IB Environmental systems and societies Topic 5.1C Soil Texture Revision Notes (SL/HL)

IB Environmental systems and societies Topic 5.1C Soil Texture Revision Notes (SL/HL) | RevisionDojo

Written by official IB examiners

Soil Texture Controls How Soil Holds Water and Nutrients

Definition

Soil texture

Soil texture refers to the relative proportions of sand, silt, clay, and humus in a soil sample.

Texture is the proportion of sand, silt, and clay in a soil.
It governs drainage, aeration, nutrient-holding capacity, structure, and ease of cultivation.

Example

Gritty, coarse soil is sand-rich, while a smooth, flour-like feel signals high silt.

The Components of Soil Texture

Component	Particle size	Characteristics	Examples
Sand	Largest (0.05 to 2.0 mm)	Drains quickly, poor water retention, good aeration	Beach sand, desert soils
Silt	Medium (0.002 to 0.05 mm)	Retains water better than sand, smooth texture	River sediments, loamy soil
Clay	Smallest (less than 0.002 mm)	High water retention, poor drainage, compact when wet	Mud, wetland soil
Humus	Varies	Organic matter, improves fertility, absorbs moisture	Decomposed plant and animal material

A loam blends sand, silt, clay, and humus in balanced proportions, which is why it is the best all-round agricultural soil.

Determining Soil Texture

Feel Test (Field Method)

Rub moist soil between your fingers: gritty means sand, smooth means silt, and sticky and plastic means clay.
It is quick and useful in the field but gives no precise percentages.

Hint

Add a little water before rubbing the soil.
Moisture makes the difference between sand, silt, and clay much easier to feel.

Sedimentation Test (Laboratory Method)

Shake soil in water in a measuring cylinder so the particles separate by size, then let them settle.
Sand settles first (minutes), then silt (1 to 2 hours), and clay last (24 to 48 hours).

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Soil Texture Controls How Soil Holds Water and Nutrients

Definition

Soil texture

Soil texture refers to the relative proportions of sand, silt, clay, and humus in a soil sample.

Texture is the proportion of sand, silt, and clay in a soil.
It governs drainage, aeration, nutrient-holding capacity, structure, and ease of cultivation.

Example

Gritty, coarse soil is sand-rich, while a smooth, flour-like feel signals high silt.

The Components of Soil Texture

Component	Particle size	Characteristics	Examples
Sand	Largest (0.05 to 2.0 mm)	Drains quickly, poor water retention, good aeration	Beach sand, desert soils
Silt	Medium (0.002 to 0.05 mm)	Retains water better than sand, smooth texture	River sediments, loamy soil
Clay	Smallest (less than 0.002 mm)	High water retention, poor drainage, compact when wet	Mud, wetland soil
Humus	Varies	Organic matter, improves fertility, absorbs moisture	Decomposed plant and animal material

A loam blends sand, silt, clay, and humus in balanced proportions, which is why it is the best all-round agricultural soil.

Determining Soil Texture

Feel Test (Field Method)

Rub moist soil between your fingers: gritty means sand, smooth means silt, and sticky and plastic means clay.
It is quick and useful in the field but gives no precise percentages.

Hint

Add a little water before rubbing the soil.
Moisture makes the difference between sand, silt, and clay much easier to feel.

Sedimentation Test (Laboratory Method)

Shake soil in water in a measuring cylinder so the particles separate by size, then let them settle.
Sand settles first (minutes), then silt (1 to 2 hours), and clay last (24 to 48 hours).

Definition

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(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

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Duis aute irure dolor in reprehenderit

Note

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Tip

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Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
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Topic 1: Foundation 3 subtopics

Topic 2: Ecology5 subtopics

Topic 3: Conservation and biodiversity3 subtopics

Topic 4: Water4 subtopics

Topic 5: Land2 subtopics

Topic 6: Atmosphere and climate change4 subtopics

Topic 7: Natural resources3 subtopics

Topic 8: Human populations and urban systems3 subtopics

HL lenses 3 subtopics

IB Environmental systems and societies 5.1C Soil Texture Notes

Topic 1: Foundation 3 subtopics

Topic 2: Ecology5 subtopics

Topic 3: Conservation and biodiversity3 subtopics

Topic 4: Water4 subtopics

Topic 5: Land2 subtopics

Topic 6: Atmosphere and climate change4 subtopics

Topic 7: Natural resources3 subtopics

Topic 8: Human populations and urban systems3 subtopics

HL lenses 3 subtopics

Soil Texture Controls How Soil Holds Water and Nutrients

The Components of Soil Texture

Determining Soil Texture

Feel Test (Field Method)

Sedimentation Test (Laboratory Method)

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Soil Texture Controls How Soil Holds Water and Nutrients

The Components of Soil Texture

Determining Soil Texture

Feel Test (Field Method)

Sedimentation Test (Laboratory Method)

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account