Soil and change

•Explain the causes of soil degradation.•Discuss the environmental and socio-economic consequences of this process, together with management strategies. (4hours)

Patterns in environmental quality and sustainability

4 hours

Lesson 1

Lesson 1

What is soil and soil degradation?

What is soil?

• Soil is the uppermost layer of the earth.• Frequently less than 1m deep

• Soil is essential to all life on earth – it provides the means of growing food and grazing animals.

• It takes thousands of years to form• It is made up of a mixture of:

– Mineral matter (weathered rocks)– Organic matter (e.g. rotted leaves)– Air– Water

Soil composition

Back to back mapping

...the soil system

The Soil System

The soil profile• A fully developed

soil displays a sequence of layers.

• These are shown in a soil profile.

• Layers are called HORIZONS

• Soil profiles can be seen by digging a soil pit in the field

• O horizon – the organic layer made up of leaf litter at various stages of decomposition. Contains lots of nutrients and is therefore an important constituent of soil.

• A horizon – this is the topsoil. It is a mixture of weathered rock material from below and organic matter from above. e.g. earthworms. This is usually the most fertile soil horizon.

• B horizon – this is the subsoil. It contains a higher proportion of weathered rock material. generally less fertile because it is further from the source of organic matter.

• C horizon – this is weathered rock material which provides the soil with its mineral matter.

Soil Structure• Describes the way individual

particles of soil group together to form lumps called peds.

• Soils with a crumb structure are favoured for agriculture because they are well drained.

The temperate and prairie soils are better for agricultural use. Explain why.

What is going on in these photographs?

Soil degradation

• Soil degradation is the temporary or permanent decline in the productive capacity of the soil in a given area.

• Soil degradation is, in itself, an indicator of land degradation, which describes how one or more of the land resources (soil, water, vegetation, rocks, air, climate, relief) has changed for the worse.

Human causes of soil degradation

What is the issue?

Soils take thousands of years to develop and people depend on them for a huge part of their food supply.

“Explain the causes of soil degradation”

• Use p.116-120 of Planet Geography to answer this question.

• When you have finished, write a short paragraph to explain why soil erosion is of concern to farmers.

• This needs to be completed for h/w.