EarthScience Q2L10 - Soil Science

Week 9 - Lesson 2

Overview

  • Focus on soil as a biologically active component of the lithosphere.

  • Exploration of soil formation, types, taxonomies, and impacts of human activities on soil health.

Subsystems of Earth

  • Definition: Interconnected systems that control mass and energy flow on Earth.

Soil Formation

Key Concepts

  • Soil is formed through the weathering of parent rock, influenced by other subsystems.

  • Important Factors:

    • Parent Material: Type of rock influences weathering rate.

    • Time: Longer time enhances soil distinctiveness.

    • Plants and Animals: Organic matter influences weathering.

    • Topography: Land configuration affects water infiltration.

    • Weathering: Major process shaping Earth's surface.

Soil Horizons

Layers of Soil

  • O Horizon: Organic layer at the top, consists of plant material and humus.

  • A Horizon: Topsoil layer enriched with organic nutrients, where most organisms live.

  • E Horizon: Eluviation layer where soil particles wash out, leading to nutrient accumulation in lower layers.

  • B Horizon: Subsoil layer with leached materials from upper layers.

  • C Horizon: Parent material that exhibits little alteration from weathering processes.

Soil Types

Classification Based on Texture

  • Different soil types include:

    • Sandy Soil: Large particles, good drainage.

    • Clay Soil: Small particles, retains water and nutrients.

    • Silt Soil: Intermediate size, retains moisture well.

    • Loam Soil: Balanced mixture of sand, silt, and clay, ideal for plant growth.

USDA Soil Classification Systems

  • Classifies soils based on relative proportions of clay, silt, and sand.

  • Example: 10% silt, 40% clay, 50% sand results in sandy clay.

Soil Taxonomy

Classification of Soils

  • Developed primarily by the USDA-NRCS based on chemical and physical characteristics.

  • Types of Soil:

    1. Gelisols: Frozen soil with permafrost, found in polar regions.

    2. Histosols: Organic-rich wetland soils, dark due to decomposed matter.

    3. Spodosols: Acidic soils with leached materials, typically in sandy regions.

    4. Andisols: Volcanic ash soils with specific leaching characteristics.

    5. Oxisols: Highly weathered tropical soils, poor agricultural capacity.

    6. Vertisols: Soils that shrink and swell, characterized by clay content.

    7. Aridisols: Found in dry areas with minimal organic content.

    8. Ultisols: Weathered tropical/subtropical soils, heavily leached.

    9. Mollisols: Grassland soils rich in nutrients, ideal for agriculture.

    10. Alfisols: Moderately weathered soils, fertile and productive.

    11. Inceptisols: Young soils in humid climates.

    12. Entisols: Extremely young soils with properties of parent material.

Impact of Human Activities on Soil Health

Farming

  • Positive Effects:

    • Use of organic fertilizers enhances microorganism growth.

    • Certain crops stabilize soil structures.

    • Irrigation maintains moisture levels.

  • Negative Effects:

    • Tilling disrupts microbial populations.

    • Pesticides harm soil organisms.

Construction

  • Urbanization decreases soil's capacity to support biodiversity.

  • Rapid degradation and erosion prevalent.

Waste Disposal

  • Pollution from waste degrades soil health.

  • Improper disposal methods further contaminate soils.

Summary

  • Soil is vital for ecosystems and human sustenance.

  • Soil taxonomy categorizes it based on physical and chemical properties.

  • Human practices can adversely affect soil health, making soil conservation crucial for sustainability.