Question

Given below are two statements, one labelled as Assertion (A) and the other labelled as Reason (R).
Assertion (A): Addition of organic matter to a mineral soil leads to improvement in water holding capacity of the soil.
Reason (R): Under tropical conditions, water holding properties and available water range of a mineral soil due to addition of organic matter may not change materially.
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A).
• B. Both (A) and (R) are correct but (R) is NOT the correct explanation of (A).
• C. (A) is correct but (R) is not correct.
• D. (A) is not correct but (R) is correct.

Hint:

Check whether the reason genuinely explains the assertion, or whether it actually describes an exception to it.

Answer 1

The Correct Option is B

This is an assertion-reason question, so the first job is to check each statement on its own before asking whether one explains the other.

1. Assertion (A): This is the standard rule taught in soil science, organic matter added to a mineral soil raises its water holding capacity by adding absorbent surfaces and improving soil structure. Taken broadly, this is true.
2. Reason (R): This is a narrower, region specific finding, in tropical mineral soils, which are often rich in low activity clays and oxides, adding organic matter does not always change the water holding properties or available water range by much. Research from tropical soils backs this up, so (R) is also true.

The catch is that (R) does not build a case for why (A) is true, it actually describes a setting where the improvement described in (A) barely shows up. A reason that contradicts the general trend of the assertion cannot be called its explanation.

Let's summarize:

• Both statements are correct when read as independent facts.
• (R) describes an exception in tropical soils rather than the mechanism behind (A), so it fails to explain (A).

That makes the answer option 2, both (A) and (R) correct, but (R) is not the correct explanation of (A).