It deprives plants of important nutrients and minerals when it washes them out of reach of their roots.
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It creates a hardpan when iron oxide minerals are washed from topsoil particles. These minerals then collect at the bottom of the A horizon just above the B horizon. This turns into a thin crusty layer that is impermeable to water (does not allow water to flow through it). This causes the A layer to become waterlogged and flooded.
Can you identify the A horizon, the hardpan and the B horizon in this image?
2 The Breakdown of Plant Litter
Plant litter – dead leaves and twigs that have fallen on top of the A horizon – are broken down by insects, such as earthworms and beetles, and micro-organisms into humus, the black, jelly-like substance that contributes to soil fertility.
Oxygen is also needed to assist in the breakdown of plant litter into humus, because its presence in the soil helps keep organisms alive.
The process of plant litter changing into humus is called humification.
1. What is leaching? Explain how it affects soil formation.
