

The types of the soil are determined by the presence of the structure, texture and the mineral composition of the rocks. Such parent material does not form the same types of the soil. According to the place and the presence of the rock in varied places, the same rock can also give rise to the various types of the soil. For example, Basalt which is the igneous rock gives the brilliant red, highly weathered soil in the humid tropic environment and the same rock gives the black soil in the semi-arid environment.

b. Climate

The climate is mainly introduced by the rainfall and the temperature including the moisture, humidity, air pressure etc. The amount of the rainfall affects the leaching, profile development and the presence of the CaCO₃ layer. The excess amount of the rainfall in the environment leaches away the Silica, basic materials, that favours for the formation of the hydroxide of the Fe and Al whereas the low rainfall do not leach away the soluble salt as Sa, Mg and Na and hence the soil form alkaline type of the soil, if the sufficient amount of the water is present. On the other hand, the temperature affects the effect of the chemical reaction. the higher is the temperature the faster is the chemical reaction. According to the Stoichiometry, the rate of any chemical is double for each 10^o C rise in the temperature, the temperature speeds of the decay and the loss of the organic matter due to the biological activities.

c. Vegetation Coverage and the Organisms

The varied types of the vegetation in the region also affect the formation of the soil. The root of the plants that grows between or along the crevices joints of the rocks fractures, the rock slowly from where the rainfall and other nutrients reach to the place from outside. Such roots cause the expansive force tending to widen the existing openings and sometimes create the new feature. The insects like the earthworm, snail etc. and the burrowing rodents loosen the soil cover and create suitable for the various external agents to have their own action on the underlying rocks that leads to the weathering.

d. Topography

The topography of the land on the earth is not uniform everywhere. Many steep lands are present. Soils on such land have shallow and poorly developed profiles because the rain water flows rapidly on the steep slopes causing erosionally loses. The soil on the top of the hill is deep but light in the color due to the downward leaching process caused by the rainfall. The soil in the valley is darker, deeper and is found in the more horizons form due to the high amount of the organic nutrient present in the soil.

5. Time

It is one of the important factors as the formation of the soil takes thousands and even the millions of the years.

Soil formation: Soil Profile Development

a. Weathering of the parent material

It includes the development of the parent material. The weathering of the rock is caused by the air, water, moisture and also may take place through the physical, chemical and the biological weathering. The weathering of the rocks causes the breakdown of the rocks into the pieces into its smaller form which proceeds for the further process.

b. Humification

The word humification describes itself as the process which involves the humus or it can be defined as the process which involves the decomposition of the decomposition of the organic matter either it may be plant or animal origin leading to the formation of the humus. It also aids to the formation of the surface humus layer i.e O horizon. The humic substances are present in the surface layer and reach to the lower soil horizon through the percolating water. It may not be present in the arid and sub-arid land and in the tropical and subtropical land as well they may not be accumulated due to the intense microbial activities.

c. Clay Eluviation

The rainfall and the water from different sources cause the downward movement of the soil profile to the lower region which is known as clay Eluviation. This causes the transportation of the soil to the lower region and the upper depleted region is known as E or the Eluvial horizon. The clays in such process are transported through the loss surface or the pores formed by the plant roots or the insects as earthworms or the burrowing animals like rodents and the deposition of the washed soil which have been reached from the eluviation is known as illuviation.

d. Podzolization

The Podzolization is the process of the removal of the oxides of the iron, aluminium, humus, carbohydrates by organic acids and the deposition in the lower horizons. This process mainly involves the leaching process and takes place in the cool and the humid regions with the high rainfall. In the podzolizing processes, the weathering of the acidic parent material like granite, sandstone results in the formation of the acidic soils. The plants which grow on these soils release the organic matter to the soil with the poor in the bases and decomposes to produce the organic matter. Similarly, the organic acid decomposes the aluminium ions then move it to the B horizon.

e. Calcification

The calcification is the process of the precipitation and the accumulation of the calcium carbonate (CaCO₃) in the soil profile. It is mostly formed in the B and the C horizon and take place in the dry soil. In this process, if the amount of the rainfall is low then the basic ions are not dissolved in the and thus leached out forming a soil and the calcium is readily soluble in the carbonic acid form.

Ca + H₂CO₃ → Ca( HCO₃)₂

Ca( HCO₃)₂ temp →CaCO₃ + CO₂ + H₂O

But in the region like arid and the semi-arid region, the leaching is under the restricted condition so the calcium ions are precipitated and deposited as the hard layer of the CaCO_3.

References:

Santra, S. (2004). Environmental Science . India: New Central Book Agency (p) Ltd.

Keller, E.A.Environmental Geology. Columbus, Ohio: Charles E. Miller Publishing Company,Belland Howell Company, 1985.

Mahapatra, G.B.Textbook of Physical Geology. Shahadra,Delhi-110032: CBS Publishers and Distributers Pvt.Ltd., 1992.

Upreti,B.N. and Dhital, M.R.(1996), Landslide Studies and Management in Nepal.