Which one of the following is a major feature of the kandic sub-surface soil horizon?

Correct option is B

Explanation The correct answer is (b) Accumulation of low activity clays. The kandic horizon is a sub-surface soil horizon characterized by the accumulation of low-activity clays, such as kaolinite. These clays have low cation exchange capacity (CEC) due to their mineral composition and weathering processes.
Breakdown of Other Options:
1. (a) Organic matter Fe and Al oxides accumulation:
· This is characteristic of a spodic horizon, not a kandic horizon.
2. (c) Hardpan, strongly cemented by silica:
· This describes a duripan, which is a horizon cemented by silica, not a kandic horizon.
3. (d) Carbonate clays accumulation:
· This is typical of a calcic horizon, which accumulates calcium carbonate, not low-activity clays.
Information Booster 1. Kandic Horizon:
· Found in tropical and subtropical regions with highly weathered soils.
· Dominated by kaolinite and other low-activity clays.
· Formed under conditions of intense weathering and leaching.
2. Low-Activity Clays:
· Clays with low cation exchange capacity (CEC).
· Examples: Kaolinite and halloysite.
3. Other Soil Horizons for Comparison:
· Spodic Horizon: Rich in organic matter and aluminum/iron oxides.
· Duripan: Cemented by silica.
· Calcic Horizon: Accumulates calcium carbonate.
Additional Knowledge · Soil Horizons: Different layers of soil with distinct characteristics.
· Tropical Soils: Often highly weathered, leading to low nutrient retention due to low-activity clays.
· Soil Classification: The kandic horizon is often found in Ultisols and Oxisols.