Soil organic matter are remains of dead living things that is dead animals and plants. Decaying of dead living things which leads to formation of soil organic matter, is affected by number of factors as we will explain below.
The soil formation process depends upon the presence of new soil material which is either acquired by denudation or deposition. Denudation is the abrasion of present rock material by the action of ice, water or wind. Deposition is the accumulation of new materials that have been eroded from another place such as river gravels or blown gravel or the creation of new rocks due to volcanic action or the uplift of the ocean.
So, these two actions are responsible for availing new parent materials that begin the process of soil formation. Examples of new parent materials include rocks, loess, gravel, alluvium, scree, and sand. Soils then begin to form from these materials through the process of weathering together with other chemical and physical processes as outlined below.
Process of Soil Formation Accumulation of materials Materials are added to the soil such as organic matter and decomposing materials or new mineral materials deposited by the forces of ice, water or wind and they accumulate over time.
This happens in the top layer of the soil. In poorly drained soils, the organic materials accumulate since water-logging prevents it from being oxidized or broken down by soil organisms. In well drained soils, the materials accumulate when they are held up by the root systems.
Depositions by the forces of wind, water or ice equally contribute to the accumulation of new materials. Some plants with the help of bacteria fix atmospheric nitrogen and ammonia compounds into the soil as nitrates.
Leaching and losses Through the movement of water, wind, ice or the uptake of the accumulated materials by plants, the new particles including clay, organic matter, clay, silt or other chemical compounds are leached and eroded away or taken up from the soil by plants.
As a result, the physical and chemical compositions of the new accumulated materials together with the soil parent material are altered. A prime example is the leaching out of some carbonates, magnesium and other minerals.
Transformation and illluviation Here the soil particles held in the suspension after the leaching such as clay are transformed after which they accumulate. Transformation is the chemical weathering of silt, sand, and the formation of clay minerals as well as the change of organic materials into decay resistant organic matter.
After, the clay and other accumulated materials are washed from the upper horizons and deposited in the lower horizons. The plants and animals are also responsible for transformation of the soil by physically and chemically breaking down the materials.
The soil begins to take shape on its own through transformation, which improves natural drainage and nutrient composition.
Podsolisation and translocations Podsolisation takes place when strong acidic solutions breakdown the clay minerals. Accordingly, aluminum, silica and iron form complex materials together with organic compounds in the soil. After a relatively extended time, the movements of the accumulated mineral precipitate such as iron oxides minerals are responsible for the reddish and brownish color of the different soil horizons.
The same applies to the alterations in structure, texture, and other mineral compositions. The soil horizons are then cemented by the carbonate, iron, and silica minerals.Video: The Formation and Composition of Soil: Definition and Factors In this video lesson you will learn how soil is formed and what it is made of.
You will also learn about how soil is classified and distributed in layers underground. Plants, animals, micro-organisms, and humans all affect soil formation. Certain bacteria (cyanobacteria that can fix their own nitrogen) and lichens (semi algae, semi fungi) have a key role in building up early ‘layers’ of organic matter and generating soil formation in the first place.
A. Moisture as a Soil-forming Factor: 1. Discussion of Moisture Criteria; 2. Relationships between Soil Properties and Moisture Factors: a.
Organic Constituents of the Soil; b. Inorganic Constituents of the Soil. B. Temperature as a Soil-forming Factor: 1. Discussion of Temperature Criteria; 2.
Relationships between Soil Properties and Temperature.
C. A. Moisture as a Soil-forming Factor: 1. Discussion of Moisture Criteria; 2. Relationships between Soil Properties and Moisture Factors: a. Organic Constituents of the Soil; b. Inorganic Constituents of the Soil.
B. Temperature as a Soil-forming Factor: 1. Discussion of Temperature Criteria; 2. Relationships between Soil Properties and Temperature. C. The physical factors affecting the gully formation refer to those factors, which affect the rate and amount of surface runoff, which directly in turn to cause the gully formation.
The precipitation, land topography, soil properties and vegetative cover are mainly considered as . Soil organic matter are remains of dead living things that is dead animals and plants. Decaying of dead living things which leads to formation of soil organic matter, is affected by number of factors .