10 Questions
What is the main difference between PEDS and CLOD?
PEDS are natural aggregates while CLOD is an artificially formed soil mass
Which type of soil structure has thin horizontal plates that are larger in the horizontal axis than the vertical axis?
Plate-Like (Platy)
In what type of soil structure does the vertical axis resemble a pillar?
Columnar
When the tops of the vertical aggregates are rounded, what is the term used to describe this structure?
Columnar
Which type of soil structure has three dimensions that are about the same size?
Prismatic Block-Like
What is the term used for soil structure with six-faced blocks and sharp angular edges?
1
In which type of soil structure are the faces and edges mainly rounded?
Subangular Blocky
Where is Platy structure most noticeable?
Surface layers of virgin soils
What gives rise to Platy structure according to the text?
Parent material and action of water or ice
Where do Prism-Like structures commonly occur?
Subsoil horizons of Arid and Semi-Arid Regions
Study Notes
Soil Structure
- Soil structure refers to the arrangement and organization of primary and secondary particles in a soil mass.
- Soil properties like water movement, heat transfer, aeration, and porosity are influenced by soil structure.
Significance of Soil Structure
- Soil structure controls the amount of water and air present in soil.
- Plant roots and germinating seeds require sufficient air and oxygen for respiration.
Formation of Soil Structure
- Soil particles are present as single individual grains and as aggregates (groups of particles bound together into granules or compound particles).
- Particles in sandy and silty soils are present as single individual grains, while in clayey soil they are present in granulated conditions.
Classification of Soil Structure
- Primary particles (sand, silt, and clay) usually occur grouped together in the form of aggregates.
- Spherical (spheroidal) structure: rounded aggregates (peds) that are loosely arranged and readily separated.
- Spherical structure allows for good infiltration, percolation, and aeration.
Factors Affecting Soil Structure
- Climate: arid regions have little aggregation of primary particles, while semi-arid regions have a greater degree of aggregation.
- Organic matter: improves soil structure.
- Tillage: breaks down large clods into smaller fragments.
- Microbes: algae, fungi, and actinomycetes help keep soil particles together.
Soil Structure Types
- Plate-like (platy) structure: aggregates arranged in thin horizontal plates.
- Prism-like structure: vertical axis is more developed than horizontal, giving a pillar-like shape.
- Block-like structure: aggregates are reduced to blocks with all three dimensions about the same size.
Subcategories of Block-like Structure
- Angular blocky: faces are flat and distinct, edges are sharp and angular.
- Subangular blocky: faces and edges are mainly rounded.
Test your knowledge about the arrangement and organization of primary and secondary particles in a soil mass, known as soil structure, and its importance in influencing soil properties like water movement, heat transfer, and aeration. Explore how soil structure controls the amount of water and air present in soil and its impact on plant roots and germinating seeds. Learn how cultivation and tillage operations can modify soil structure.
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