Step 1: Understand the IW/CPE ratio method for irrigation scheduling.
IW/CPE stands for Irrigation Water / Cumulative Pan Evaporation. It's a ratio used to decide when to irrigate. Irrigation is applied when the cumulative pan evaporation reaches a certain level relative to the depth of irrigation water applied. A lower ratio (e.g., 0.6) means the crop can tolerate more evaporative loss before needing water (more drought tolerant), while a higher ratio (e.g., 0.9) means the crop needs water more frequently.
Step 2: Match each crop with its typical IW/CPE ratio.
- C. Cotton: It has a deep root system and is relatively drought-tolerant. It would have the lowest IW/CPE ratio among the options. Match C with III. 0.6.
- D. Barley: A winter cereal with moderate water requirements. Match D with IV. 0.75.
- A. Sorghum: A summer cereal that is more drought-tolerant than maize but requires more water than barley or cotton. Match A with I. 0.8.
- B. Maize: A summer cereal that is very sensitive to water stress and has high water requirements. It would have the highest IW/CPE ratio. Match B with II. 0.9.
Step 3: Compile the correct pairings.
The correct pairings are: A-I, B-II, C-III, D-IV. This corresponds to option (A).