Human Population, Carrying Capacity, and Resource Use

3.4 The Soil System

Assessment Statements3.4.1 Outline how soil systems integrate

aspects of living systems.3.4.2 Compare and contrast the structure and

properties of sand, clay and loam soils, including their effect on primary productivity.

3.4.3 Outline the processes and consequences of soil degradation.

3.4.4 Outline soil conservation measures3.4.5 Evaluate soil management strategies in a

named commercial farming system and in a named subsistence farming system.

Soil provides……

1. Medium for plant growth – most food is grown in soil.

2. Stores freshwater.3. Filters water.4. Nutrient recycling (breakdown of organic matter)5. Habitat for microorganisms and animals. (goods and services: food webs, antibiotics)6. Provides raw materials: peat, clay, sand, gravel

and minerals

3.4.1 Outline how soil systems integrate aspects of living systems.

Soils are a major component of the world’s ecosystems.

They link the atmosphere, lithosphere (rocks), biosphere (living matter), and hydrosphere (water).

Soil is comprised of weathered bedrock, organic matter, air, and water.

3.4.1 Outline how soil systems integrate aspects of living systems.

Soil forming process consists of: Gains and losses of material to and from the profile Movement of water between horizons Chemical transformation within each horizon

So…soils are open systems in a steady-state equilibrium. Soils are vital to humans, but take a long time to develop.

So….a non-renewable resource

3.4.2 Compare and contrast the structure and properties of sand, clay and loam soils, including their effect on primary productivity.

• Sand– Mineral Content: Low– Drainage: High– Water-holding capacity: Low– Air spaces: High– Biota: Low– Potential to hold organic

matter: Low– Primary Productivity: Low

3.4.2 Compare and contrast the structure and properties of sand, clay and loam soils, including their effect on primary productivity.

• Clay– Mineral Content: High– Drainage: Low– Water-holding capacity:

High– Air spaces: Low– Biota: High to Medium– Potential to hold organic

matter: High to Medium– Primary Productivity:

Quite Low

3.4.2 Compare and contrast the structure and properties of sand, clay and loam soils, including their effect on primary productivity.

• Loam– Mineral Content: Medium– Drainage: Medium– Water-holding capacity:

Medium– Air spaces: Medium– Biota: Medium to High– Potential to hold organic

matter: Medium to High– Primary Productivity: High

3.4.3 Outline the processes and consequences of soil degradation.

• Soil Degradation – Decline in quantity and quality of soil

• Issues around it:– Water and Wind erosion– Acidification (Toxic metals)– Eutrophication (Nutrient

Enrichment)– Salinization (Too much salt)– Soil pollution– Desertification

3.4.3 Outline the processes and consequences of soil degradation.

• Factors of erosion:– Erosivity (Rainfall totals,

intensity, and seasonal distribution)

– Erodibility (Susceptibility to erosion)– Slope length and gradient – Cover and management

(Crop and cultivation practices)

– Erosion control practice (Soil conservation measures)

3.4.3 Outline the processes and consequences of soil degradation.• Consequences of soil degradation:– Erosion: reduced crop growth and yields, loss of soil fertility– Salinization (Too much salt): Stunts crop growth, Lowers crop

yields, Destroys fertility and plants, Damage to infrastructure, Reduction of water quality

– Desertification: Economic loses, Lower living standards, Major threat to biodiversity, Prolonged droughts

3.4.4 Outline soil conservation measuresMechanical methods to reduce water flow•Contour Plowing – Takes advantage of ridges formed at right angles to the slope to slow water•Terracing – Slope is broken up into a series of flat steps with raised levees at the edge.•Land around gullies and ravines can be fenced off and planted with small trees.•Check dams can be used to slow water in gullies.

3.4.4 Outline soil conservation measuresCropping and soil husbandry methods against wind and water damage•Maintaining a crop cover as long as possible (ex. multi-cropping)•Keeping crop stubble and roots after harvesting•Planting a grass crop: roots bind the soil.

3.4.4 Outline soil conservation measures

Management of salt-affected soils•Flush the soil with water to leach the salt away•Apply chemicals (Ex. Gypsum/calcium sulfate – replaces sodium ions on clay and colloids with calcium ions.)•Reduce evaporation losses (compost cover)- less upward movement of water in soil

3.4.5 Evaluate soil management strategies in a named commercial farming system and in a named subsistence farming system.• Do this with the

reading. If there is time, we will talk about this as a class.