Soil is a natural resource formed by wheathering (breakdown) of rocks. It has been defined as they matrix (sand slit clay) containing living biomass and dead organic matter with some concentration of air and water.
It is a rich source of organic and inorganic material that support plant life and microscopic communities. Inorganic material include elements derived from weathering and Fragmentation of parent rock material.
organic components include organic wastes, dead remians of plant and animals and their decomposition products.
Formation of soil
The formation of soil formation begins with the changes in the parent material (rocks)
Accumulation of raw material followed by build up of organic material at the surface..
Various physical ‚chemical, biological and anthropogenic process are invlovwd in the alteration of the parent material to form soil.
Two main steps invoved in soil formation include:
- Weathering of rocks :
- The breakdown of rocks is called weathering.it cna be physical and chemical. Physical weathering occurs by mechanical forces. Changes in temperature cause contraction or expansion of rocks leading to formation of cracks and fissures in rocks.
- This breaks rocks into samller pieces. Low temperature freezes the water present in the rock crevices causing expansion and this force breaks into small pieces besides these, hail, rainfall, wind also help in breaking of rocks into smaller particles due to fraction.
Chemical weathering :
It is brought about by action of water or activities of organisms present in soil. Water brings chemical changes in rocks due to dissolution. Oxidation reduction and organic acids produced by microbes assist in the breakdown of rocks and add organic matter to soil.
2. Mineralization and Humification:
The small pieces of rocks or particles prodced by weathering of rocks get converted into a homogenous matrix via the process of minerlization. Plants and animals play an important role in this process
The roots of the plants invade the soil particles further breaking the particle into fine materials. The microbes associated with the roots of plants secrete organic acids and humic acids that further assist in breakdown of rock material to fine soil particles.
Microorganisms such as bacteria, fungi and actinomycetes assists in the decompistion process.
In the process, organic compounds get converted into inorganic nutrients. The breakdown of organic compounds leads to formation of simple products such as carbon dioxide, water and Minerals.this process is called Minerlization forms the humus which is dark, homogenous, amorphous, collodial substances.
Humus gives lose texture to the soil which provides aeration and helps in reatining water and nutrients.
Factors affecting soil formation include :
- Parent material
- Cimate
- Topography ( elevation)
- Biological factors
- Time
SOIL : Types of Soil, Classification of Soil, Soil Biota and Fertility : Click Here