Soil Formation and Soil Profile

🧾 Soil Formation and Soil Profile

🌱 Factors Affecting Soil Formation

1. Parent Rock:
   Determines the texture, mineral content, colour, and chemical properties of the soil.

   • Example:

     • Black Soil – from igneous rocks (residual)

     • Alluvial Soil – from sedimentary rocks (transported)

2. Relief (Topography):

   • Steep slopes → rapid erosion, thin soil

   • Gentle slopes → better water retention, more fertile, balanced erosion

3. Climatic Conditions:

   • Rainfall and temperature affect weathering of rocks and humus formation

4. Living Organisms:

   • Plants and animals contribute organic matter (humus)

   • Roots break rocks, microorganisms like fungi and bacteria decompose minerals

5. Time:

   • Older soils have thicker profiles and are more fertile

   • Mature soil develops over thousands of years

🧱 Soil Profile

A soil profile is the vertical section of different soil layers from the surface down to the bedrock.

1. Horizon A (Topsoil)

   • Rich in organic matter (humus)

   • Dark, porous, supports plant roots

   • Leaching is common here

2. Horizon B (Subsoil)

   • Contains inorganic materials like clay, silt, sand

   • Less humus, more minerals

   • Together with A forms true soil

3. Horizon C (Rock Fragments)

   • Made of partially weathered rock pieces

   • Source of material for true soil

4. Horizon D (Parent Rock)

   • Also called bedrock

   • Unweathered solid rock at the bottom

🧪 Fun Fact: Europe alone has more than 10,000 types of soil identified by scientists!