A crop has effective root zone depth of 1200 mm and monthly (30 days) crop evapotranspiration of 260 mm. The effective rainfall during 30 days period is 20 mm. The field capacity and permissible soil moisture depletion (volume basis) are 16% and 8%, respectively. The irrigation interval in days for the crop will be
Options:
(A) 30
(B) 18
(C) 12
(D) 8
Official Answer Key:
C
Step-by-Step Solution & Explanation
Net depth of water available for depletion between irrigations = (permissible depletion fraction) × (root zone depth) = 0.08 × 1200 = 96 mm.
Net daily consumptive-use demand to be met by irrigation (after crediting effective rainfall) = (ET − effective rainfall)/days = (260−20)/30 = 240/30 = 8 mm/day.
Irrigation interval = depletable depth / daily net demand = 96/8 = 12 days. Answer: (C).
Irrigation Water Conveyance and Application Methods
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