Vol.2, No.3, 273-282 (2011)
Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/AS/
Agricultural Scienc es
Water use efficiency and yield of winter wheat under
different irrigation regimes in a semi-arid region
Mohamed Hakim Kharrou1*, Salah Er-Raki2, Ahmed Chehbouni3, Benoit Duchemin4,
Vincent Simonneaux4, Michel LePage4, Lahcen Ouzine1, Lionel Jarlan4,5
1ORMVAH, Office Régional de Mise en Valeur Agricole du Haouz, Marrakech, Morocco; *Corresponding Author:
2LP2M2E, Department of Physics, Faculty of Sciences and Technology, Marrakech, Morocco;
3FSSM, Faculté des Sciences Semlalia Marrakech, Morocco;
4CESBIO, Centre des Etudes Spatiales de la BIOsphère, Toulouse, France;
5Direction de la Météorologie Nationale, Casablanca, Maroc.
Received 27 May 2011; revised 19 July 2011; accepted 31 July 2011.
In irrigation schemes under rotational water
supply in semi-arid region, the water allocation
and irrigation scheduling are often based on a
fixed-area proportionate water depth with every
irrigation cycle irrespective of crops and their
growth st ages, for an equitable water supply. An
experiment was conducted during the 2004-
2005 seas on in Haouz irrigated area in Morocc o,
which objective w as 1) to evaluate the effects of
the surface irrigation scheduling method (ex-
isting rule) adopted by the irrigation agency on
winter wheat production compared to a full ir-
rigation method and 2) to evaluate drip irrigation
versus surface irrigation impacts on water sav-
ing and yield of w inter wheat. The methodology
was based on the FAO-56 dual approach for the
surface irrigation scheduling. Ground measure-
ments of the Normalized Difference Vegetation
Index (NDVI) were used to derive the basal crop
coefficient and the vegetation fraction cover.
The simple FAO-56 approach was used for drip
irrigation scheduling. For surface irrigation, the
existing rule approach resulted in yield and
WUE reductions of 22% and 15%, respectively,
compared with the optimized irrigation sched-
uling proposed by the FAO-56 for full irrigation
treatment. This revealed the negative effects of
the irrigation schedules adopted in irrigation
schemes under rot ationa l water supply on crops
productivity. It was also demonstrated that drip
irrigation applied to wheat was more efficient
with 20% of water saving in comparison with
surface irrigation (full irrigation treatment). Drip
irrigation gives also higher wheat yield com-
pared to surface irrigation (+28% and +52% for
full irrigation and existing rule treatments re-
spectively). The same improvement was ob-
served for water use efficiency (+24% and +59%
Keywords: Water Use Efficency; Yield; Surface
and Drip Irrigation; FAO-56; Irrigation Sche duling;
Water demand has significantly increased over the last
decades while available water resources are becoming
increasingly scarce. This is mainly due to the combined
effect of climate change, persistent drought and the in-
crease of water demands related to increase in irrigated
surfaces, urbanization and tourism recreational projects.
In this context, improvement of water management in
agriculture, which is the biggest water consumer, is nec-
essary to enhance agricultural productivity in order to
meet food demands of the growing population.
The Moroccan agriculture sector contributes 19% of
the GNP and plays a substantial role in the macroeco-
nomic balance of the country. Cereal crops, mainly win-
ter wheat, occupy 75% of agricultural areas, and directly
contribute to the food security of the country [1]. How-
ever, the cereal productivity is still below the potential
mainly because of the traditional management of farms
and the climatic conditions characterized by poor and
irregular rainfall (a reduction in spring precipitation has
already been highlighted by [2]) which requires exten-
sive irrigation for cereal production stability. Therefore
in irrigated areas, a reasonable irrigation scheduling is a
M. H. Kharrou et al. / Agricultural Science 2 (2011) 273-282
Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/AS/
key factor to help farmers increase crop yield and save
water regarding limited water resources. The water use
efficiency (WUE) is one of the most important indices
for determining optimal water management practices; its
use has been reviewed by [3,4]. When irrigation is ap-
plied at the critical stages of plant development, values
of WUE are larger, especially under deficit irrigation [5].
