Subtopic: Measurement of infiltration, soil moisture and irrigation water infiltration
Question Statement:
In a cropped field: moisture content at field capacity (weight basis) = 36%; current moisture content (weight basis) = 24%; bulk density of soil = 1.5 Mg m⁻³; effective root zone depth = 0.8 m; conveyance efficiency = 80%; application efficiency = 90%. To bring soil moisture content to field capacity, the depth of irrigation in mm will be ______
Official Answer Key:
200.0 to 200.0
Step-by-Step Solution & Explanation
Net (field) depth of water required: d_net = (θ_fc − θ_current)×BD×Depth_rootzone = (0.36−0.24)×1.5×0.8 m = 0.12×1.5×0.8 = 0.144 m = 144 mm. This is the field (application) depth; to find the depth of irrigation that must be delivered (accounting for application losses), divide by application efficiency: d_field-delivery = 144/0.90 = 160 mm. To further account for conveyance losses from source to field, divide by conveyance efficiency: d_gross(at source) = 160/0.80 = 200.0 mm, matching the accepted band exactly.
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