Question

If net irrigation for a crop is 8 cm and field efficiency is 75% then the gross irrigation depth to be applied will be

• A. 10.66 cm
• B. 6.00 cm
• C. 8.75 cm
• D. 12.00 cm

Hint:

Gross irrigation is always greater than net irrigation.
\( \text{Gross} = \frac{\text{Net}}{\text{Efficiency}} \).
If field efficiency is 75%, you must apply approximately 1.33 times the net requirement.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Gross irrigation depth ($d_g$) is the total depth of water applied to the field, which includes both the net water required by the crop ($d_n$) and the water lost to application inefficiencies (such as deep percolation and runoff).
Key Formula or Approach:
The relationship is given by:
\[ \text{Gross Irrigation Depth } (d_g) = \frac{\text{Net Irrigation Depth } (d_n)}{\text{Field Efficiency } (\eta_f)} \]

Step 2: Detailed Explanation:
Given values:
- Net irrigation depth ($d_n$) = $8 \text{ cm}$
- Field application efficiency ($\eta_f$) = $75\% = 0.75$
Substitute these values into the equation:
\[ d_g = \frac{8 \text{ cm}}{0.75} = 10.666... \text{ cm} \approx 10.66 \text{ cm} \]

Step 3: Final Answer:
The gross irrigation depth to be applied is 10.66 cm, corresponding to option (A).