SOIL HORIZONS/PROFILE

Soil = A thin layer of natural material formed by weathering and erosion, crucial for life

Climate = Most important factor in soil composition

How long does soil take to form? = 400 years for 1cm

4 layers of soil = Organic Layer (O) Topsoil (A) Subsoil (B) Parent Rock (C)

O (Organic Layer) = Surface, made up of plant litter and decomposition

A (Topsoil) = First layer of soil, organic matter, humus, dark, leaching

B (Subsoil) = Lighter in colour, zone of accumulation - minerals and rainwater build up here, these minerals create a layer of impermeable material called hardpan (waterlogging)

Waterlogging = When too much water fills the soil, causing inability for air to reach plant roots

Impermeable = DOES NOT allow liquid to pass through

C (Parent Rock) = Made up of partially weathered parent material, bedrock, undisturbed by weathering process

Leaching = Minerals, humus and nutrients are washed down through the soil horizons by rainfall

Impact of Leaching = As the nutrients are leached down, they become out of reach for plant roots causing death - also causes waterlogging