Water Requirement of Crops MCQ with answer and solution

Concept

Sub-surface irrigation needs good-quality water, because poor-quality water can clog the buried perforated pipes and add salts to the root zone.

Step-by-step solution

1. List the favourable conditions for sub-surface irrigation: permeable soil in the root zone, an impervious layer below, uniform topography, and good-quality water. 2. So the Assertion is true. 3. In artificial sub-surface irrigation, water flows through buried perforated or open-jointed pipes. 4. Bad-quality water (salts, silt, impurities) can deposit material and block these pipes. So the Reason is true. 5. Pipe blocking is a direct reason why good-quality water is needed, so the Reason explains the Assertion. Answer (A).

Explanation

Good-quality water is a standard favourable condition for sub-surface irrigation. In the artificial type, water moves through buried perforated pipes, and bad water can block these holes. So both statements are true, and the Reason explains the Assertion.

Why the other options are wrong

B: The Reason directly explains why good water is needed, so it is not unrelated. C: Both statements are actually true. D: The Reason is true, because pipe clogging by bad water is a known problem.

Shortcut

Buried pipes plus bad water means clogging, so good water is needed. Reason explains Assertion.

Common mistake

Choosing B by thinking salinity of the root zone is the only reason, and ignoring pipe clogging.