In irrigation engineering, the consumptive use of water (also called crop water use) for a standing crop is equal to which depth of water? Select the most complete description of the water components involved.

Introduction / Context:
Consumptive use of water (often denoted as ETc) is a core concept in irrigation engineering and agricultural water management. It represents the depth of water actually depleted from a cropped area and therefore must be replenished by irrigation or rainfall to sustain healthy growth. Understanding what exactly contributes to consumptive use helps in computing duty, scheduling irrigations, and designing canals and outlets.

Given Data / Assumptions:

• Standing crop under typical field conditions.
• Consumptive use is to be interpreted as depth over the cropped area.
• No special microclimate modifiers are specified; use standard agronomic meaning.

Concept / Approach:
Consumptive use equals the total evapotranspiration from the field. This includes two components: transpiration through plant stomata and evaporation from exposed surfaces. In cropped fields, evaporation occurs from both plant surfaces (canopy interception) and the adjacent soil surface. Hence, a complete definition must cover transpiration and both sources of evaporation.

Step-by-Step Solution:
1) Identify components: transpiration (T) and evaporation (E).2) Evaporation has two contributors: E_plant (from wet leaves) and E_soil (from bare soil between rows).3) Consumptive use depth CU = T + E_plant + E_soil.4) Compare options: the one including transpiration and evaporation from crop and adjacent soil is most complete.

Verification / Alternative check:
In FAO and standard irrigation texts, ETc is defined as the combined process of evaporation and transpiration. Field water balance methods and lysimeter measurements inherently capture soil evaporation as well as plant transpiration, confirming the comprehensive definition.

Why Other Options Are Wrong:

• Transpired only: ignores evaporation losses.
• Evaporated only: ignores the dominant plant transpiration component.
• Transpired and evaporated by the crop (plant surfaces only): omits soil evaporation between rows.
• None of the above: incorrect because one option precisely matches the standard definition.

Common Pitfalls:

• Confusing consumptive use with net irrigation requirement; the latter also accounts for effective rainfall and soil moisture change.
• Ignoring soil evaporation in wide-row crops or early growth stages when canopy cover is low.

Final Answer:
Used by the crop in transpiration and evaporation plus the water evaporated from the adjacent soil surface.