5.1 Introduction to Soil Systems
Significant Ideas:
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The soil system is a dynamic ecosystem that has inputs, outputs, storages and flows.
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The quality of soil influences the primary productivity of an area.
Knowledge and Understandings:
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The soil system may be illustrated by a soil profile that has a layered structure (horizons).
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Soil system storages include organic matter, organisms, nutrients, minerals, air and water.
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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.
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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.
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Transformations include decomposition, weathering and nutrient cycling.
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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.
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A soil texture triangle illustrates the differences in composition of soils.
Application and Skills:
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Outline the transfers, transformations, inputs, outputs, flows and storages within soil systems.
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Explain how soil can be viewed as an ecosystem.
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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.
International-mindedness:
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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:
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The soil system may be represented by a soil profile—since a model is, strictly speaking, not real, how can it lead to knowledge?