Question

What is the moisture depth available for evapotranspiration in root of 1 m depth soil, if dry weight of soil is 1.5 gm/cc, field capacity is 30% and permanent wilting point is 10%?
1. 450 mm
2. 300 mm
3. 200 mm
4. 150 mm

Answer 1

Correct Answer - Option 2 : 300 mm

Concept: 

The depth of water stored (dw) in the root zone is given by.

 \({d_w} = \frac{{{\gamma _d}}}{{{\gamma _w}}} \times d\left( {FC - PWP} \right)\)

where,

γd = dry unit weight of soil

γw = unit weight of water

d = depth of the root zone

PWP = Permanent wilting point

 FC - Field capacity

Calculation:

Given

 FC = 30 %, PWP = 10%

γd = 1.5 g/cc, γw = 1 g/cc

d = 1 m

The depth of water stored (dw) in the root zone

\(\therefore {d_w} = \frac{{1.5}}{{1}} \times 1 \times \left( {0.30 - 0.10} \right)\)

dw = 0.3 m = 300 mm