Is Subsoil Mostly Made of Solar Energy or Petroleum or Small Rocks or Solid Rocks?
- The uppermost layer of the soil is the humus or litter of decaying organic matter; this is called the O horizon. Beneath it lies the A horizon or topsoil, then the E horizon, the B horizon or subsoil, and finally the C horizon and parent rock. Nutrients are leached out of the E horizon and accumulate in the subsoil below it over time.
- The subsoil or B horizon consists chiefly of rock that has been broken down into small rock particles over time. It also includes a fairly substantial amount of nutrients, however, largely because nutrients leach out of the overlying E horizon into the subsoil. Although the subsoil contains many nutrients it is still more nutrient-poor than the topsoil.
- Since the subsoil is composed primarily of small rock particles, solid rocks only play a contributing role as they break down to furnish the subsoil with more material. Solar energy is important as well; plant life needs sunlight to grow, and when plants die the nutrients they contain are recycled back into the soil and subsoil as they decay.
Petroleum is not part of subsoil, but can sometimes contribute to its composition by means of human activity. Humans may use energy from petroleum to make fertilizers which are added to the soil to increase its nutrient concentration.