Also, high irrigation water use efficiency (WUE) for
wheat could be achieved by saving irrigation rates under
drip system [6]. This result is of great importance since
the Moroccan government has promoted the use of water
saving technologies by providing financial support for
infrastructure which requires great training and exten-
sion efforts [1].
Moreover, in irrigation schemes under rotational water
supply in semiarid environment, the existing rules for
water allocation are often based on applying a fixed-area
proportionate depth of water with every irrigation cycle
irrespective of the crops and their growth stages and that
for ease of irrigation schemes operation. This frequently
is likely to result in excessive water depths being applied
when large amount of water are available or, by contrast,
water stress periods occurring when irrigation intervals
are too large. This is the case in the area of study, the
Haouz plain, one of the most important agricultural areas
in Morocco. Thus, the effects of these irrigation sched-
uling rules on crops productivity have to be assessed in
order to improve water management.
A fundamental requirement for accurate irrigation
scheduling is to determine crop water needs or crop
evapotranspiration (ETc). The most common and practi-
cal approach used for estimating crop evapotranspira-
tion is the FAO-56 method published by the Food and
Agricultural Organization (FAO) of the UN as FAO irri-
gation and Drainage paper No. 56 [7]. This approach has
been widely used due to its simplicity and its applicabil-
ity at operational basis with satisfying results under
various climates and over several crops [8-18]. In addi-
tion to the single crop coefficient (Kc) approach, FAO-
56 introduced dual crop coefficient procedure where the
single Kc is separated into a basal crop coefficient, or
Kcb (primary crop transpiration), and a soil evaporation
coefficient (Ke). The FAO-56 dual procedure provides
an excellent framework for calculating daily ETc. How-
ever, successful application is highly dependent on the
ability to derive an appropriate Kcb curve that matches
the actual crop growth and ETc conditions that occur
during a given season [7].
Multispectral vegetation indices, such as the Normal-
ized Difference Vegetation Index (NDVI), have gained
wide acceptance for estimating several crop growth pa-
rameters. Several studies have highlighted the potential
of using NDVI for crop coefficients estimation [10,12,15,
17]. In this study, we have used ground radiometric mea-
surements to derive NDVI-based Kcb and NDVI-based
fraction cover (fc) along with the FAO-56 dual proce-
dure to schedule surface irrigation and the single Kc pro-
cedure for drip irrigation scheduling.
It has been found that the impact of limited irrigation
and soil water deficit on crop yield or WUE depends on
the particular growth stage of the crop, and the most
sensitive stage can vary region-by-region due to regional
variability in environment and agronomic practices [19].
In the Mediterranean region, [20] reported that wheat
response to water stress is more sensitive from stem-
elongation to booting, followed by anthesis and grain-
filling stages. For the Loess Plateau of China, [21] found
that winter wheat sensitivity to drought occurs, in de-
creasing order of importance, during the stages of anthe-
sis, booting, stem elongation, and grain filling.
Although relationships between wheat Grain yield
(GY) and amounts of water applied or evapotranspira-
tion, reported by several authors, have been widely used
as a guideline for irrigation [4,20,22], the effects of tim-
ing applications, dictated by the irrigation schedules, on
wheat GY and WUE cannot be explained by these rela-
tionships. So, the objective of this research was to evalu-
ate the effects of the existing rules of surface irrigation
allocation and scheduling in a rotational irrigation sys-
tem on yield and water use efficiency of winter wheat in
a semi arid environment. Also, a comparison with drip
irrigation method was included in the study.
