Soil Microbiology and Formation Quiz

Study Notes

Soil microbiology is the study of microorganisms within soil, their functions, and their activities.
Soil is a key natural resource essential for life on Earth.

A soil profile represents a vertical cross-section of soil layers, known as horizons.
Each horizon has distinct features.
Horizons are labeled: O, A, E, C, B, and R.

O Horizon (Topsoil): Composed of organic matter like leaves, grasses, and decomposed material.
A Horizon (Topsoil): Mineral horizon with accumulated organic matter, rich in nutrients, darker color, high in sand and lower in clay.
B Horizon (Subsoil): Zone of accumulation where substances like iron and aluminum leach from the A horizon. Illuviation occurs here.
C Horizon (Parent Soil): Less affected by soil-forming processes, lacks organic matter and microbial activity.
R Horizon (Rocky Bed): Underlying bedrock, like limestone or sandstone, found beneath the C horizon.

Soil texture and structure influence soil behavior:
- Water holding capacity
- Nutrient retention and supply
- Drainage
- Nutrient leaching
Soil texture is determined by the proportion of sand, silt, and clay particles.

Soil texture influences plant growth characteristics:
- Water-holding capacity
- Permeability
- Soil workability

Sandy Soil: Large particle size, poor water retention, low nutrient value.
Silt Soil: Smaller particles than sand, holds water better than sand, more fertile than other soils.
Clay Soil: Smallest particles, densely packed, retains water well, hinders moisture and air penetration.
Loamy Soil: Mixture of sand, silt, and clay, combines beneficial properties from each, suitable for plant growth.