Soil formation, or pedogenesis, is influenced by a combination of factors that interact over time to shape the characteristics of a particular soil.

 

Factors of Soil Formation - 

Soil formation, or pedogenesis, is influenced by a combination of factors that interact over time to shape the characteristics of a particular soil. These factors are often referred to as the "factors of soil formation"

Some scientist gave their own concept which are given below 👇

 

 

 

Active factors- 

 

1. Climate - 

rainfall and temperature are most active agent. 

Directly affects by supplying water and heat to react with parent material.

 Indirectly flora and fauna furnishes to form organic matter energy. 

Energy acts on rocks and minerals as acid and salts released during decomposition. 

 

Endodynamomorphic soil under influence of parent material

Ectodynamomorphic soil under influence of climate

 

Rainfall:

Rain fall > PET (Potential evapo-transpiration ) leaching of bases take place. 

pH ↓. 

Soils become acidic. Vegetation will be more. 

The soils have more organic matter due to less decomposition. 

Soils exhibits good horizonation.

High rain fall runoff (↑) and erosion(↑) in sloppy areas

Accumulation of materials in plains leading to the development of different soils.

 

Arid and semi arid regions: 

Rainfall < PET. 

Here percolation of water will be less. 

So bases accumulate. 

pH (↑). 

Soil horizonation is poor.

 

Temperature:

According to Vant Hoff’s law For every 10ºC (↑) in temperature , the chemical reactions (↑) by a factor of 2 or 3 times. 

Temperature (↑), weathering of rocks (↑) due to more biological activity and faster chemical reactions. 

Weathering in tropical climate > temperate climate.

In cold humid climate the soils are grayish and in warm humid climate the soils are red in colour.

 2. Organism (Biosphere)- 

It contains both flora and fauna

Flora - Micro organism, Plants, grasses, forests etc.

Fauna - Earthworm, rodents, ants termite etc.

 

Organic matter (↑), microbial activity (↑) available nutrients (↑).

Soil organisms play a major role in profile differentiation.

O.M. accumulation, profile mixing, nutrient cycling and structural stability enhanced by M.O.. 

Vegetative cover (↑), natural soil erosion rates (↓),  mineral surface removal (↓).

Human activity like deforestation, tilling soils, irrigation and fertilization significantly influences soil forming processes.

 3. Vegetation - 

Initially vegetation of an area influenced by parent material but in later stage vegetation govern by climate.

Types of soil is depend on vegetation of an region.

 

Organic content in grass land > forested land

Aggregation in soil is > grass land area.

 

Coniferous vegetation soil acidity (↑)  because the leaves of cone trees (↓) basic cations i.e. Ca, Mg,K,Na

Leaching (↑)

Passive factors- 

 1. Parent material - 

Influence soil character like texture (can’t altered). 

Basalt - red soil, black cotton soil

Acid igneous rock - light textured podzolic soil.

Basic igneous rock - fine textured cracking clay soil.

Basic alluvium (when transportation and deposition of parent material takes place by water) material - fined coarse textured soil

 

Element found in rock play role in following condition - 

Si and Al - skeleton for production of secondary mineral

Fe and Mn - red colour to soil and oxidation and reduction 

Na and K - dispersing for clay and humus coloids

Ca and Mg - flocculation effect for soil stability

 

 2. Relief or topography - 

Soil profile - Thick in plain and thin in slopy area due to(↑)erosion on slop.

Soil climate - >humid in gentle slopes than steepy slope

Moist or wet in valley or depressed land.

Soil on steepy slope are shallow, stony less weakly developed soil with less horizonization due to (↑)erosion.

 

Red soils  →   Higher topography

Black cotton soil  → Lower topography

 

 3. Time - 

(↑) time duration required for development of distinct layer of soils = genetic horizons = matured soil with A,B,C horizons.

Horizons develops more rapidly in warm humid and forested area than in cool or hot and arid condition.

 

Soils on river flood plane = younger due to periodic erosion.

 

 

 

UPSC Agriculture Optional Previous Year Question Differentiate between active and passive factors of soil formation. 2010