257 T. Oweis et al. European Journal of Agronomy 11 1999 255–266
average rainfall gradient of about 200–600 mm then, little effective rainfall occurred until 37 mm
rainfall in May made a substantial contribution to year
−1. Wide inter-annual and inter-season rainfall variation is characteristic of the region. In such
crop yield. The rainfall in the second season was slightly above average, but was poorly distributed,
conditions, SI can have a large impact on yield in normal and dry years, but little or no irrigation is
with most of the rainfall in January–February and little thereafter; a heat wave occurred in April and
required in favorable years. Our objective was to identify, in a 4 year field trial 1992–1996, at
May. The rainfall in the third year was about average, and was well distributed. The fourth year
ICARDA’s main station, Tel Hadya, near Aleppo in northern Syria mean annual rainfall, 330 mm,
was above average and well distributed, but had higher temperatures during the grain-filling period.
the most effective combinations of SI, N fertilizer, and sowing dates for enhanced yield and quality
of four improved durum wheat varieties. 2.2. Trial treatments and design
The treatments included: 1. three sowing dates, which varied depending on
2. Materials and methods
the year early, mid-November; normal, mid- December; and late, mid-January;
2.1. Soil and weather 2. four SI rates; rain-fed no irrigation, full SI
irrigation to avoid moisture stress, and 13, The soil at Tel Hadya station Ryan et al.,
1997a is generally deep over 1 m and has a and 23 of full SI.
3. Four N application rates 0, 50, 100, and heavy clay texture fine clay, montmorillonitic,
thermic Calcixerollic Xerochrept. The relevant 150 kg N ha
−1; and 4. Four high-yielding, widely adapted durum
properties are
as follows:
pH 8.0; CaCO
3 ,
240 g kg −1; organic matter, 8.4 g kg−1; cation
wheat varieties: Cham 1: resistant to yellow rust;
exchange capacity, 52 cmol kg −1 at the beginning
of the trial, extractable potassium by 1 N ammo- Lahn: irrigated areas, cold tolerant;
Cham 3: drought and heat tolerant, high grain nium acetate, pH 7.0 546 mg kg
−1 well above the critical level, and low extractable phosphorus
quality for semolina products; Omrabi 5: high drought tolerance, diverse
values 0.5 M NaHCO 3
, 5 mg kg−1 and mineral
N NO 3M
N +NH
4M N to a depth of 60 cm
environments. A split-split-split plot design, with three repli-
10 mg kg−1. This clay soil has good structure and is well drained, with an infiltration rate of
cates, was used. Sowing dates were represented by the main plots, varieties by the sub-plots, water
11 mm h −1. The mean soil moisture in the top
100 cm soil at the field capacity −33 kPa and at
rates by the sub-sub plots, and the N rates by sub- sub-sub plots 2.25
×6.3 m plot size. The site the permanent wilting point
−1500 kPa is about 48 and 24
by volume, respectively. Throughout alternated each year between two adjacent blocks
following the
cereallegume or
safflower the growing season, the profile undergoes recharge
from November to March and discharge from Carthamus tinctorius rotation system practised at
Tel Hadya. Thus, in years 1 and 2, the trial then until June Harris, 1995. Only in above-
normal rainfall years is the profile wetted below followed
chickpea Cicer
arietinum L.
and safflower in years 3 and 4.
1.5 m. Rainfall was variable during the four growing
A trickle-irrigation system was designed and installed to provide a uniform soil moisture pattern
seasons in total amount, i.e. 281 mm 19921993, 358 mm 19931994, 330 mm 19941995 and
within each SI treatment. Pressure-compensating emitters, with an approximate discharge rate of
395 mm 19951996 and in distribution Table 1. The first season showed below-average rainfall i.e.
