Soil Composition, Formation, Horizons, and Scientific Study

All flashcards

What are the four major components of soil?

Inorganic mineral matter, organic matter, water, and air. Their proportions vary with conditions such as vegetation, compaction, and water availability.

How do organic soils differ from mineral soils?

Organic soils form through sedimentation and are composed mainly of organic matter. Mineral soils form through rock weathering and consist mainly of inorganic material.

What does humus do in soil?

Humus improves soil structure, helps retain moisture, supplies plants with water and minerals, returns nutrients, and supports soil microorganisms.

What are the soil particle size ranges for sand, silt, and clay?

Sand is 0.1–2 mm in diameter, silt is 0.002–0.1 mm, and clay is smaller than 0.002 mm.

What five factors influence soil formation?

Parent material, climate, topography, biological factors, and time.

Quiz questions

1. What is a soil profile?Answer: A vertical section through the soil layers.
2. What commonly happens in the B horizon?Answer: Fine material that moved downward accumulates there.
3. How can geographic information systems help soil scientists?Answer: They help analyze relationships among landforms, vegetation, and climate.
4. Which horizon pattern may be found in mature soils?Answer: All four main horizons may be present, sometimes with additional layers.
5. In ideal soil, approximately what proportion of its volume is pore space?Answer: About one-half.