Soil–plant water relations: which statements about hygroscopic water, wilting point, field capacity deficit, and spatial variability are correct?

Introduction / Context:
Irrigation scheduling, drought assessment, and crop-water modelling require accurate terminology for soil water states. This question validates key definitions used by agronomists and hydrologists.

Given Data / Assumptions:

• Unsaturated soil with pellicular (adsorbed) water films on particles.
• Crop water stress relates to soil water availability.

Concept / Approach:
Hygroscopic water: tightly adsorbed (pellicular) water not available to plants.Wilting point: moisture content at which plants cannot extract sufficient water and wilt permanently.Soil moisture deficiency: water depth required to bring soil back to field capacity from current state.Spatial variability: texture, structure, rooting depth, and microtopography cause differing deficits across a field.

Step-by-Step Solution:

Verification / Alternative check:
Standard soil science texts and FAO irrigation guidelines use the same definitions, corroborating all statements.

Why Other Options Are Wrong:
Choosing any single statement would ignore that all listed statements are valid, so the most comprehensive choice is correct.

Common Pitfalls:

• Confusing field capacity with saturation.
• Assuming uniform moisture deficit across heterogeneous soils.
• Believing hygroscopic water contributes meaningfully to transpiration.

Final Answer:
All the above