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3. RESULTS AND DISCUSSION
3.1. Water application
During the four experimentation years, all treatments received annual equal volumes of irrigation water amounting to approximately 736 mm Table. 1. Water application
commenced towards the early April and continued up to November. Irrigation interval was fixed for 10 days due to the water allocation system and just irrigation time increased by
crop development stage. During the peak period of consumption July to August, the irrigation time increased to about 26 hrs for I1 in order to maintain adequate soil moisture
in the effective crop root zone. Irrigation scheduling was based on Class `A Pan Evaporation measurements, multiplied by the locally developed crop coefficients for
pistachio plantations.
Table 1. Daily crop water requirement and irrigation time for irrigation treatments
during irrigation season
Month Days
ET
C
mmday Daily irrigation
requirement Lday
Irrigation time hr for 10 days interval
I1 I2
I3 April
1-10 1.76
16.5 10.3
7.7 5.2
11-20 2
18.4 11.5
8.6 5.8
May 21-29
2.19 20.2
12.6 9.45
6.3 1-11
2.38 21.9
13.7 10.27
6.85 12-21
2.69 24.8
15.5 11.6
7.75 June
22-31 3.11
28.6 17.88
13.41 8.94
1-10 3.59
33.1 20.68
15.51 10.34
11-20 4.08
37.6 23.5
17.6 11.75
July 21-30
4.3 39.6
24.75 18.6
11.45 1-10
4.48 41.3
25.8 19.35
12.9 11-20
4.56 42
26.25 19.7
13.1 August
20-31 4.42
40.7 25.43
19.1 12.7
1-10 4.28
39.4 24.63
18.5 12.3
11-20 4.14
38.1 23.8
17.85 11.9
September 21-31
3.88 35.8
22.38 16.8
11.2 1-10
3.62 33.4
20.88 15.66
10.44 11-20
3.33 30.7
19.18 14.4
9.6 October
21-30 2.93
27 16.9
12.7 8.45
1-10 2.5
23 14.38
10.8 7.2
11-20 2.11
19.4 12.13
9.1 6.1
November 21-31
1.77 16.3
10.2 7.65
5.1 1-10
1.46 13.5
8.43 6.3
3.2 11-20
1.17 10.8
6.75 5.1
3.4 21-30
1.17 10.8
6.75 5.1
3.4
414.3 310.85
206.32
3.2. Moisture distribution in the soil
Spatial soil-moisture distribution in the soil was monitored by sampling, approximately 10 h after terminating the irrigation shift. The amount of water applied prior to monitoring
varied, according to season, between 11.7 to 45.6 mm10days.
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3.3. Salinity distribution in the soil
Salinity distribution in the soil as expressed by the ECe also exhibits trends similar to that of the soil moisture. For the emitters located 50 cm deep the salinity trend is presented in
Fig. 2. Accordingly, high soil salinity 8.1±11-19 dSm was recorded for different irrigation management. Less applied caused increase in ECe which attributed to less salinity
leaching out. On the other hand, soil water absorption by crop and soil surface evaporation increased salinity concentration in root zone area.
According to the Fig. 2, moisture profile for each case examined, it can be concluded that SDI maintains continuous soil leaching not only downwards, but also upwards and
radially. Primarily for emitters located at a depth of 50 cm, the soil salinity ECe in the main active root zone was in correlation with the salinity of the applied water. Extra
leaching is thus required to shift the salt front into deeper soil layers.
Figure 2. Salinity distributions, ECe, in the soil in a pistachio orchard under
saline-water subsurface drip irrigation as a function of emitter depth 50 cm below the soil surface
3.4. Yield
According to the field results, highest pistachio yields obtained when 100 of crop water requirement were applied but differences between the treatments was not significant Fig
3. Accordingly, the yield of treatments when the emitters located at a depth of 50 and 70 cm below the soil surface was almost similar 1.6 tonha. This indicated that may trees
received the required water from deeper soil layer where winter water was stored. An extended experimental and monitoring period is required in order to define trees
transpiration water compared to the irrigation water and leaching amount. The yield was not much higher than average yield in the region but the irrigation water was much less.
However, the yield has increased by year when the tree may adapted by SDI. The yield increased in last year for experiment to 7978 tonha which was almost 5 time of average
yield in the site.
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Figure. 3. Pistachio yield under different irrigaiton treatment I1, I2, and I3 and
location of emitter under the soil surface D1 and D2
3.5. Pistachio water productivity
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