Question

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R
Assertion A : Mulch conserves soil moisture
Reason R : Mulches cut off solar radiation falling on soil surface and reduce evaporation
In light of the above statements, choose the correct answer from the options given below

• A. Both A and R are true and R is the correct explanation of A
• B. Both A and R are true but R is NOT the correct explanation of A
• C. A is true but R is false
• D. A is false but R is true

Hint:

Mulch is essentially an "insulator" for the soil.
Less heat from the sun = Less energy for water to evaporate.
This is a "Classic" Soil Science question. Mulching $\rightarrow$ Reduction in Evaporation.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question tests the conceptual understanding of how mulching acts as a moisture conservation technique. It requires determining if the assertion and reason are true and if the reason logically explains the assertion.
Detailed Explanation:

• Evaluating Assertion A:
Mulch refers to any material (straw, leaves, plastic, etc.) spread over the soil surface.
It is a well-established fact in agronomy that mulching significantly reduces water loss from the soil, thus conserving moisture for plant use.
Statement A is true.

• Evaluating Reason R:
Evaporation is an energy-dependent process. It requires heat (latent heat of vaporization) and a vapor pressure gradient.
By covering the soil, mulches act as a physical barrier. They reflect a portion of solar radiation (increasing albedo) and shield the soil surface from direct sunlight.
This keeps the soil temperature lower and breaks the wind-surface interface, which drastically reduces the rate at which water molecules escape as vapor.
Statement R is true.

• Checking the Logical Link:
Why does mulch conserve moisture (A)? Because it reduces the energy input from solar radiation and creates a barrier against evaporation (R).
The Reason R provides the fundamental physical mechanism behind Assertion A.

Step 2: Final Answer:
Both statements are accurate, and the reason correctly explains the phenomenon described in the assertion.