Question

According to Kung (1971), water requirement to raise nursery for 1 ha irrigated rice crop is

• A. 40 mm
• B. 40 cm
• C. 10 cm
• D. 200 mm

Hint:

The nursery is small in area but is flooded daily for weeks, so express its water use as a depth over the main field.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
Before transplanting, rice seedlings are raised on a small nursery bed, and this bed needs its own water supply, separate from the main field. Kung (1971) worked out how much water this nursery stage needs, expressed against a 1 ha main field that will later be transplanted.

Step 2: Key Formula or Approach:
A rice nursery is usually only about one tenth of the main field area, but it is kept with standing water for the whole 25 to 30 day raising period, so its water use per unit area is high even though its total area is small.

Step 3: Detailed Explanation:
Kung (1971) reported this nursery stage water need, once expressed as a depth over the 1 ha main field, works out to about 200 mm.
This is far less than the total seasonal water need of the transplanted crop, which can run to over a meter, because the nursery occupies only a small patch of land even though it needs frequent watering.
Option 1 (40 mm) and option 3 (10 cm, that is 100 mm) understate this figure, and option 2 (40 cm, that is 400 mm) overstates it.

Step 4: Final Answer:
The nursery water requirement for 1 ha of main field, as given by Kung (1971), is 200 mm.
\[ \boxed{200 \text{ mm}} \]