Module 3_ES_Soil Resources-1

Module Overview

  • Topic: Earth Materials & Processes

  • Subtopic 1: Soil Resources

    • Focus: Soil Texture & Soil Triangle

Learning Objectives

  • Understand soil as a complex resource, not merely dirt.

  • Identify the three main components of soil: sediments (sand, silt, clay) and their properties.

  • Grasp the concept of soil texture and its significance for plant growth and water drainage.

  • Learn to classify soil using the soil triangle based on its composition.

Understanding Soil

  • Definition: Soil is a mixture of minerals, organic matter, and water, formed through the weathering of rocks.

  • Importance: Soil is a crucial natural resource, supporting life, providing nutrients, and aiding in food production.

  • Soil Horizons: Distinct layers in the soil, representing different processes and compositions.

Soil Development

  • Stages of Soil Formation:

    1. Soil Begins to Form: Initial weathering processes.

    2. Presence of Simple Organisms: Biodiversity begins to thrive.

    3. Formation of Horizons: Development of distinct soil layers (A, B, C horizons).

    4. Development of Well-Developed Soil: Accumulation of organic matter and mineral particles.

Soil Texture

  • Definition: Refers to the composition of soil based on the size of particles.

  • Particle Sizes:

    • Pebble: 4 – 64 mm

    • Granules: 2 – 4 mm

    • Sand: 2 – 0.0625 mm

    • Silt: 0.0625 – 0.0039 mm

    • Clay: <0.0039 mm

  • Influence on Soil Properties:

    • Effects workings of soil.

    • Impacts water and air retention capabilities.

    • Affects drainage speed.

Testing Soil Texture

Bottle Test

  • Procedure:

    1. Add 5 cm of soil into a bottle and fill with water.

    2. Stir well and let it settle for an hour.

    3. Observe layers forming as particles separate by size.

Soil Triangle Usage

  • After testing, use the Soil Triangle to classify the soil type based on percentage content of sand, silt, and clay.

  • Example classifications:

    • Sandy Loam

    • Silty Clay

    • Clay Loam

  • Interpretation of results through the triangle to determine soil characteristics.

Importance of Soil Texture for Agriculture

  • Proper assessment of soil texture is essential for agricultural planning:

    • Clay-rich soils retain water, ideal for crops like rice.

    • Sandy loams are beneficial for quick-growing crops like cabbage and carrots.

Practice Exercise

  • Apply knowledge of soil texture by using the Soil Texture Triangle with provided exercises to determine soil type.

References

  • Olivar et al (2023) Exploring Life Through Science: Earth Science, 2nd edition. Phoenix Publishing, Inc.

Questions for Review

  • What are the main components of soil and their significance?

  • How can the soil triangle help in determining soil type?