2 l h −1, were installed along polyethylene lines of
20 mm diameter. The spacing between laterals was 330 mm. Following the first rain on 15 November,
subsequent rain was well distributed until March; 70 cm and between emitters 17.5, 35.0, and
258 T. Oweis et al. European Journal of Agronomy 11 1999 255–266
Table 1 Mean monthly values of maximum and minimum temperature, Class A evaporation, and rainfall at Tel Hadya in northern Syria,
1992–1996 a
Month T
max °C
T min
°C E
p mm
Rainfall mm T
max °C
T min
°C E
P mm
Rainfall mm 19921993
19931994 October
30.7 11.5
208 30.7
12.8 214
18 November
17.8 5.6
95 50
16.1 4.1
71 42
December 9.0
2.2 27
47 14.1
4.9 40
16 January
11.5 −0.3
48 51
13.3 3.7
37 109
February 11.8
0.1 61
45 13.8
2.8 64
137 March
16.8 2.4
105 40
18.9 4.0
101 12
April 24.0
7.3 182
2 26.9
8.3 197
11 May
27.0 11.4
218 45
31.6 11.8
298 13
June 34.4
15.3 377
1 34.7
17.7 432
∑ 1320
281 1453
358 19941995
19951996 October
30.3 14.8
187 12
28.3 10.5
193 9
November 17.8
7.5 75
109 17.2
4.6 66
59 December
9.6 1.6
38 45
12.4 2.0
36 31
January 12.2
3.7 35
41 11.2
3.3 39
74 February
16.5 2.7
56 18
14.4 4.3
59 47
March 18.9
3.4 98
33 15.8
6.6 66
143 April
23.1 6.9
158 44
20.6 6.7
117 27
May 31.6
11.5 275
27 32.2
12.3 278
5 June
35.7 18.6
406 1
35.6 17.6
385 ∑
1328 330
1239 395
a Tmax=maximum temperature; Tmin=minimum temperature; Ep=Class-A pan evapotranspiration.
52.5 cm, corresponding to the irrigated treatments was planted in 17.5 cm rows at a rate of approxi-
mately 300 seeds m −2, with N applied half at
full SI, 23 and 13 SI, respectively. The system of irrigation used in this study would not be economi-
sowing and half top-dressed at the early tillering stage. As P was not a variable, a blanket applica-
cal for wheat at the farmer’s land, but because of difficulties in obtaining good data with sprinklers
tion of 30 kg P ha −1 was applied to all plots prior
to sowing. the area is windy, this system was used as a
research tool to apply water accurately and evenly. Soil moisture was measured weekly, before and
after each water application, and after each rain, Various emitter and lateral spacing together with
a range of irrigation scheduling options were exam- using neutron probes. Access tubes were inserted
in each of the sub-sub-sub plots of one replicate ined prior to this experiment to select the design
parameters that achieve a uniform distribution of up to 1.8 m depth depending on soil depth for
one variety Omrabi 5. Water was applied to all water similar to that of a sprinkler system
Oweis, 1992. treatments of the same date of sowing at the same
time, i.e. when the root zone of the full SI treatment The source of the irrigation water was good-
quality groundwater EC 0.62 dS m −1, SAR, 1.1.
with 100 kg N ha −1 had lost 50
of its available moisture 12 the difference between field capacity
The cation concentrations were Ca ++, 3.4;
Mg ++, 1.7; Na+, 1.7; and K+, 0.06 meq l−1. The
and wilting point. The amount of water, which was then given, was calculated to restore root-
corresponding anions were: CO −−
3 , trace; HCO
− 3
, 2.6; SO
−− 4
, 1.7; and NO −
3 , 1.32 meq l
−1. The crop zone moisture to near field capacity. The other
259 T. Oweis et al. European Journal of Agronomy 11 1999 255–266
Table 2 Amount of irrigation water, application dates, and emergence dates for durum wheat sown at different times in the full supplemental
irrigation SI treatment Season
Sowing date a
Emergence date Irrigation amount mm
b and date Total
19921993 10 November 1992
9 December 1992 133 24; 146 154; 118 234;151 215
548 10 December 1992
16 January 1993 95 14; 100 234; 100 45; 146 215
441 16 January 1993
20 February 1993 62 64; 84 234; 130 225
276 19931994
5 November 1993 22 November 1993
113 64; 85 214; 125 165 323
5 December 1993 20 December 1993
106 74; 84 214; 164 155 354
12 January 1994 28 January 1994
80 54; 89 224; 150 165 319
19941995 8 November 1994
23 November 1994 50 93; 65 273; 145 144; 94 65
354 10 December 1994
30 December 1994 63 273; 97 154; 94 65
254 15 January 1995
6 February 1995 42 293; 122 154; 104 55
268 19951996
5 November 1995 17 November 1995
100 55; 80 145 180
12 December 1995 3 January 1996
100 65; 100 145 200
28 January 1996 17 February 1996
100 75; 120 145; 100 265 320
a The dates represent early, normal, and late sowing times. b Gross amount of SI water mm applied to the full SI treatment; the other irrigation rates were 23 and 13 of the amount applied
to full SI application dates in parentheses.
treatments automatically received fixed propor-
3. Results
