Question

Determine the gross irrigation requirement of the crop, if the field capacity of soil is 18 cm, water content in the root depth before irrigation is 12 cm, and peak consumptive use rate is 70 mm/day assuming the irrigation efficiency as 80%.

• A. 7.5 cm
• B. 75 cm
• C. 49 cm
• D. 4.9 cm

Hint:

Gross irrigation requirement = Net requirement Irrigation efficiency.
Irrigation efficiency accounts for losses (evaporation, seepage, runoff).
Typical irrigation efficiencies: surface (40-60%), sprinkler (60-80%), drip (80-90%).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Gross irrigation requirement is the total water that needs to be applied to meet the crop's water demand, considering irrigation efficiency.

Step 2: Key Formula or Approach:
Net irrigation requirement = Field capacity - Current moisture content
Gross irrigation requirement = Net irrigation requirement Irrigation efficiency

Step 3: Detailed Explanation:
Given:
Field capacity (FC) = 18 cm
Current moisture content = 12 cm
Irrigation efficiency = 80% = 0.8
Net irrigation requirement = FC - Current moisture = 18 - 12 = 6 cm
Gross irrigation requirement = Net requirement Efficiency = 6 0.8 = 7.5 cm
The peak consumptive use rate (70 mm/day) is not needed for this calculation.
Thus, the gross irrigation requirement is 7.5 cm.

Step 4: Final Answer:
Thus, the gross irrigation requirement is 7.5 cm.
[0.5cm]