Question

After how many days will you supply water to soil in order to insure sufficient irrigation of the given crop if - i) Field capacity of soil = 28% ii) Permanent melting point = 13% iii) Density of soil = 1.3 gm/cc iv) Effective depth of root zone = 70 cm v) Daily consumptive use of water for given crop = 12 mm vi) Assume readily available moisture = 80% of available moisture

Answer 1

Answer:

Available moisture = Field capacity - permanent wilting point

= 27-14=13%

Let the readily available moisture be 80% of the available moisture

Readily available moisture= 13 x 0.8 = 10.4%

Maximum level upto which soil moisture may be allowed to be depleted (mo) = 27- 10.4

= 16.6%

Depth of water stored in root zone during each watering = (Density of soil x depth of root zone) x (Field capacity - mo ) / (density of water)

= (15 x 0.75) x (0.27 - 0.166) / (9.81)

= 0.119 m

Daily consumptive use of water = 1.1 cm

Watering frequency = 11.9 / 1.1 = 10.82 days = 11 days (approx)