2.1. Experimental Site and Data Collection
Field experiment was conducted during 2004-2005
season at the experimental station of the irrigation
agency called Office Régional de Mise en Valeur Agri-
cole du Haouz (ORMVAH). This station which is about
6 hectares was created in 1990 and located 15 km West
of Marrakech city in an irrigation scheme (latitude
31˚3756N, longitude 8˚0924, 412 m over mean sea
level). The climate of the region is typically Mediterra-
nean semi-arid, with around 250 mm of average annual
rainfall, concentrated mainly from autumn to spring, and
an average annual reference evapotranspiration (ETo) of
about 1600 mm. The soil at the experimental site is a
silty clay loam with a bulk density of 1.4 g/cm3. Winter
wheat (“Arrehane 1774” cultivar) was sown on 8th De-
cember 2004 at a rate of 216 Kg/ha. The experimental
area consisted of two plots PG3 and PL3 of 0.60 and
0.36 ha respectively.
All the experimental plots had the same characteristics
and the same crop management practice (soil preparation,
fertilizer and pest control etc.) and they were fallowed
M. H. Kharrou et al. / Agricultural Science 2 (2011) 273-282
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since 2002. They differ only in the irrigation timing and
water amounts applied in order to limit the complexities
in the discussion of the influence of different irrigation
scheduling rules. Fertilizer was applied manually in four
split applications, with the first application at planting,
consisting of 200 kg·ha1 of ammonium sulfate (21% N),
225 kg·ha1 of triple super phosphate (45% P2O5), and
100 kg·ha1 of sulfate of potash (48% K2O). The other
applications were at 51, 100 and 121 days after planting
and included 133, 109 and 72 kg·ha1 of urea respec-
tively. Weeds were controlled with specific chemical
applications. A weather station installed in the experi-
mental station provided hourly measurements of climatic
parameters (solar radiation, wind speed, relative humid-
ity, and air temperature). Punctual measurements of soil
water content at different depths (from 0.10 m to 0.80 m)
were made using gravimetric soil water sampling. Also,
crop height (Ht) and root depth (Zr) were measured dur-
ing the growing season.
In order to assess wheat crop phenology and evaluate
the irrigation treatments effects on it, the Leaf Area In-
dex (m²/m²) was measured every two weeks using hemi-
spherical photographs, based on a method calibrated in a
previous study using LAI ground measurements [23].
Before harvesting, five 1 m2 plots were selected at ran-
dom to measure the grain yield components and yield
was measured by weighing after harvesting.
Finally, measurements of canopy reflectance were
carried out using a hand-held radiometer (MSR87 Mul-
tiSpectral Radiometer, Cropscan Inc., USA) at the same
dates of hemispherical photo shots. From the reflectance
measurements, the normalized difference vegetation
index [24] was computed. In addition, the fraction cover
of the vegetation was derived from NDVI using a rela-
tionship previously calibrated on this crop in the area
f1.18NDVI NDVI min
where NDVImin is the NDVI value for the bare soil equal
to 0.147.
2.2. Irrigation Treatments and Irrigation
Scheduling Methods
Two surface irrigation scheduling treatments were ap-
plied in the PG3 plot, with two replications each: irriga-
tion scheduling based on the FAO-56 dual procedure
(full irrigation) and irrigation scheduling according to
the existing rule adopted by the irrigation agency (exist-
ing rule approach). Another treatment (drip irrigation)
consisting of FAO-56 single approach for drip irrigation
scheduling was employed within PL3 plot.
The irrigation amounts applied were volumetrically
measured using records of water level in a tank with 200
m3 capacity in the surface irrigation case and, using a
water meter in the drip irrigation case.
For the two surface irrigation treatments, the border
system, which is the most common irrigation practice in
the region, was adopted and the water was applied to
strips of 5 m wide and 25 m length. The drip irrigation
system adopted comprises a laterals spacing of 1.0 m
which were 16 mm in diameter. The emitters were inline
type with spacing of 0.4 m and had 4.0 l/h flow rate at
1.0 atm pressure.
