ol. IV, No. 5, November-December, 2013

Saucedo

,

5 000

4 500

4 000

3 500

3 000

2 500

2 000

1 500

1 000

500

0

Distance (cm)

Time (s)

0 2 000 4 000 6 000 8 000 10 000 12 000

Figure 1. Calibration of the Model;

ψ

d

= -15 cm and

= 1.86 cm/h,

= 0.9984.

(CUC):

=

1 1

(

)

=

1

, where

is the

infiltration lamina at point

[

] and

is the

number of points used for the calculation.

Figure 3 shows the relationship between the

optimal flow and the border length for which it

is calculated. This flow is described sufficiently

well by a linear correspondence. The figure

was generated for an irrigation lamina of 10

cm, but the behavior is similar regardless of the

irrigation lamina to be applied. The result is

similar to that obtained for the case in which no

water table is present in the soil profile, which

indicates that the mainly linear correspondence

between border length and optimal irrigation

flow is independent of the initial distribution of

the pressures in the soil. As an example, Figure

4 shows the final distribution of the infiltration

lamina for an irrigation lamina of 10 cm and a

water table depth of 100 cm for La Chontalpa

clay soil. This depth has been used to define

the initial distribution of pressures in the soil

according to equation (11).

Table 1 shows the unit flow values, that is,

the flow to be applied per unit border width

and per unit border length, corresponding to

different irrigation laminas and initial water

table depths. The empty boxes indicate that the

desired amount of water to be applied is greater

than the amount of water that can infiltrate

into the soil. Table 2 shows the irrigation

times corresponding to the unit flows shown

in Table 1. With initial positions of the water

table of 100, 150, 200 and 10 000 cm, the optimal

flow increases as the depth of the water table

increases. Since the depths considered are not

in the asymptotic zone of the moisture retention

curve, which extends from the water table to

the soil surface as a result of the distribution of

the hydrostatic pressures adopted, the expected

asymptotic behavior of the optimal irrigation

flow cannot be attained. Nevertheless, the

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