Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R
Assertion A : Soils of North-East India are primarily acidic in nature.
Reason R : Among others, the most common element in the soils of North-East India is 'Ca', which contributes towards acidity of the soil.
In light of the above statements, choose the correct answer from the options given below
Assertion A : Soils of North-East India are primarily acidic in nature.
Reason R : Among others, the most common element in the soils of North-East India is 'Ca', which contributes towards acidity of the soil.
In light of the above statements, choose the correct answer from the options given below
Show Hint
Acidic cations (Al, H, Fe) = Low pH (Acidic).
NE India has "Acidic" soils, while arid regions like Rajasthan have "Alkaline" soils.
- Both A and R are true and R is the correct explanation of A
- Both A and R are true but R is NOT the correct explanation of A
- A is true but R is false
- A is false but R is true
The Correct Option is C
Solution and Explanation
This is an Assertion-Reason type question evaluating knowledge of soil chemistry and regional soil characteristics in India.
Step 2: Detailed Explanation:
• Evaluating Assertion A: Soils in North-East India are indeed primarily acidic. This is due to the very high annual rainfall in the region.
• High precipitation causes intense leaching of basic cations (like Calcium, Magnesium, and Potassium) from the topsoil.
• As these bases are removed, they are replaced by acidic ions like $H^+$ and $Al^{3+}$, leading to low pH values (often between 4.5 and 5.5).
• Therefore, Assertion A is True.
• Evaluating Reason R: Calcium ($Ca$) is a basic cation (alkaline earth metal).
• In soil science, the presence of Calcium increases the soil pH (reduces acidity). This is why agricultural lime ($CaCO_3$) is added to acidic soils to neutralize them.
• The claim that 'Ca' contributes to soil acidity is chemically incorrect. Acidity in NE Indian soils is primarily due to Aluminium and Hydrogen ions.
• Therefore, Reason R is False.
Final Answer:
Assertion A is a correct statement regarding the regional soil characteristics, but Reason R is scientifically false as Calcium is an alkalizing agent, not an acidifying agent.
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