[Campbell Biology P.856] Based on the "Organic Components" section, which of the following a... | Practice Question

Based on the "Organic Components" section, which of the following are beneficial functions of humus in topsoil? Select all that apply

  • A: Increases the soil's capacity to exchange cations.
  • B: Decreases water retention, allowing for faster drainage.
  • C: Prevents clay particles from packing together, maintaining a crumbly soil structure.
  • D: Serves as a reservoir of mineral nutrients released gradually by microorganisms.
  • E: Directly binds to H+ ions, increasing soil pH.

Explanation

The 'Organic Components' section states that humus 'increases the soil's capacity to exchange cations' A , 'prevents clay particles from packing together and forms a crumbly soil that retains water but is still porous enough to aerate roots' C , and 'is a reservoir of mineral nutrients that return gradually to the soil as microorganisms decompose the organic matter' D . Humus retains water, it does not decrease water retention B . While humus plays a role in cation exchange, its primary stated function isn't directly increasing soil pH by binding H+ ions E ; earthworms are mentioned for lowering pH.