Irrigation Water Conveyance and Application Methods
Subtopic: Irrigation scheduling
Question Statement:
A sandy loam soil has a water holding capacity of 140 mm m⁻¹ depth between field capacity and wilting point. The area to be irrigated is 60 ha and the depth of effective root zone is 0.30 m. The management allowed soil moisture depletion is 40% and the consumptive use is 6 mm per day. The conveyance and application efficiencies are estimated to be 80 and 50 percent respectively. There are no leaching requirements as well as no rainfall and groundwater contributions to the crop water requirement. The frequency of irrigation will be
Options:
(A) 1 day
(B) 3 days
(C) 7 days
(D) 5 days
Official Answer Key:
B
Step-by-Step Solution & Explanation
Net irrigation requirement per event = AWC × root depth × MAD = 140 mm/m × 0.30 m × 0.40 = 16.8 mm. Irrigation frequency = NIR/consumptive use = 16.8/6 = 2.8 days, rounded down to the nearest whole day for a practical/conservative schedule = 3 days (irrigating any less frequently would exceed the allowable depletion).
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