Page 63 - soil-plant-water relationship and water requirement

SOIL-PLANT-WATER RELATIONSHIP AND WATER REQUIREMENT

EXERCISE 6

1. A vegetable farm is developed with micro-irrigation system. If the depth of root
zone is 60 cm, the moisture at field capacity is 20 %, wilting point remain at 10 % and
ET 6 mm/day. Calculate irrigation frequency with an assumption that the irrigation
start when available moisture loss 60 %.

2. Based on the information below, determine the ;

i. amount of available moisture in the root zone.
ii. net application depth (theory) for each irrigation.

iii. gross application depth (actual) for each irrigation, if irrigation effeciency
is 75% (i.e 25% of the water quantity added loss in form of run-off,
evaporation, percolation and seepage)

iv. irrigation frequency needed.

Crop:
Root zone depth : 1.5 m
Max. evapotranspiration rate , ET : 15 mm/day

Soil:
Field capacity : 25 cm/m
Permenent wilting point : 9 cm/m

Irrigation system design :

Permissible moisture depletion : 50% from available moisture

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