Geography - Chapter 14 Soils

Mineral matter

Largest component of soil, making up 45% of its composition; derived from broken down bedrock including stones, sand, clay, and silt, which nourish plants.

Humus

Dark, jelly-like substance that constitutes 4% of soil; rich in nutrients formed from decayed plant material, helps bind soil and increases fertility.

Air

Comprises 25% of soil, found in the spaces between soil particles and supplies oxygen and nitrogen to living organisms.

Water

Also makes up 25% of soil, essential for plant growth as it dissolves nutrients and minerals.

Living organisms

Make up 1% of soil; includes earthworms and insects that aerate and mix the soil; bacteria and fungi help in forming humus.

Soil profile

A cross-section view of soil showing different layers, known as horizons.

O horizon

The top layer of soil, containing decomposed leaves and branches that form humus.

A horizon

Known as topsoil, this layer has the highest humus content and the most living organisms.

B horizon

Subsoil that is lighter in color and contains less humus, partially made up of rock material.

C horizon

Consists of rock particles and solid bedrock.

Brown soil

Ireland's most common soil type, dark brown, found in areas once covered by deciduous forests; fertile and well-drained for farming.

Podzol

Grey soil found in coniferous forests in cold, wet upland areas like Wexford, Cork, and Galway; characterized by excessive rainfall and leaching.

Leaching

The process of washing nutrients down through soil horizons, often leading to nutrient loss.

Impermeable layer

A layer in soil through which water cannot pass.