1. Soil: “No soil, NO planet Earth”
Mr R & Ms G
Soil: “No soil, NO planet Earth”
Soil involves numerous connections with physical, chemical and biological processes.
For thousands of years soil has been a perfect example of how humans interact and need the Earth to survive. Agriculture, cultivation and farming have all existed because of soils.
The ability to understand and investigate soil has led to population growth and feeding the world’s population in areas of the planet with decreased fertility.

2. Soil Terminology
Soil profile – the view of all layers/horizons in the soil. The profile contains the O, A, B, C and Bedrock layers.
Shows the thickness of soil, color and chemical composition of soil and relative age (mature or immature) of the soil.
Soil Horizon – layers or zones of soil. Separated by different colors, textures, and structure. O, A, B, C and R (parent rock/bedrock)
Top soil – A combination of the O and A horizon. Valuable assets for growth of plants and agriculture.
Contains organic material, humus (dead or decaying material) and habitats fro animals.

3. Soil Terminology Organic matter: part of the O and A horizon
Living material
Root system
Provides nutrients and chemicals to and from the soil
Sub soil:
B Horizon
less organic material present
Limit of borrowing animals
- Zone of accumulation (nutrients and leeching)
Soil particles:
-soil is made of 3 main particles – SAND, SILT and CLAY. These are characterized by their particle size and absorption of different chemicals.

4. Soil Terminology
Humus – dead or decaying matter. Located in the O and A horizon
Parent material – A layer of rock which is the beginning of the soil formation process. This rock layer would be changed and broken down by physical and chemical weathering to create weathered material. (C horizon)
Bedrock – a layer of rock which is beneath the soil horizons and produces a natural barrier for percolating water (groundwater) and a base for the formation of soil.
Weathered material – material which comes from the parent rock or bed rock. This is broken down by physical and chemical weathering over a long period of time.

5. Soil Composition

7. Soil Formation

8. Soil Formation - Factors
Plants & Animals
Contains organic matter
Recycling of nutrients
Bacteria (nitrogen cycle)
Creates soil fertility
Slope
Surface runoff
Leeching and percolation rates
Parent Material
Develops from parent material
Undergoes physical and chemical weathering to change the rock into soil
Time
Takes time to weathering and change the soil
Longer time – thicker more developed soil
Climate
temperature and precipitation
Develops different types of soil
Amount of leeching

9. Soil Profile
The soil profile is the different zones or layers starting at the surface and moving vertically down to the bedrock or parent rock
Top soil is made up of two distinct layers/zones – O horizon and A horizon.
O horizon:
consists of the first 2 inches of soil.
Organic material (plant litter, animals)
A horizon:
Mixture of minerals, organic matter and humus

10. Soil Profile Subsoil contains the following: B Horizon:
Zone of fine clay – brought down from the A horizon
Some biological roots – this is the lowest point of tree roots
Zone of accumulation – shown by the color. Bright colors represent more movement of minerals from the top soil.
Little humus or organic matter
Above the C horizon

11. C horizon:
Contains parent material
Larger rocks and sediments
Mostly regolith – not soil
Clear difference between the B and C horizon – color and composition
First layer to be developed from the underlying bedrock or parent material.

12. Soil Texture Soil consists of 3 parts: Sand – 0.05-2mm
Different levels of sand between fine and coarse.
Silt – mm diameter
Helps move water through the soil
Clay – Less than 0.002mm in diameter
smallest particle size
Loam – an ideal mixture of sand, silt and clay create an ideal and fertile soil