The horizon of a soil profile which encourages the greatest level of microbial activity is

  • A A - horizon
  • B B - horizon
  • C C - horizon
  • D D - horizon

The correct answer is A. A - horizon

The A-horizon is a weathered layer that contains an accumulation of humus (decomposed, dark-coloured, carbon-rich matter) and microbial biomass that is mixed with small-grained minerals to form aggregate structures.

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