Multiple choice

Direction: The moisture holding capacity of the soil in a 100 hectare farm is 18 cm/m. The field is to be irrigated when 50 percent of the available moisture in the root zone is depleted. The irrigation water is to be supplied by a pump working for 10 hours a day, and water application efficiency is 75%. Details of crops planned for cultivation are as follows:

   
Crop Root zone depth (m) Peak rate of moisture use
(mm/day)
X 1.0 5.0
Y 0.8 4.0

The area of crop Y that can be irrigated when the available capacity of irrigation system is 40 litres/sec is

  1. 40 hectares

  2. 36 hectares

  3. 30 hectares

  4. 27 hectares
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Available moisture = 18 cm/m * 0.5 (depletion) = 9 cm/m. For crop Y (0.8m depth), depth of water = 0.8 * 9 = 7.2 cm = 72 mm. Peak rate = 4 mm/day. Irrigation interval = 72/4 = 18 days. Daily water requirement = 4 mm/day * Area. Total water needed per day = (4 * Area) / 0.75 (efficiency). Flow rate = 40 L/s = 0.04 m^3/s. Daily capacity = 0.04 * 10 * 3600 = 1440 m^3. Area = (1440 * 0.75) / (0.004 * 18 * 10000) = 27 hectares.

Keep practicing — related questions