diagnostic horizon

pedology

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June 11, 2026

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In pedology, a diagnostic horizon is a key concept used for classifying soils. These horizons are defined by the specific types of accumulated weathering products they contain, such as clay, mixtures of iron oxides and humus, or soluble salts. They can also be characterized by the presence of a hard, impermeable layer, like an indurated calcium carbonate or iron-rich layer.1

Soil horizons are distinct layers within the soil profile, formed by the actions of organisms and percolating water. From the surface downward, common horizons include O (organic matter), A (humus accumulation), E (leached, bleached appearance), B (accumulation of material from upper layers), C (unweathered parent material), and R (bedrock). Diagnostic horizons are crucial for understanding soil properties and classification.12

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horizon
…concept is that of subsurface diagnostic horizons. These are characterized by the type of accumulated weathering products that they contain (e.g., clay, mixtures of iron oxides and humus, or soluble salts) or by the possible presence of a hard, impermeable layer (e.g., an indurated calcium carbonate or iron-rich layer).
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…concept is that of subsurface diagnostic horizons. These are characterized by the type of accumulated weathering products that they contain (e.g., clay, mixtures of iron oxides and humus, or soluble salts) or by the possible presence of a hard, impermeable layer (e.g., an indurated calcium carbonate or iron-rich layer).
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soil
Soil classification
…systems is the notion of diagnostic horizons, well-defined soil layers whose structure and origin may be correlated to soil-forming processes and can be used to distinguish among soil units at the highest level of classification (see the table of primary diagnostic horizons). Diagnostic horizons may be found very near the…
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…systems is the notion of diagnostic horizons, well-defined soil layers whose structure and origin may be correlated to soil-forming processes and can be used to distinguish among soil units at the highest level of classification (see the table of primary diagnostic horizons). Diagnostic horizons may be found very near the…
Read More