Soil profile
Also called: Soil horizons · Topic: Soils of India: Types, Degradation and Conservation · NCERT: Class 10, Ch 1 "Resources and Development"; Class 11, Ch 1 "Geography as a Discipline"; Class 11, Ch 5 "Geomorphic Processes"
Meaning
A soil profile is a vertical cut through the soil, from the surface down to the solid rock below. Each layer in it is called a horizon. From top to bottom the horizons are: O (fallen leaves), A (topsoil, rich in humus, the dark, nutrient-rich matter from rotting plants and animals), B (subsoil, where clay, iron and lime washed down from above build up), C (broken-down parent rock) and R (solid bedrock). Mature soils have clear horizons. Young soils do not, because they have not had enough time to form layers.
Example
On the old red soils of the Deccan Plateau, a pit or road cutting shows clear layers, with darker topsoil above reddish subsoil. In the fresh river alluvium of the Ganga floodplain, the layers are hard to see.
Don't confuse with
- Soil texture: texture is the size of the soil particles (sand, silt, clay). The profile is the order of layers from top to bottom.
- Eluviation and illuviation: these are processes inside the profile. In eluviation, water washes material out of the A horizon. In illuviation, that material collects in the B horizon.