Understanding Soil: Formation and Erosion

Oct 9, 2024

Lecture Notes: Soil Formation and Erosion

Introduction to Soil

  • Importance of Soil: Foundation for plant growth, water filtration, and various functions.
  • Objective: Describe soil characteristics and formation.

What is Soil?

  • Composition: Mix of geological and organic components.
    • Geological Components: Sand, silt, and clay.
    • Organic Components: Includes humus, nutrients, water, air, and living organisms.
  • Humus: Decomposed organic matter, providing nutrients and structure.
  • Nutrients: Ammonium, phosphates, nitrates critical for plant growth.
  • Living Organisms: Earthworms, fungi, bacteria, aiding in nutrient recycling.

Roles of Soil in Ecosystems

  1. Supports Plant Growth:
    • Anchors plant roots.
    • Provides water and essential nutrients (N, P, K, Mg).
  2. Water Filtration:
    • Soil traps pollutants, clean water helps recharge groundwater.
  3. Nutrient Recycling:
    • Decomposers break down organic matter, return nutrients.
  4. Habitat:
    • Supports earthworms, fungi, bacteria, and other organisms.

Weathering and Erosion

  • Weathering: Breakdown of rocks into smaller pieces.
    • Types: Physical (wind, rain), chemical (acids), biological (plant roots).
  • Erosion: Transport of weathered rock particles.
    • Process: Detachment, movement, deposition.

Soil Formation

  • From Below: Weathering of parent material/bedrock contributes minerals.
  • From Above: Decomposition of organic matter adds humus.
  • Factors Affecting Formation:
    1. Parent Material: Influences soil pH and nutrient content.
    2. Topography: Steep slopes may hinder formation due to erosion.
    3. Climate: Temperature and precipitation influence organic matter breakdown.
    4. Soil Organisms: Decomposers increase rate of soil formation.

Soil Horizons

  1. O Horizon: Organic layer with plant material, traps moisture.
  2. A Horizon (Topsoil): High in humus and minerals, most biological activity.
  3. B Horizon (Subsoil): Contains clay, fewer nutrients, less organic matter.
  4. C Horizon: Least weathered, resembles parent material.

Soil Degradation

  • Loss of Topsoil: Due to tilling and vegetation loss, reduces productivity.
  • Compaction: Machines/livestock compress soil, reducing pore space for water.
  • Nutrient Depletion: Continuous cropping reduces soil fertility.