Subtopic: Measurement of infiltration, soil moisture and irrigation water infiltration
Question Statement:
A field crop is irrigated when available soil water is depleted to 60%. Field capacity=32%, wilting point=12% (by weight); bulk density=1.5 g/cm³; field application efficiency=75%; root zone depth=50 cm. Find the gross depth of irrigation to bring soil moisture to field capacity (cm).
Options:
(A) 6
(B) 8
(C) 9
(D) 12
Official Answer Key:
D
Step-by-Step Solution & Explanation
Total available water (depth) = (FC−WP)/100 × BD × root depth = 0.20×1.5×50 = 15 cm. Management-allowed depletion = 60% ⇒ Net irrigation depth = 0.60×15 = 9 cm. Gross depth = Net/efficiency = 9/0.75 = 12 cm.
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