The characteristics of the Plinthite horizon are:

[a] It is rich in humus

[b] It is rich in sesquioxide

[c] Presence of yellowish or greyish mottles

[d] Hardens reversibly due to repeated wetting and drying

Choose the correct answer from the options given below:

Correct option is B

Correct option: (b) — (b) and (c) only

Why option (2) is correct:
· (b) Rich in sesquioxide
· Plinthite is enriched with iron and aluminium oxides (sesquioxides).
· These accumulate due to repeated reduction–oxidation processes in seasonally waterlogged soils.
· (c) Presence of yellowish or greyish mottles
· Plinthite horizons commonly show red, yellow, or grey mottling.
· Mottles are diagnostic features formed due to fluctuating water tables and Fe movement.
❌ Why other statements are incorrect
· (a) It is rich in humus
· Incorrect.
· Plinthite is a subsurface horizon and is poor in organic matter.
· (d) Hardens reversibly due to repeated wetting and drying
· Incorrect.
· Plinthite hardens irreversibly on repeated wetting and drying, forming petroplinthite.
· The statement says reversibly, which makes it wrong.
�� Key Points to Remember
· Plinthite forms in tropical and subtropical climates.
· Rich in Fe–Al sesquioxides.
· Shows distinct mottling due to alternating redox conditions.
· On repeated wetting–drying, it hardens irreversibly.