Question

The field capacity of a soil is 25%, its permanent wilting point is 15% and specific dry unit weight is 1.5. If the depth of root zone of crop is 80 cm, the storage capacity of the soil is

• A. 8 cm
• B. 10 cm
• C. 12 cm
• D. 14 cm

Answer 1

The correct option is C 12 cm

$\text{Field capacity,}FC=25$
$\text{Permanent wilting point, PWP}=15$
$\text{Specific dry unit weight,}{G}_m=1.5$
$\text{Depth of root zone}=d=80\text{cm}$
$\text{Find depth of water,}{d}_w=?$
$d_w=d\times G_m(FC-PWP)(\because G_m=\frac{{\gamma }_d}{{\gamma }_w})$
$=80\times 1.5\times (0.25-0.15)$
$d_w=12\text{cm}$
$\text{water storage capacity of the soil}=12\text{cm}$