Agriculture Reference
In-Depth Information
ity values in the zone of maximum root density that reduced the amount of water
extracted by plant roots. In contrast, minimum drainage occurred during the 20 cm
IPED scenarios. Using brackish irrigation water had insignifi cant effect on drainage in
case of short IPED. Therefore, short IPED with or without brackish irrigation water is
preferable to reduce groundwater contamination risk. It is worth noting that the root
zone storage values were negative in all simulation scenarios and the root water uptake
in some simulation scenarios exceeded the amount of applied irrigation water. This
is attributed to the defi cit in applied irrigation water and thus the crop is under stress
throughout the simulation period. Thereby, the defi cit in applied irrigation water was
compensated by soil water contribution. Thus, antecedent water content value has a
signifi cant effect on the water balance components.
9.4 CONCLUSIONS
Understanding of soil moisture dynamics and salinity distribution is essential when
selecting appropriate irrigation method that help saving water without crop yield re-
duction. In this study, HYDRUS-2D was used to simulate water and salinity move-
ment under APRDI for growing tomato with two varying factors namely, IPED and
irrigation water salinity. Simulations were conducted for loamy sand during a 40-day
period considering three IPED (20, 30, and 40 cm) and three irrigation water salinity
levels (0, 1, and 2 dS/m). The applied irrigation water was assumed 25% less than
conventional surface drip irrigation system.
Simulation results revealed that due to the limited extension of wetting bulb, wa-
ter content in the zone of maximum root density by the end of simulation period was
higher in case of short IPED (20 cm) than in long IPED (30 and 40 cm). Thereby,
root water uptake rate was higher in case of short IPED. Therefore, it is preferable to
regulate the IPED according to soil hydraulic properties and plant root system. IPED
shows a great impact on surface soil salinity at plant location when using APRI with
nonsaline irrigation water in initially saline soil. Only 20 cm IPED did not show any
response to the relatively high initial soil salinity value (2 dS/m). Surface soil salinity
was lower than the initial values. Therefore, APRDI with short IPED is recommended
when using nonsaline irrigation water in initially saline soil to reduce the salinity ef-
fects on seed germination. The effect of irrigation water salinity on root water uptake
increased as the IPED increased. As irrigation water salinity increased the root water
uptake decreased. Simulation results also showed that the effect of using brackish ir-
rigation water on soil salinity values was less distinct in case of 20 cm compared to 30
and 40 cm IPED, respectively. Nevertheless, soil salinity levels at the middle of the
fl ow domain in case of 20 cm IPED with irrigation water salinity = 2 dS/m was ap-
proximately the same as in case of 30 cm IPED with non saline irrigation water. Thus,
IPED has a great impact on salinity values at soil surface and plays a major role in
controlling root water uptake.
Soil salinity reached its highest values at the top soil layer followed by the soil
layer between the 40 and 65 cm depths in case of long IPED (30 and 40 cm). However,
highest soil salinity values were between depths 40 and 65 cm in case of 20 cm IPED.
Therefore, using long IPED with brackish irrigation water in APRDI is not suitable
Search WWH ::
Custom Search