The irrigation is scheduled, in the case of existing rule
approach, according to the water delivery schedules pre-
pared by irrigation managers for the irrigation scheme.
Predetermined annual quota according to surface water
availability in dams is allocated for irrigation at the be-
ginning of the season. This water volume is distributed
on a fixed-area proportionate water allocation basis pro-
viding the same water depth per hectare to farmers. Then,
the dates and duration of water delivery to the fields
(using rotational irrigation) are pre-sets for every irriga-
tion cycle throughout the season in arrangement with the
Water User Associations representing the farmers of the
irrigation scheme.
In the case of full irrigation treatment, the timing and
the amounts of water to apply were planned in order to
avoid crop water stress. Thus, irrigation was scheduled
to cancel the soil water depletion and the water depth
was calculated in order to bring the soil water content to
its total available water (TAW). The irrigation timing, in
this case, is determined when the stress coefficient (Ks)
reached a threshold value considered equal to 0.6 for the
wheat according to [25].
The irrigation is scheduled, for drip irrigation treat-
ment, based on the soil water balance method in which
the drainage and runoff were neglected and the net irri-
gation depth was estimated by subtracting the rainfall
from the calculated crop evapotranspiration on daily
basis using this relationship:
 (2)
where IR, ETo, Kc and R refer respectively to net depth
of irrigation (mm·d1), reference evapotranspiration
(mm·d1), crop coefficient and rainfall (mm·d1).
2.3. FAO-56 Procedure Parameters and
Water Use Efficiency
The FAO-56 is based on the concepts of reference
evapotranspiration ETo and crop coefficients introduced
to separate the standard climatic demand (ETo) from the
plant response ETc [7]. The single method relies on the
following equation:
M. H. Kharrou et al. / Agricultural Science 2 (2011) 273-282
Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/AS/
where Kc is the single crop coefficient. The daily refer-
ence evapotranspiration, ETo, is calculated according to
the FAO Penman-Monteith method [7]. Daily values of
the climatic parameters used for calculating ETo are ob-
tained from the weather station installed in the experi-
mental station.
The dual method accounts for variations in soil water
availability, inducing either stress and soil evaporation,
and is based on the following equation:
cb e
ETcKs KKETo (4)
where Kcb is the basal crop coefficient derived from
NDVI using this previously calibrated relationship for
wheat crop in the region [23] :
cb min
K1.64NDVI NDVI  (5)
Ke and Ks are calculated based on daily water balance
computation in the surface soil evaporation layer of ef-
fective depth (Ze) and in the root zone (Zr), respectively,
according to [7].
The soil parameters that were used in the FAO-56
procedure for calculating Ke, Ks and thus crop evapo-
transpiration (ETc) are presented in Table 1.
p is the fraction of TAW that a crop can extract from
the root zone without suffering water stress. The rec-
ommended values for p, given in Table 2 of FAO-56
paper [7], apply for ETc 5 mm/day. In this study, the
value for p was adjusted for different ETc according to p
= p (the table 22 in FAO-56 paper) + 0.04x(5 – ETc) [7].
The FAO-56 dual procedure for the full irrigation
treatment was implemented using a software developed
in EXCEL [7]. Once the model parameters were updated
using data collected, and in order to predict future dates
and amounts of irrigation, daily average climatic data
(ETo, wind speed and relative humidity), and linear ex-
trapolations for crop parameters (Kcb, fc, crop height Ht
and root depth Zr) were used. Since, the water balance
approach for irrigation scheduling is based on estimates
and is not always accurate, actual readings of crop height
(Ht) and root depth (Zr) were taken during the growing
season to adjust the predictions, and also the measured
Tab le 1 . The soil parameters used for the determination of Ke,
Ks and crop evapotranspiration (ETc) following the FAO-56
Soil parameters Values
Field capacity, θFC (m3/m3)
Wilting point, θwp (m3/m3)
Maximum effective rooting depth, Zr (m)
Depth of the evaporation soil layer, Ze (m)
Total evaporable water, TEW (mm)
Readily evaporable water, REW (mm)
Total available water, TAW (mm/m)
Wetting fraction, fw (fraction)
Readily available water, RAW (mm/m)
p × TAW
soil water was used to update, if necessary, the estimated
Root zone depletion (Dr) [26].
