Question

Naturally formed aggregates are known as

• A. Crusts
• B. Concretions
• C. Flocculens
• D. Peds

Hint:

Remember the distinction:
Natural aggregates $\rightarrow$ Peds.
Artificial aggregates (tillage-induced) $\rightarrow$ Clods.
Precipitated mineral deposits $\rightarrow$ Concretions.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Soil structure is defined by the arrangement of primary soil particles (sand, silt, clay) into secondary units or aggregates.
These aggregates can form through natural pedogenic processes or artificial mechanical disturbances.

Step 2: Detailed Explanation:
The term Ped is used to describe a naturally occurring, relatively stable soil aggregate.
Peds are formed by wetting and drying cycles, freezing and thawing, root growth, and the cementing action of organic matter and microbial compounds.
The shape and arrangement of peds determine the structural class of the soil profile (such as granular, blocky, platy, or prismatic).
Let us examine the other options:
1. Crusts: These are compacted, thin surface layers formed when raindrops break down surface aggregates and dry into a hard, continuous sheet, which can inhibit seed germination.
2. Concretions: These are hard, local accumulations of chemical compounds (such as iron or manganese oxides) that precipitate from the soil solution over time.
3. Flocculens (or flocs): These are loose, temporary groupings of clay particles held together by weak electrostatic forces, representing the initial step before stable aggregates are formed.
4. Clods (not listed): These are artificial, irregular soil masses formed at the surface due to mechanical disturbances like tillage or plowing.

Step 3: Final Answer:
Naturally formed soil aggregates are called Peds, which corresponds to Option (D).