a-horizon

noun

Meaning

The uppermost layer of soil, characterized by high organic matter content and intense biological activity.

Examples

  • The A-horizon is often darker than the layers beneath it due to the accumulation of decomposed plant material.
  • Farmers prioritize protecting the A-horizon because it contains the majority of the nutrients required for crop growth.

Synonyms: topsoil, surface soil, humus layer, eluvial horizon