ALTERNATE PARTIAL ROOT-ZONE SURFACE DRIP IRRIGATION FOR TOMATO: HYDRUS-2D - Management, Performance, and Applications of Micro Irrigation Systems - page 125

FIGURE 4 Temporal variation in water content at an observation point and 10 cm laterally
from the trunk of a plant.

9.3.2 ROOT WATER UPTAKE

9.3.2.1 EFFECTS OF INTERPLANT EMITTER DISTANCE ON ROOT WATER

UPTAKE
Figure 5a shows the temporal variation in water extracted by plant roots during the
simulation period for simulation scenarios 1, 4, and 7. The Fig. 5a shows that root
water uptake rate was higher in case of short IPED compared to the case of long IPED.
This is due to the large soil moisture content near the zone of maximum root density
for short IPED compared to other cases. And for simulation scenario 7, although the
wetting bulb was away from the zone of maximum root density the rate of water ex-
tracted by plant root was high at the beginning of simulation period (first 5 days). This
is attributed to the high value of antecedent water content (0.199 m3.m -3 ) that provided
more available water at the beginning of simulation period. Thus the antecedent water
content value and root distribution play a major role in controlling root water uptake
rates. Short IPED is preferable especially for root system with limited lateral exten-
sion.

9.3.2.2 EFFECTS OF IRRIGATION WATER SALINITY ON ROOT WATER

UPTAKE
The root water uptake rate depends mainly on the soil moisture content in the root
zone and the plant salt tolerance. Figure 5b shows the temporal variation in water
uptake by plant roots during the simulation period for simulation scenarios 1, 2,
and 3. The figure shows that the salinity of irrigation water has an obvious effect on
root water uptake rate. As the salinity of irrigation water increased root water uptake
rates decreased. For irrigation water salinity of 1 dS/m and 20 cm IPED, the rate of
root water uptake decreased from 0.71 to 0.51 cm/day by the end of the simula-
tion period. However, for irrigation water salinity of 2 dS/m, the rate of root water
uptake decreased from 0.71 to 0.44 cm/day compared with 0.57 cm/day for the
case of nonsaline irrigation water. On the other hand, for irrigation water salin-
ity of 2 dS/m, the root water uptake rate reached 0.40 and 0.37 cm/day by the end of