- The soil system is a dynamic ecosystem that has inputs, outputs, storages and flows.
- The quality of soil influences the primary productivity of an area.
Knowledge and understanding:
- The soil system may be illustrated by a soil profile that has a layered structure (horizons).
- Soil system storages include organic matter, organisms, nutrients, minerals, air and water.
- Transfers of material within the soil, including biological mixing and leaching (minerals dissolved in water moving through soil), contribute to the organization of the soil.
- There are inputs of organic material including leaf litter and inorganic matter from parent material, precipitation and energy. Outputs include uptake by plants and soil erosion.
- Transformations include decomposition, weathering and nutrient cycling.
- The structure and properties of sand, clay and loam soils differ in many ways, including mineral and nutrient content, drainage, water-holding capacity, air spaces, biota and potential to hold organic matter. Each of these variables is linked to the ability of the soil to promote primary productivity.
- A soil texture triangle illustrates the differences in composition of soils.
Applications and skills:
- Outline the transfers, transformations, inputs, outputs, flows and storages within soil systems.
- Explain how soil can be viewed as an ecosystem.
- Compare and contrast the structure and properties of sand, clay and loam soils, with reference to a soil texture diagram, including their effect on primary productivity.
- Significant differences exist in arable (potential to promote primary productivity) soil availability around the world. These differences have socio-political, economic and ecological influences.
Theory of knowledge:
- The soil system may be represented by a soil profile—since a model is, strictly speaking, not real, how can it lead to knowledge?
- Communities and ecosystems (2.2)
- Flows of energy and matter (2.3)
- Investigating ecosystems (2.5)
- Biomes, zonation and succession (2.4)
- Introduction to water systems (4.1)
- Terrestrial food production systems and food choices (5.2)
- Soil degradation and conservation (5.3)
- Acid deposition (6.4)
- Climate change (7.1 and 7.2)
- Resource use in society (8.2)
- Solid domestic waste (8.3)