Agriculture Reference
In-Depth Information
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. The
irrigation period was calculated according to emitter discharge of 1.0 L per hour and
crop water requirements. Table 2 shows the different scenarios used in this chapter.
TABLE 2
Simulation scenarios for a sandy loam soil.
Scenario num-
ber
Inter-plant emitter
distance
cm
Salinity of ir-
rigation water
dS/m
Irrigation
interval (days)
Irrigation
period
(days)
1
20
0
40
0.115
2
20
1
40
0.115
3
20
2
40
0.115
4
30
0
40
0.115
5
30
1
40
0.115
6
30
2
40
0.115
7
40
0
40
0.115
8
40
1
40
0.115
9
40
2
40
0.115
9.3 RESULTS AND DISCUSSION
9.3.1 WETTING PATTERNS
9.3.1.1 EFFECT OF INTERPLANT EMITTER SPACING ON WATER CONTENT
DISTRIBUTION
For all simulation scenarios, at the beginning of each irrigation event, the soil mois-
ture content increased in the region close to the emitter, after that, the wetting front
extended laterally and in depth. Figure 3 shows the evolution of the wetting front at
three elapsed time periods (after the first two irrigation events and after last irrigation
event) for simulation scenarios 1, 4, and 7. It was noted that the size of the wetted
zone around the emitter was approximately the same in all simulation scenarios. Due
to gravity, the vertical spread of the water was larger than the lateral. Wetted radius at
soil surface was about 20 cm while wetted depth was about 25 cm directly below the
emitter. Therefore, for different IPED, approximately half of plant root system was
always exposed to drying cycle.
For all simulation scenarios, just before the next irrigation event, substantial reduc-
tion in moisture content occurred around the emitter because of the water uptake by
the plant roots. Similar wetting and drying cycles occurred during the entire simula-
tion period. Figure 3 also manifests that after the end of last irrigation event, the water
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