Page 36 - soil-plant-water relationship and water requirement

SOIL-PLANT-WATER RELATIONSHIP AND WATER REQUIREMENT

Table 3.2-1: Typical Soil Water Equilibrium Points
Field Permanent Available Readily
Capacity Wilting Point Water (AW) Available
(FC) (PWP) Water = 0.5
(By Weight) (By Weight) AW
Clay 45 30 15 7.5
Clay Loam 40 25 15 7.5
Fine Sand 15 8 7 3.5

Sand 8 4 4 2.0

Figure 3.2-4 : FC and PWP Curve for Difference Soil Types

EXAMPLE 3 - 1

Field capacity: 20%
Wilting point: 13%
Root system depth: 20cm
Calculate the Total Available Water (TAW):

Solution:

% Available water = 20-13=7%
3
TAW= 0.07 x 1000 mm/m x 0.2m = 14mm (140 m /ha).

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