Notes
Soil is a mixture of weathered rock, organic matter (humus), water and air.
- Soil forms slowly: centuries to make a few centimeters.
- A soil profile has horizons: A (topsoil, rich in humus), B (subsoil), C (partly weathered rock), then bedrock.
- Climate, parent rock, organisms, slope and time all affect soil.
- Topsoil is vital for farming; erosion and poor farming practices can remove it.
Practice
Which soil horizon is richest in organic matter?
Humus accumulates near the surface.
Which is NOT a factor in soil formation?
Moon phase does not control soil formation.
Soil forms:
That is why topsoil loss is a serious problem.
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