In the case of existing rule treatment, although irriga-
tion was not driven by FAO budget, the same parameters
as for full irrigation plots were observed and computed
in order to compare the two treatments and especially
their effects on stress.
Finally, for drip irrigation treatment, the crop evapo-
transpiration was calculated using the FAO simple crop
coefficient approach with Kc values of 0.30 for Kcini,
1.15 for Kcmid and 0.4 for Kcend taken directly from the
table 12 in FAO-56 paper [7].
Water use efficiency (WUE, kg·m3) regarding yield
was finally calculated as [27]:
where ET (mm) is the evapotranspiration calculated
using the previous FAO method and GY is the measured
Grain Yield (kg·ha1).
3.1. Water Consumption
The irrigation timing and the water depths applied for
the different irrigation schedules are shown in Table 2.
The main difference between three treatments was the
annual amount of irrigation water, which was 455, 396
and 362 mm for full irrigation, existing rule and Drip
irrigation treatments, respectively. Because the season
was dry (only 52 mm amount of rainfall during the
growing cycle), the irrigation water was very important
and represented about 90% of the total water applied.
Drip irrigation scheduling was found to be more efficient
with water saving of about 20% comparatively to surface
irrigation with the full irrigation approach. The latter
consumes 10% more water than the existing rule ap-
proach to avoid crop stress. Also, it can be seen that for
Table 2. Irrigation date and water amount (mm).
water amount applied per treatment (mm)
Irrigation date Full
DEC 12/23/04 70
01/13/05 68
JAN 01/14/0565.5 65
FEB 02/16/05 64.5
MARCH 03/20/05 57.5
04/02/05 136
APRIL 04/04/05141 95
TOTAL Irrigation 455 396 362
TOTAL Rainfall 52 52 52
(Irrigation + Rainfall) 507 448 414
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surface irrigation treatments, the number of irrigation
events was same for both treatments (5 irrigations ap-
plied). The existing rule and full irrigation schedules
proposed very close amounts and irrigation dates at the
beginning of the growing period (December-January)
but results strongly differ during the core of the season.
Indeed, a strong delay of the irrigation event in February
was observed for the existing rule treatment compara-
tively to full irrigation and the water depth applied was
significantly lower in March. The consequences of these
discrepancies on the wheat development are analyzed
3.2. Crop Phenological Response to
Irrigation Method
Figure 1 displays the seasonal time courses of LAI
(Figure 1(a)) and NDVI (Figure 1(b)) for the three irri-
gation methods described above. The two variables show
comparable seasonal patterns following the dynamics of
Figure 1. Seasonal time course of LAI and NDVI of winter
wheat for the three irrigation treatments.
crop growth. It can be seen that irrigation scheduling had
a significant influence on LAI (Figure 1(a)); the ob-
served LAI was higher for drip irrigation treatment, with
maximum values being 4.8, 5.1 and 5.8 m2/m2 respec-
tively for the existing rule approach, full irrigation and
drip irrigation treatments. These globally high values of
LAI (>4) indicate acceptable growth conditions for all
treatments. However, it can be seen that the delay of 14
days in the date of irrigation on February (57th day after
sowing) for the existing rule treatment has produced a
crop growth slow-down and a LAI reduction suggesting
that the crop has experienced a water stress. It can be
inferred that with adequate water application, LAI can
be increased so that light energy is better utilized and the
crop development is improved.
