Correct option is C
The correct answer is: (C) Exchangeable acidity is derived from exchangeable Al³⁺ cations
Explanation:
Exchangeable acidity in soil refers to the acidity caused by exchangeable hydrogen (H⁺) and aluminum (Al³⁺) ions present in the soil colloid complex.
It is primarily due to exchangeable Al³⁺ cations, which can hydrolyze and release hydrogen ions (H⁺) into the soil solution, increasing soil acidity.
Aluminum plays a crucial role in acidic soils (pH < 5.5) by contributing to soil acidity through its hydrolysis reaction, forming Al(OH)²⁺ and releasing additional H⁺ ions.
Information Booster:
Higher levels of exchangeable Al³⁺ indicate a need for lime application to neutralize acidity.
Exchangeable Al³⁺ can be toxic to plants, inhibiting root growth and reducing crop productivity.
It is different from active acidity (H⁺ in soil solution) and residual acidity (H⁺ and Al³⁺ bound to organic matter and clay particles).
Knowledge Booster :
Exchangeable Na⁺ cations → they are associated with alkaline or sodic soils.
Exchangeable Ca³⁺ cations → Calcium (Ca²⁺, not Ca³⁺) is a basic cation that reduces soil acidity.
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