The Kandic horizon is a subsurface horizon in soil taxonomy characterized by its thickness, clay content, and depth interval. It is a diagnostic horizon used to classify soils based on their properties and formation processes.
Key Facts
- Definition: The Kandic horizon is a subsurface horizon in soil taxonomy that is characterized by its thickness, clay content, and depth interval.
- Thickness: The Kandic horizon typically has a minimum thickness of 15-30 cm, depending on the depth of the soil.
- Clay content: The Kandic horizon is identified by an increase in clay content from an overlying eluvial horizon. The amount of clay increase ranges from 4% to at least 8% for different clay contents in the eluvial horizon.
- Depth interval: The clay increase in the Kandic horizon occurs within a depth interval of 50-200 cm from the overlying eluvial horizon.
- Cation Exchange Capacity (CEC): The Kandic horizon has an apparent CEC of ≤16 cmol(+)/kg clay and an apparent effective CEC of ≤12 cmol(+)/kg clay.
- Clay illuviation: Unlike other diagnostic subsurface horizons, the Kandic horizon does not require evidence of clay illuviation.
Thickness
The Kandic horizon typically has a minimum thickness of 15-30 cm, depending on the depth of the soil. This thickness requirement helps distinguish the Kandic horizon from other diagnostic horizons with clay enrichment.
Clay Content
The Kandic horizon is identified by an increase in clay content from an overlying eluvial horizon. The amount of clay increase ranges from 4% to at least 8% for different clay contents in the eluvial horizon. This clay increase indicates the accumulation of clay minerals in the Kandic horizon, which is a key characteristic for its identification.
Depth Interval
The clay increase in the Kandic horizon occurs within a depth interval of 50-200 cm from the overlying eluvial horizon. This depth interval helps define the location of the Kandic horizon in the soil profile and distinguishes it from other horizons with clay enrichment.
Cation Exchange Capacity (CEC)
The Kandic horizon has an apparent CEC of ≤16 cmol(+)/kg clay and an apparent effective CEC of ≤12 cmol(+)/kg clay. These CEC values indicate the low activity of the clay minerals in the Kandic horizon, which is a characteristic feature of these soils.
Clay Illuviation
Unlike other diagnostic subsurface horizons, the Kandic horizon does not require evidence of clay illuviation. This means that the clay accumulation in the Kandic horizon is not necessarily the result of clay movement from an overlying horizon. Instead, it may be due to in-situ weathering and clay formation within the Kandic horizon itself.
Conclusion
The Kandic horizon is a diagnostic subsurface horizon in soil taxonomy that is defined by its thickness, clay content, depth interval, CEC, and lack of evidence for clay illuviation. These characteristics help distinguish the Kandic horizon from other horizons with clay enrichment and provide valuable information for understanding soil formation processes and classifying soils.
FAQs
What is a Kandic horizon?
The Kandic horizon is a subsurface horizon in soil taxonomy characterized by its thickness, clay content, depth interval, CEC, and lack of evidence for clay illuviation.
How thick is a Kandic horizon?
The Kandic horizon typically has a minimum thickness of 15-30 cm, depending on the depth of the soil.
How is the clay content of a Kandic horizon determined?
The Kandic horizon is identified by an increase in clay content from an overlying eluvial horizon. The amount of clay increase ranges from 4% to at least 8% for different clay contents in the eluvial horizon.
What is the depth interval of a Kandic horizon?
The clay increase in the Kandic horizon occurs within a depth interval of 50-200 cm from the overlying eluvial horizon.
What are the CEC characteristics of a Kandic horizon?
The Kandic horizon has an apparent CEC of ≤16 cmol(+)/kg clay and an apparent effective CEC of ≤12 cmol(+)/kg clay.
How does a Kandic horizon differ from other diagnostic subsurface horizons?
Unlike other diagnostic subsurface horizons, the Kandic horizon does not require evidence of clay illuviation. This means that the clay accumulation in the Kandic horizon is not necessarily the result of clay movement from an overlying horizon.
What are some of the key characteristics used to identify a Kandic horizon?
The key characteristics used to identify a Kandic horizon include its thickness, clay content, depth interval, CEC, and lack of evidence for clay illuviation.
What is the significance of the Kandic horizon in soil classification?
The Kandic horizon is a diagnostic horizon used in soil taxonomy to classify soils based on their properties and formation processes. It provides valuable information for understanding soil formation processes and helps distinguish soils with different characteristics.