This document discusses soils and soil formation. It describes soils as being made up of mineral particles, organic remains, water, and air. Soils can be divided into horizons including the O horizon of organic material, the A horizon where humus builds up, the B horizon where minerals and organic matter are deposited, and the C horizon of unaltered rock. The document also states that soil formation is influenced by climate, organisms, relief, parent material, and time according to Jenny's 1941 model of soil formation.

1. Topic 3: Human population, carrying
capacity and resource use
3.4: Soil System
Soil
More than just dirt

2. Topic 3: Human population, carrying
capacity and resource use
3.4: Soil System
Soils are:
• The part of the lithosphere where life
processes and soil forming processes both
take place.

3. Topic 3: Human population, carrying
capacity and resource use
3.4: Soil System
What is soil made from?
Soils can be thought of as being made up of four main
components.
• Mineral particles mainly from the underlying rock
• Organic remains that have come from the plants and animals
• Water within spaces between soil grains
• Air within the soils grains

4. Topic 3: Human population, carrying
capacity and resource use
3.4: Soil System
Soil profile

5. Topic 3: Human population, carrying
capacity and resource use
3.4: Soil System
The soil profile can be divided into HORIZONS
O - newly added organic material such as leaf litter
A - where in many soils humus builds up. Humus forms from partially
decomposed organic matter and often mixed with fine mineral
particles
B - the layer where soluble minerals and organic matter tends to be
deposited from the layer above by leaching. In particular clay and iron
salts can be deposited in this horizon
C - This layer is mainly unaltered rock from which the soil forms

6. Topic 3: Human population, carrying
capacity and resource use
3.4: Soil System
How do soils form?
• S = ƒ cl. o. r. p. t. . . .
• S = soil, cl = climate, o = organisms, r = relief (land
shape, topography), p = parent material, t = time
(Jenny: 1941)