A Cambisol is a reference soil group (RSG) in the World Reference Base for Soil Resources (WRB) soil classification system. It represents a large group of weakly to moderately developed soils that show evidence of initial soil formation but lack the diagnostic horizons characteristic of more highly developed soil types. The term "Cambisol" is derived from the Latin word cambiare, meaning "to change," reflecting the presence of visible alterations within the soil profile.
Characteristics
Cambisols are primarily characterized by the presence of a cambic horizon. This horizon is defined by:- Color or Structure Changes: Evidence of pedogenic alteration (soil-forming processes), often seen as a change in color, structure (e.g., blocky or prismatic peds), or accumulation of carbonates or gypsum relative to the parent material.
- Absence of Strong Illuviation: Unlike more developed soils, the cambic horizon does not show significant evidence of clay illuviation (movement and accumulation of clay particles), iron oxides, or organic matter that would form argic, spodic, or other diagnostic horizons.
- Depth: It must be at least 15 cm thick.
- Texture: Typically has a sandy loam to clay texture.
Other general characteristics include:
- Parent Material: Cambisols can develop from a wide range of parent materials, including unconsolidated sediments (alluvium, loess, till) and weathered bedrock.
- Drainage: They typically have good to moderate internal drainage.
- Fertility: Natural fertility can vary from low to high depending on the parent material and the degree of weathering.
- Organic Matter: Surface horizons often contain moderate amounts of organic matter.
Formation and Occurrence
Cambisols represent an intermediate stage in soil development. They form under various climatic conditions, from humid tropics to temperate and boreal zones, wherever there has been sufficient time for initial pedogenic processes to occur but not enough for the formation of more advanced diagnostic horizons.Common environments for Cambisol formation include:
- Young Geomorphic Surfaces: Such as recent alluvial plains, glacial moraines, and volcanic ash deposits.
- Stable Slopes: In mountainous or hilly regions where erosion prevents the accumulation of highly developed horizons or on stable, older landforms where specific conditions prevent further development.
- Various Climates: While common in temperate and boreal regions, they are also found in the humid tropics on parent materials that are not highly weathered.
Globally, Cambisols are one of the most widespread soil groups, covering significant areas of Europe, Asia, and North America, as well as parts of South America and Africa.
Sub-types and Qualifiers
The WRB system uses various qualifiers to specify the properties of Cambisols. Some common examples include:- Eutric Cambisols: Rich in bases, indicating good natural fertility.
- Dystric Cambisols: Low in bases, often acidic and less fertile.
- Calcaric Cambisols: Containing significant amounts of calcium carbonate.
- Gleyic Cambisols: Showing signs of temporary or permanent waterlogging.
- Vertic Cambisols: With properties related to shrink-swell clays.
These qualifiers provide more detailed information about the soil's chemical and physical characteristics, allowing for more precise management decisions.
Agricultural Significance
Due to their moderate stage of development, good drainage, and often favorable texture, Cambisols are generally productive soils. They are widely used for:- Arable Farming: Suitable for a broad range of crops, including cereals, root crops, and vegetables.
- Forestry: Support diverse forest ecosystems.
- Pasture: Used for grazing livestock.
Their moderate fertility means that some Cambisols may benefit from fertilization to optimize yields, especially the Dystric varieties. Soil conservation practices are important to prevent erosion and maintain organic matter levels.
See also
- World Reference Base for Soil Resources (WRB)
- Soil classification
- Pedogenesis
- Luvisol
- Regosol