Soil Profiles (DP IB Environmental Systems & Societies (ESS))

Soil Profiles

• Soil profiles provide a visual representation of the different layers or horizons present in a soil system

  • These horizons reflect the processes and materials that have shaped the soil over time

  • There are six main horizons

A soil profile is a visual representation of the different horizons present in a soil system

O horizon

• The O horizon, also known as the organic horizon, is the uppermost layer

  • It is composed mainly of organic matter such as leaf litter, decaying plant material, and organic debris

  • It is rich in nutrients and serves as a site for nutrient cycling and organic material decomposition

A horizon

• The A horizon, also called the topsoil, is a mixed mineral and organic horizon

  • It is usually darker in colour due to the accumulation of organic matter

  • This layer is important for plant growth as it contains nutrients and provides a favourable environment for root development

E horizon

• The E horizon, also known as the eluvial or leached horizon, is characterised by the leaching or removal of minerals and nutrients due to downward movement of water

  • It often appears lighter in colour than the surrounding horizons

B horizon

• The B horizon, also called the illuvial or deposited horizon, is the layer where minerals and nutrients leached from the upper horizons accumulate

  • It often exhibits different colours, textures, or chemical properties compared to the horizons above and below it

C horizon

• The C horizon represents the weathered parent material from which the soil has formed

  • It is typically composed of partially weathered rock fragments and may contain limited organic matter

  • The properties of the C horizon influence the development and characteristics of the upper horizons

R horizon

• The R horizon, also known as bedrock, is the underlying solid rock that forms the base of the soil profile

  • It is often unweathered

  • It is relatively unaffected by biological activity and represents the original geological material from which the soil formed

• These layered horizons in a soil profile provide information about the soil's composition, nutrient content, water-holding capacity, and drainage characteristics

• They help scientists, farmers, and land managers understand the properties and fertility of soils, enabling them to make informed decisions regarding land use, crop selection, and soil conservation practices