Biogeography

Unit - 05 (Biogeology)

★  Terms related to soil

★  Soil profile

★  Soil genesis

★  Types of soil

Previous Unit - Oceanology 

Biogeography - It is the study of soil and its relationship with vegetation.

Soil - The loose surface material consisting of inorganic and organic matter, various gaseous elements, water and nutrients for vegetation is called soil.

Pedology - The scientific study of soil is known as Pedology. 

True Soil - It is characterised by distinct horizontal layers and the ability to support plant.

Regolith - It is the layer of unconsolidated material derived from the weathering of parent rock (after some time it may become a true soil). It is generally above parent rock.

Pedon - The entire soil column extending down from the surface is called Pedon.

Horizon - It is the distinguishable layer in the soil that has certain distinct chemical and physical properties.

Biosphere - It is that part/sphere of the Earth where all the three other spheres (Lithosphere, Hydrosphere and Atmosphere) are present. It is the life supporting sphere of the Earth.

Soil Profile - The vertical arrangement of different horizons is known as soil profile.

Very high precipitation → Mineral of the top layer got dissolved → seeps to the bottom

Eluviation - It is the downward transport process through which the minerals are removed from the top layer of the soil.

Illuviation - It is the reversal of eluviation where the matter accumulates in the lower horizon through the deposition of minerals.

Soil Genesis - Soil genesis is the process of formation of soil. The process of formation of soil is known as Pedogenesis.

Factors affecting Soil formation (Soil Genesis) 

1. Parent rock
2. Climate
3. Organism
4. Relief features
5. Time period

Note - Trick (Factors → PCORT)

1.   Parent Rock 

• Parent Rock material decides the basic texture, colour and other physical characteristics of the soil (i.e., physical nature of the soil)
• Example - Quartz rocks give rise to Sandy Soil.
• However, the impact of parent rock material diminishes with time.

2.   Climate 

• It is the most important factors which directly affects the nature of the soil by controlling weathering and percolation.
• It leads to the development of different horizons.

3.   Organism (Plant & Animal) 

• Plant roots, burrowing animals, insects and micro-organism help in loosening of soil, air circulation, nutrient cycling, etc.

4.   Relief Features 

• It determines the thickness of the soil and the presence of different layers.
• Example - Mountain → High slope → less thick layers where as in Plains → almost no slope → more thick layers

5.   Time Period 

• Time determines the maturity of the soil.

Soil formation process 

Leaching (means washing) - 

• The percolating water removes humus and soluble bases from the upper horizons and deposits them in the lower horizon (layer). This process is known as leaching.
• It is pronounced in humid areas.
• It is prevalent where Precipitation > Evaporation.

Laterization (excessive leaching)

It is the excessive leaching.

In hot & wet Equatorial rain forest → heavy rainfall → excessive leaching → most of the minerals washed away except Al & Fe → which formed hard crust.

• In hot and wet Equatorial regions, the heavy precipitation and the continuous leaching removes Silica and other major minerals except Iron and Aluminum which accumulates at the surface and leads to the formation of hard Iron crust.

Podzolization 

• In Temperate region, the formation of organic acid (released by micro-organism because of partial decomposition) leads to the removal of Iron, Aluminum and other organic matter leaving a top acidic layer of soil.
• It results in Podzol Soil. 
• It is acidic in nature.

Calcification 

When Evaporation > Precipitation → because of the capillary action water moves upward which also carry dissolved minerals (like Ca) & accumulated at the top layer → which makes the soil fertile → which results in temperate grassland

• It is the process of deposition of Calcium Carbonate near to the top layer of the soil due to the capillary action of the water, in the regions where there is more evaporation than precipitaion.
• It is more active in temperate grassland.

Salinization 

Arid & Semi-Arid areas → Evaporation >>> Precipitation → Sodium gets accumulated to a maximum extent making the soil saltier.

• It is the accumulation of highly soluble Sodium and Magnesium salts in the soil in the regions of high evaporation in Arid and Semi Arid regions.
• Salinization can also be seen in the regions where faulty irrigation methods are practised.
• For example - Soils of Punjab and Haryana are becoming saltier because of Salinization (due to faulty irrigation practice/flood irrigation)

Gleization 

• The colour of the top soil in water logged condition changes due to the reduction reaction. It is known as Gleization.
• It is more prominent in coastal regions.

PYQ 

Salination occurs when the irrigation water accumulated in the soil evaporates, leaving behind salts and minerals. What are the effects of Salination on irrigated land?

1. It greatly increases the crop production.
2. It makes some soil impermeable.
3. It raises the water table.
4. It fills the air spaces in soil with water.

Previous Article - Tides 

Next Article - Types of Soil

Notes on other subjects 

Ancient History

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Art & Culture

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Optional Subject 

Public Administration

Note - This is my Vision IAS Notes (Vision IAS Class Notes) and Ashutosh Pandey Sir's Public Administration Class notes. I've also added some of the information on my own. 

Hope! It will help you to achieve your dream of getting selected in Civil Services Examination 👍