The NDVI minimum value was measured at the be-
ginning of the growing cycle over the dry bare soil and
was about 0.147 in agreement with the value obtained
previously in the same region [23]. As the Leaf Area
Index, the NDVI increased from crop emergence until
maximum value was attained about 93 days after sowing
(Figure 1(b)) and then began to decrease rather sharply
through the end of the season. NDVI maximum values
were 0.88, 0.91 and 0.95 for existing rule approach, full
irrigation and drip irrigation treatments respectively. The
NDVI curves remains flat out at mid-season as the
NDVI saturates for high values of LAI as previously
reported by [23]. The NDVI values were slightly higher
for drip irrigation treatment than the two surface irriga-
tion treatments especially during the late-season since
the crop was still irrigated by drip system which delayed
the crop senescence. Also, NDVI values were slightly
higher for the full irrigation treatment than existing rule
treatment especially during the mid and late-season
which indicated that the crop has experienced a water
stress induced by a long irrigation interval in February
which coincides with stem extension stage and the insuf-
ficient water amount applied for the forth irrigation
event which coincided with the flowering stage.
3.3. Performance of FAO Dual Procedure for
Irrigation Scheduling
3.3.1. Crop Coefficients
The Kcb average values obtained at three stages (ini-
tial, mid-season and end-season) were 0.14, 1.20 and
0.29 respectively, with a maximum of 1.27 for full irri-
gation treatment, and 0.18, 1.16 and 0.25 respectively
with a maximum of 1.21 for existing rule treatment.
These values are slightly different than those given by
[7] (Kcbini = 0.15, Kcbmid = 1.10, Kcbend = 0.25) since
the Kcb derived from NDVI measurements reflects the
local conditions.
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This result illustrates the interest of remote sensing
data to derive Kcb values since it offers first the ability
to account for variations in plant growth due to specific
weather conditions, and also improved irrigation sched-
uling due to better estimation of water use and more ap-
propriate timing of irrigations [10,28].
During the initial stage, there were no differences be-
tween the adjusted Kc (Kc-adj = Kcb·Ks + Ke) and Ke
values for the two treatments since the irrigation events
occurred at almost the same time suggesting a similar
crop development. However, the existing rule scheduling
approach adopted by the irrigation managers implies a
large irrigation interval (34 days between the second and
the third irrigation, and 14 days between the two treat-
ments for the third irrigation) which caused a decrease of
the Kc-adj and Ke values. In particular, the Kc-adj
reached a minimum value of 0.33 indicating a strong
water stress effect.
The stress coefficients Ks calculated for the two sur-
face irrigation treatments were also compared (Figure 3).
In the case of existing rule treatment, as explained pre-
viously, winter wheat experienced a water stress at the
crop-development stage due to the large irrigation inter-
Figure 2. Evolution of crop coefficients during the winter
wheat crop season under two surface irrigation treatments: (a)
full irrigation, (b) existing rule.
Figure 3. Estimated daily stress coefficient Ks by the FAO-56
dual Kc approach for full irrigation and existing rule treatments
during 2004-2005 growing season. Amounts and dates of irri-
gation applied for both treatments are also shown.
val, the Ks decreased below the threshold value for 10
days. Also, due to the insufficient water quantity applied
during the fourth irrigation event, the Ks started to de-
cline earlier than for the full irrigation treatment.
This experiment revealed that although the irrigation
scheduling adopted by the irrigation agency proposed
the same number of irrigation events as those required
by the FAO method used for the full irrigation schedul-
ing (five irrigations received throughout the season), the
irrigation timing and water amounts were not optimal
suggesting an inadequate water irrigation delivery. In
fact, in Haouz irrigated schemes, as previously explained,
the irrigation depths are defined for each irrigation cycle,
in an equitable manner (a fixed-area proportionate water
amount for all farmers) according to the water availabil-
ity in reservoirs irrespective of the crops and their
growth stages.
