The ratio between the area of crop irrigated and the quantity of water applied to the crop is termed as: (RJ AO 2011)

✅Explanation: In irrigation engineering, "duty" refers to the area of land that can be irrigated with a unit volume of water. It represents the relationship between the volume of water used and the area of land irrigated. A higher duty means that a larger area can be irrigated with the same amount of water, indicating greater water use efficiency.

📌 Other option explanations:
-Option B: Delta: Delta refers to the total depth of water required by a crop during its entire growth period. It is usually expressed in centimeters or inches.
-Option C: Base period: Base period is the time interval between two consecutive irrigations. It is influenced by factors like crop type, climate, and soil characteristics.