Formation & importance of soils, lecture 27 Flashcards
Soil
The outermost layer of the Earth
How is soil formed?
Weathering of rocks
Phrase to describe soil
‘living mantle of the Earth’
Is soil a renewable or non-renewable resource?
non-renewable resource
Rough soil formation time
thousands of years to form
Soils are at the interfere of
4
- Lithosphere
- Atmosphere
- Hydrosphere
- Biosphere
Soils at the interface of
the Lithosphere
Soils formed from rock constituents.
Soils formed from rock constituents.
the atmosphere
Air overlies and intermingles with soil.
Soils are at the interface of
the hydrosphere
Water flows through soil.
Soils are at the interface of
the biosphere
Biota live in and on soil.
Soil science is…
interdisciplinary
Key functions of soil
6
(according to DEFRA)
- Food and Fibre Production
- Environmental Interaction
- Support of Ecological Habitat and Biodiversity
- Protection of Cultural Heritage
- Providing a platform for construction
- Providing Raw Materials
There is unlocked potential in soil resources for…
biological and medical resources
Regulation of water by soil,
Soil misuse or over-exploitation can have significant consequences for…
example?
groundwater, rivers, estuaries and coastal waters
eg: overuse of fertilisers
Link of soil to history
Dominant nations had good soil,
facilitates productive agriculture
Soils quality reflects
3 aspects
all chemical physical biological properties
Main threats to soil function and quality
5
- Erosion
- Compaction and sealing
- Contamination
- loss of SOM (Soil organic matter)
- Salinisation
Threats to soil function and quality
Erosion
(landslides)
loss of productivity and biodiversity
used linked to overuse
Threats to soil function and quality
Compaction and sealing
intensive use of heavy equipment or grazing whilst the soil is saturated
(loss of biodiversity, flooding)
Threats to soil function and quality
contamination
Metals and organic contaminants could degrade soil quality and functions, implications for the wider environment
Threats to soil function and quality
loss of SOM
Loss of SOM, loss of fertility, increased risk of erosion, also reduces water retention capacity, linked to climate change
Threats to soil function and quality
Salinisation
- Excess accumulation of soluble salts due to saline water use in farming or irrigation practices
- generally in hotter countries, Middle East
Percentage of the World’s freshwater stored in soil for plant use
66%
How should soil be viewed?
as a finite resource
Weathering
Physical and chemical breakdown of rocks and other materials
Soils relate to what
the rock they originate from
Factors controlling soil formation
5
- parent material
- climate
- biota
- topography
- time
Factors affecting soil formation
parent material
unconsolidated material or rock in which soil development occurs
2 examples of parent material deposits
organic deposits - peat
glacial ice transport - glacial till
Example of parent material
organic deposits - peat
Organic material deposited when accumulation exceeds decomposition: stratified deposit of peat.
Example of parent material
glacial ice transport - glacial till
Glacial till, material deposited directly by ice, is a heterogeneous (unstratified) mixture of rounded boulders, stones, sand, silt, and clay.