5.1 Introduction to Soil Systems

Significant Ideas

• 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

1. The soil system may be illustrated by a soil profile that has a layered structure (horizons).

2. Soil system storages include organic matter, organisms, nutrients, minerals, air and water.

3. 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.

4. 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.

5. Transformations include decomposition, weathering and nutrient cycling.

6. 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.

7. A soil texture triangle illustrates the differences in composition of soils.

Applications and Skills

1. Outline the transfers, transformations, inputs, outputs, flows and storages within soil systems.

2. Explain how soil can be viewed as an ecosystem.

3. 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.

Guidance

1. Studies of specific soil profiles, such as podsol, are not required.

2. Familiarity with the soil texture triangle diagram used for soil type classification based on the percentage of sand, silt, and clay in the soil is required.

Key Vocabulary

• Soil

  • Sand

  • Silt

  • Clay

  • Loam

• Soil profile

  • Horizons

  • Organic material

  • Bedrock

• Erosion prevention

  • Cover crops

  • Terracing

  • Contour plowing

  • Wind breaks

• Soil quality/degradation

  • Leaching

  • Salinization

  • Irrigation

  • Fertilizers

  • Liming

  • Crop rotation

  • Fallowing

Textbook Reading and/or Activities

• Pages 236-244

  • To do (p.237)

  • ToK (p.238)

  • To do (p.243-244)

Notes

i-Biology Notes (Not available)

A detailed set of notes, created by Stephen Taylor, examining UX - UY and AX - AY.

i-Biology Study Questions (Not available)

A series of questions, created by Stephen Taylor, to help check your understanding of the IB learning expectations. This is VERY GOOD practice.

Bioknowledgy Notes (Not available)

A detailed set of notes, created by Chris Paine, examining all of the IB learning expectations.

Bioknowledgy Study Questions (Not available)

A series of questions, created by Chris Paine, to help check your understanding of the IB learning expectations. This is VERY GOOD practice.

Learning Activities

Soil Texture Triangle Activity

This worksheet, modified from the Northern Bedford County School District, will provide you with practice to improve your ability to read and interpret a soil texture triangle.

Determining Soil Texture

This site, by the Food and Agricultural Organization of the United Nations, walks through the process of determining a soil sample's texture. Use this to determine the texture of your sample.

Soil Systems

Try these questions to practice communicating your thoughts and responding to IB prompts.

Supplemental Reading