(a) Explain any four processes of soil formation (b) In what four ways is soil important?

(a) Four processes of soil formation

• Weathering of parent rock: The breaking down of the underlying rock by physical, chemical and biological weathering produces the mineral particles that form the basis of the soil.
• Addition of organic matter (humification): Dead plants and animals decay and are broken down by micro-organisms to form humus, which is added to the mineral matter and enriches the soil.
• Leaching and eluviation: Rainwater passing down through the soil dissolves and washes soluble minerals and fine material from the upper layers down to the lower layers, helping to develop distinct soil horizons.
• Action of living organisms and climate: Burrowing animals (earthworms, termites), plant roots, and the effects of temperature and rainfall mix the soil, aerate it and speed up the chemical changes that continue soil development over a long time.

(b) Four ways soil is important

• It is the medium for plant growth, supplying anchorage, water and nutrients, and so is the basis of agriculture and food production.
• It provides pasture and grazing land for the rearing of animals.
• It supplies raw materials such as clay for pottery, bricks and building, and holds ground water.
• It supports forests and natural vegetation that provide timber and other products, and it is home to countless organisms that keep the ecosystem going.