3.3.2. Soil Water Depletion
The crop water stress is also appreciated by analyzing
the root zone soil water depletion (Dr) during the crop
season. Figure 4 illustrates Dr estimated by the FAO
procedure for the two treatments: full irrigation treat-
ment (Figure 4(a)) and existing rule treatment (Figure
The total available water (TAW) curve increases dur-
ing the crop season regarding the root development
which reached a maximum value of 0.80 m according to
the root depth measurements made during the season.
The readily available water (RAW) curve shows some
variations during crop season due to the ratio of RAW to
TAW parameter “p” which varies with the daily crop
Since the 2004-2005 season was dry (with a precipita-
tion of 116 mm from September 2004 to August 2005
which is lower than the regional climatic average of 240
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Figure 4. Daily estimated root zone depletion (Dr), Total
available water (TAW) and readily available water (RAW) for
two treatments: (a) full irrigation and (b) existing rule. Rainfall
and irrigation are also plotted in the same figure.
mm), it can be noticed that the rainfall throughout the
growing cycle has slightly contributed to the soil water
moisture and the irrigation has played an important role
in the soil water depletion reduction (Figure 4). How-
ever, the two peaks of precipitation (14 and 22 mm re-
spectively) that occurred on 59th and 63th day after sow-
ing (DAS) have reduced the soil water depletion without
cancelling it. Thus, Dr was maintained close to RAW in
the case of full irrigation treatment during this period
and it was lower for existing rule treatment suggesting
acceptable soil moisture level since the third irrigation
water was still stored in the soil contributing to the crop
In addition, for existing rule treatment, the water de-
pletion Dr exceeded the RAW for a long period (be-
tween the 57th and the 71th DAS) and also the fourth ir-
rigation depth applied on 102th DAS was not sufficient
to meet the actual Dr and offset the depletion resulting in
a deficit irrigation condition. This has affected the crop
development and productivity (see section 3.4). Finally,
the soil root zone water depletion seems to be fairly well
simulated by the model since it was updated only two
times throughout the season (33th and 85th DAS) for the
two treatments.
3.4. Grain Yield and Water Use Efficiency
The grain yields and Water Use Efficiency obtained
for the different irrigation schedules are shown in Table
3. Regarding the grain yield, it was 50, 39 and 62 quin-
tals/ha for the three treatments (full irrigation, existing
rule and Drip irrigation) respectively. It was observed
that the grain yield obtained with drip irrigation was
24% higher than full irrigation treatment and 59% higher
than the existing rule treatment. In addition, with exist-
ing rule treatment, there was a significant reduction in
the crop yield. Indeed, the yield reduction obtained was
about 22% in comparison with the full irrigation treat-
ment, which shows the negative effects of the rules
adopted by the managers for irrigation scheduling at
scheme level on the crops productivity.
The low yield obtained with existing rule treatment
could be explained, as previously highlighted, by the
crop water stress since all crop management factors were
similar for all treatments. Indeed, the water stress was
caused by the large irrigation interval on February which
occurred during the stem extension stage and reduces the
number of heads/m2 (up to about –11%) in accordance
with previous findings [29,30], and by the insufficient
water amount applied in March which occurred during
the heading and flowering stage and coincided with high
ETo values, affecting the grain formation especially the
number of seeds/head. This result was consistent with
the findings of [20], who reported that the most sensitive
stage of winter wheat to water stress was from stem
elongation to booting, followed by anthesis and grain-
The WUE was 0.99, 1.17 and 1.50 Kg/m3 for the three
treatments (full irrigation, existing rule and drip irriga-
tion) respectively. With surface irrigation, the WUE was
improved by 18% when irrigation is scheduled optimally
according to FAO method as compared with existing
rule treatment. Drip irrigation showed better result since
the WUE was improved by 52% and 28% when com-
pared with surface irrigation respectively the existing
rule and full irrigation treatments.
