If the field capacity of a soil is $35 %$ , permanent wilting point is $15 %$ , density of soil is $1.6 g / c m^{2}$ , effective depth of root zone is $75 c m$ and daily consumptive use of water for given crop is $14 m m$ , then the watering frequency to ensure efficient irrigation to the given crop will be ____ days. [Readily available moisture is same as available moisture]
17

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Solution

The correct option is A 17
Given,
$FC = 35 % = 0.35$

$PWP = 15 % = 0.15$

$Depth of root zone, d = 75 c m$

$Density of soil = 1.6 g / c c$

$Density of water = 1.0 g / c c$

$Depth of irrigation required,$
$d_{w} = \frac{γ_{d}}{γ_{w}} \times d \times [FC - PWP] = \frac{1.6}{1} \times 75 [0.35 - 0.15]$

$= 24 c m$

$Daily consumptive use = 14 m m = 1.4 c m$

$∴ Frequency of irrigation = \frac{24}{1.4} = 17.14 \approx 17 d a y s$

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