Soils

Soil is the thin layer of material on the earth's surface that is formed from the weathering of rocks and build up of organic material[1]. Soil is made of mainly mineral particles, organic materials, air, water and living organisms. These components of soil interact[1] which forms the basis of soil processes.

Soil and soil productivity is crucial to the survival and functioning of ecosystems, as plants depend on soil for nutrients and growth.

Quick facts

There is more carbon

stored in soil than in above ground vegetation[2].

Soil is a valuable resource that supports ecosystems and ecosystem processes. It forms over time into a soil profile, which contains horizons:

• A horizon - the humus rich topsoil, where nutrients and organic matter are the highest. It is also where biological activity is the highest - with plant roots, earthworms, insects and micro-organisms.
• B horizon - the subsoil. This horizon holds less organic material and usually holds more water, and typically has more clay.
• C horizon - the underlying weathered rock in hillslope soils or other underlying materials lacking soil development (in alluvial soils)
• O horizon - this layer sometimes accumulates on the soil surface, and is formed from plant litter[1].

Soils are continuously forming, through the gradual breakdown of rocks by weathering - which can be physical, chemical or biological. Soils also form from accumulation of material through the action of water (alluvial soils), wind (aeolian formed soils) and gravity (colluvial soils). Factors that can affect the formation of soil include the parent material, living organisms, climate (impacting the rate of decomposition and weathering), topography and time.

Soils properties are strongly influenced by the parent material (or rock) they are formed from - granite usually breaks down to be sandy and infertile soil, while many basalts break down to form fertile, clay soils.

Links and References

Salinity (substrate)

Substrate composition

Substrate consolidation

Substrate grain size

Geology and lithology

Soils explained - Queensland Government

Version 5 of Queensland Acid Sulfate Soil Technical Manual, Soil Management Guidelines

Soil Science Australia

Pages under this section

References

1. ^ a b c Queensland, , AU & o=The State of, How soils form | Soils explained. [online] Available at: https://www.qld.gov.au/environment/land/management/soil/soil-explained/forms [Accessed 13 September 2023].
2. ^ 'Soil as Carbon Storehouse: New Weapon in Climate Fight?'. [online] Available at: https://e360.yale.edu/features/soil_as_carbon_storehouse_new_weapon_in_climate_fight [Accessed 19 September 2023].

Last updated: 11 September 2023