Irrigation Water Conveyance and Application Methods
Subtopic: Irrigation scheduling
Question Statement:
A check basin of size 15 m × 12 m is to be irrigated using a stream of 26 litre per second. The depth of crop root zone is 1.3 m and the apparent specific gravity of the root zone soil is 1.6. The water holding capacity of the soil is 16 %. Irrigation is to be applied when the soil moisture content in the crop root zone attains 12%. Deep percolation loss is neglected. The net irrigation requirement in mm is
Options:
(A) 43.2
(B) 63.2
(C) 73.2
(D) 83.2
Official Answer Key:
D
Step-by-Step Solution & Explanation
Net depth of irrigation (to bring soil moisture from current 12% up to field capacity/water-holding-capacity of 16%, on a weight basis): d_net = (WHC − θi) × root-zone depth × apparent specific gravity = (0.16−0.12) × 1.3 m × 1.6 = 0.04 × 1.3 × 1.6 = 0.0832 m = 83.2 mm, matching option (D).
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