Definition of waterlogging in irrigation practice: A tract is declared water-logged when which condition is met?

Introduction / Context:
Waterlogging is a critical hazard in irrigated agriculture. It reduces soil aeration, impairs root respiration, and lowers yields. The operational definition focuses on the position of the water table relative to the crop root zone.

Given Data / Assumptions:

• Root zone depth varies by crop and soil but is typically the top 0.6–1.5 m.
• Prolonged saturation in this zone is the key criterion.

Concept / Approach:
If the water table rises sufficiently to keep the root zone near-saturated, oxygen diffusion is limited, and toxic conditions develop. Hence, waterlogging is defined with respect to the root zone rather than a fixed depth such as 40 or 50 cm, which may not universally apply.

Step-by-Step Solution:
Identify the agronomic criterion: position of water table within root zone.Reject fixed-depth definitions as crop- and soil-dependent.Select option (c).

Verification / Alternative check:
Guidelines specify critical depths (e.g., < 1–1.5 m below ground) as warning thresholds, adjusted for crop rooting depth; thus the root-zone criterion is general.

Why Other Options Are Wrong:

• (a) and (b) are arbitrary depths; not universally valid.
• (d) cannot be right because (a) and (b) are not general definitions.

Common Pitfalls:
Using a single depth threshold for all crops; neglecting seasonal variability and soil textural effects on aeration.

Final Answer:
The crop root zone remains saturated (water table rises into root zone)