These results revealed that high water use efficiency
Table 3. Grain yield and WUE for the three irrigation treat-
Full irrigation Existing rule Drip irrigation
Grain yield
(quintals/ha) 50 39 62
WUE (kg/m3) 1.17 0.99 1.50
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could be achieved either by improving yield and saving
water under drip irrigation system. Also, even with sur-
face irrigation method, good management of irrigation
water (i.e. better irrigation scheduling) could lead to a
better water use efficiency. The values obtained are close
to those found in other studies [4,20,31-34]. It was re-
ported that in general, the wheat WUE ranges from 0.40
to 1.83 kg/m3 globally on a yield basis. For example,
with the irrigated wheat in the US southern plains, WUE
was 0.50 - 1.20 kg/m3 with a yield of 3000 - 8000 kg/ha
[4,31,32]. A higher WUE of 0.70 - 1.51 kg/m3 in winter
wheat was found in the North China Plain [20,33,35].
Recently, [32] reported a much higher WUE of 0.97 -
1.83 kg/m3 in winter wheat in the North China Plain
(NCP). With drip irrigation, WUE values of 1.13 - 1.20
kg/m3 for wheat were found in North Sinai (Egypt) de-
pending on the drip system adopted [6]. A high effi-
ciency of water use is extremely important for farmers
and irrigation agencies in water scarce areas.
Irrigation schemes in semi-arid environment are gen-
erally subject to rotational irrigation supply based on
fixed-area proportionate water depths applied every irri-
gation cycle irrespective to crops and their growth stages.
In this study, a dedicated experiment was conceived and
implemented to evaluate the effects of the existing rule
of surface irrigation allocation and scheduling in such
rotational irrigation systems on yield and water use effi-
ciency of winter wheat compared to a full irrigation ap-
proach and the drip irrigation method, both based on
FAO-56 procedure. The results showed that irrigation
scheduling methods had obviously significant effects on
growth and yield of winter wheat.
For surface irrigation, the existing rule approach re-
sulted in yield and WUE reductions of 22% and 15%,
respectively, compared with optimized irrigation sched-
uling proposed by the FAO-56 for full irrigation treat-
ment. This revealed the negative effects of the irrigation
schedules adopted in irrigation schemes under rotational
water supply on crops productivity. Considering the ab-
solute necessity for water saving and sustainable food
production, it can be recommended to irrigation manag-
ers to move from equitable, and rigid delivery schedules
to more flexible delivery system operation and crop-
based schedules.
The results also suggested that incorporating remote
sensing-based vegetation indices, such as NDVI, used to
derive Kcb for the FAO method provides an opportunity
to improve irrigation scheduling by a better estimation of
water use and a more appropriate timing of irrigations.
This study has demonstrated also that drip irrigation
could be applied to the wheat crop, usually cultivated in
rotation with other crops, which may justify the drip
irrigation system adoption by farmers but economic pa-
rameters are to be considered more closely.
It is also demonstrated, as expected, that drip irriga-
tion applied to wheat was more efficient with 20% of
water saving in comparison with surface irrigation (full
irrigation treatment). Drip irrigation gives also higher
wheat yield compared with surface irrigation (+28% and
+52% for full irrigation and existing rule treatments re-
spectively). The same improvement was observed for
water use efficiency (+24% and +59% respectively). It
can be recommended that, flexibility of on-farm irriga-
tion scheduling can be improved by providing a storage
capacity (reservoirs) below the delivery point, so as to
compensate for the expected mismatch, especially in
time, between deliveries and consumption. Water can be
pumped from the reservoir, which implies additional
investment and operating costs but may allow the appli-
cation of drip irrigation and also the conjunctive use of
groundwater with the surface water when this latter is
not available.
This study was supported by SUDMED (IRD-UCAM) funded by
the European Union (PCRD). The authors thanks the SudMed techni-
cal partners especially ORMVAH (‘Office Regional de Mise en Valeur
Agricole du Haouz’, Marrakech, Morocco) for its technical help and
for access to use the field site.
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