Accumulation of Materials
Accumulation of materials in the soil formation process refers to the addition and buildup of various substances that contribute to soil development and fertility. These materials accumulate from both organic and inorganic sources, influenced by environmental factors and biological activity. Materials are added to the soil.
Organic Matter Accumulation and Inorganic Matter Accumulation
Leaching and Other Losses
Leaching in soil formation is the process by which water, usually from precipitation or irrigation, percolates through the soil and dissolves soluble substances such as minerals, nutrients, and colloids, carrying them downward from the upper soil layers to lower horizons or out of the soil profile entirely.
Leaching is the removal of soluble components of the soil Column.
Transformation and Illuviation
Transformation
Transformation refers to the chemical and biological alteration of soil materials within the soil profile. This includes processes such as:
- Chemical weathering of minerals, for example, the breakdown of primary minerals like feldspar into secondary minerals like clay.
- Decomposition of organic matter into humus through biological activity.
- Conversion of coarse organic material into decay-resistant organic compounds.
- Changes in mineralogical and chemical composition that modify soil texture, structure, and fertility.
Transformation helps in the maturation of soil by creating stable components like clay minerals and humus, which improve nutrient availability and water retention in the soil.
Illuviation
Illuviation is the process involving the translocation and accumulation of materials leached from upper soil layers into lower horizons. These materials may include:
- Clay particles
- Organic matter (humus)
- Iron and aluminum oxides
- Salts and other minerals
Illuviation typically results in the formation of an illuvial horizon (often the B horizon), characterized by accumulation of these fine materials, which gives distinct color, texture, and density differences compared to upper layers.
Podsolisation
Strongly acidic solutions cause the breakdown of clay minerals. Podzolisation is a specific soil formation process that occurs under cool, humid conditions, typically in acidic environments influenced by coniferous or heath vegetation. It involves the leaching (eluviation) of organic acids and minerals, such as iron (Fe) and aluminium (Al), from the upper soil horizons and their subsequent accumulation (illuviation) in the subsoil.
Laterization
Laterization is a soil formation process characteristic of tropical and subtropical climates with high temperatures and heavy rainfall. It involves the intense chemical weathering and leaching of rock and soil minerals, resulting in the removal of silica, calcium, magnesium, and other soluble elements. This process leaves behind concentrated deposits of iron and aluminium oxides, which give the soil a distinctive reddish-brown colour and a hard, compact texture known as laterite.
Calcification
Calcification is a soil formation process that occurs primarily in warm, semi-arid to arid environments, often under grassland vegetation. It involves the precipitation and accumulation of calcium carbonate (CaCO3) within the soil profile, typically in the B horizon. This happens because calcium dissolved in water moves downward or upward by capillary action, and when conditions such as high temperature and low carbon dioxide concentration prevail, calcium carbonate precipitates out and accumulates.
Gleying
Gleying is a soil formation process that occurs under waterlogged, anaerobic conditions where oxygen availability is severely limited. This process leads to the formation of a gley horizon characterized by bluish-grey, greenish, or grey colors in the soil profile. The lack of oxygen causes iron compounds in the soil to be chemically reduced from ferric (Fe3+) to ferrous (Fe2+) forms. These reduced iron compounds either get removed from the soil or segregate into mottles or concretions, giving the soil its distinctive coloration.
Pedoturbation
Pedoturbation is a soil formation process involving the physical mixing and churning of soil materials. This process leads to the mixing of soil horizons and affects soil structure and composition. Pedoturbation plays a crucial role in soil genesis by destratifying and redistributing organic and mineral matter within the soil profile.
Types of Pedoturbation:
Argillipedoturbation: Mixing caused by the physical swelling and shrinking of clay soils (e.g., Vertisols or black cotton soils), leading to churning and movement of soil materials.
Faunal Pedoturbation: Mixing caused by soil-dwelling animals such as earthworms, ants, rodents, and other burrowing fauna.
Floral Pedoturbation: Mixing caused by plant roots and vegetation activities, including processes like tree tipping that create pits and mounds.
Read More:
Factors Affecting Process of Soil Formation
Podzolization of Soil
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