ALTERNATE PARTIAL ROOT-ZONE SURFACE DRIP IRRIGATION FOR TOMATO: HYDRUS-2D - Management, Performance, and Applications of Micro Irrigation Systems - page 128

Figure 7 shows the salinity distribution by the end of the simulation period along
a vertical section across the plane of symmetry of fl ow domain for all simulation sce-
narios. It was noted that for 20 cm IPED, soil salinity reached its highest levels in the
region located between the 40 and 65 cm depths. This is attributed to the relatively
high initial soil salinity (2 dS/m) and the limited vertical extension of the wetting bulb.
On the other hand, for 30 and 40 cm IPED, soil salinity reached its highest values at
the top soil layer. Although long IPED shows higher salinity levels at the soil surface,
soil salinity was approximately the same in the region between the 40 and 65 cm
depths for both short and long IPED. Using long IPED with brackish irrigation water
in APRDI is not suitable for plants with shallow root system. However, short IPED
is more suitable for plants with shallow root system even when using brackish irriga-
tion water as compared to plants with deep root system taking into consideration crop
salinity tolerance.

9.3.4 WATER BALANCE
Water balance for all simulation scenarios is shown in Table 3. Water balance was
expressed in percent of total applied water during the simulation period. Soil evapora-
tion was approximately the same in all simulation scenarios. In addition, plant roots
extracted more than 85% of the applied irrigation water. Consequently, most of the
applied irrigation water was effectively used through the root system. Maximum root
water uptake occurred in simulation scenario 1.

TABLE 3 Water balance components in different simulation scenarios in percent of total
applied water.

Scenario num-
ber

Root water
uptake

Drainage Soil evapora-

tion

Root zone stor-
age

1 113.12 7.44 6.08 - 26.64

2 106.46 7.56 6.09 - 20.11

3 96.65 8.17 6.09 - 10.90

4 106.03 8.65 6.03 - 20.71

5 99.32 8.90 6.09 - 14.30

6 90.87 9.64 6.07 - 6.58

7 97.20 11.94 5.54 - 14.68

8 91.93 12.26 5.88 - 10.07

9 85.04 13.09 5.96 - 4.10

IPED played a major role in controlling root water uptake. Although the applied
water was less than crop ET pot , deep percolation below the root zone occurred. Maxi-
mum drainage took place in simulation scenario 9. This is due to the higher salin-