International Journal of Agricultural Policy and Research Vol.3 (8), pp. 328-336, August 2015
Available online at http://www.journalissues.org/IJAPR/
http://dx.doi.org/10.15739/IJAPR.057
Copyright © 2015 Author(s) retain the copyright of this article
ISSN 2350-1561
Original Research Article
Crop coefficient and water requirement for wheat
(Triticum aestivum) in different climate regimes of
Algeria
Received 17 July, 2015
*1Laaboudi A., 2Allaoua C.,
3Hafouda L., 4Ballague D.,
2Sbargoud S., 5Meterfi J
and 2Herda F.
1Algerian Institute for Research in
Agronomy. Experimental Station of
Adrar, Algeria.
2Algerian Institute for Research in
Agronomy. Experimental Station of
Mahdi boualem, Algeria.
3Algerian Institute for Research in
Agronomy. Experimental Station of
Touggourt, Algeria.
4Algerian Institute for Research in
Agronomy. Experimental Station of
Lahmadna, Algeria.
5Algerian Institute for Research in
Agronomy. Experimental Station of
Lamtar, Algeria.
*Corresponding Author
E-mail: [email protected]
Tel/fax: 213 49 96 83 85
Revised 24 July, 2015
Accepted 27 July, 2015
Published 8 August, 2015
Algeria is an agricultural country where wheat is the staple food of this
region. Winter wheat growth stages start from November and normally end
in May. Better management of limited water resources is the main objective
of this study. For this aim, we have used FAO Penman-Monteith Equation to
assess reference evapotranspiration and non-weighing lysimeters in five
experimental stations, located in different climatic zones of the country to
determine wheat water balance. Results showed that wheat crop water
requirement followed variations in terms of location and season. The north
of the country receives good rains during growth stages of wheat. In the semi
arid area which is the largest part of the country, where the winter wheat is
cultivated, precipitation is always lower than water crop satisfaction.
Consequently, irrigation may be required. In the south of the country where
precipitation is negligible, irrigation is necessary. Further, Maximum
evapotranspiration of wheat (ETc) varies according to the growing stages
from 1mm /day to 2.6 mm/day in sub humid region and from 2.14 mm/day
to 9.43 mm/day in hyper arid region. Crop coefficient values vary from 0.78
to 1.04 in sub humid region and from 0.50 to 1.35 in hyper arid region.
Key words: Winter wheat, non-weighing lysimeters, climatic zones, maximum
evapotranspiration, crop coefficient.
INTRODUCTION
The great challenge for the coming decades will be the task
of increasing food production to ensure food security for
the steadily growing population. However, the dependency
on water for food production has become a critical
constraint for increasing food production in many regions
face serious water deficiency (Zhao et al., 2005; Clemmens
and Molden, 2007). So, according to Naeem and Rai (2005),
water shortage requires to develop new technologies and
methods of irrigation able to utilize more effectively this
precious resource. On the other hand, there is also a need to
achieve higher water use efficiency and to increase water
productivity of existing water (Bharat, 2006). This
necessitates innovative and sustainable research and an
appropriate transfer of technologies (Pereira et al., 2002).
It should be noted that in many regions of the world,
climate changes will increase the average reference
evapotranspiration by 2% (De Silva et al., 2007) and then
increasingly affects cultivation water requirements (Doria
et al., 2006).
In Algeria, there is a lasting issue to meet growing
irrigation demand despite government investments to
mobilize additional water supplies for domestic, industrial
and agricultural use. Recent droughts have exposed the
vulnerability of large-scale irrigation systems and the
pressure on groundwater resources. At the same time, new
demands are emerging for major investment in wastewater
treatment (World Bank, 2007).
Available water appears to be the most important factor
limiting high yields in wheat crop production in semi- arid
regions of Algeria (Chennafi et al., 2006). That is why,
Int. J. Agric. Pol. Res.
329
Lahmadna
(Semi arid 1)
Algiers (Sub humid)
Touggourt (Arid)
Lamtar
(Semi arid 2)
Adrar
(Hyper arid)
Figure 1: Sketch of the investigation areas
development of more water sources for irrigation, its
infrastructure and improvement of planning system as part
of the small-scale irrigation project activities appears to be
the coming challenges for decision makers. In arid regions,
recently, thousands of hectares are irrigated by pivot
centers without knowledge of crop water requirement (Liu
et al., 2010). This has affected the groundwater level to
decrease. Therefore, the accurate estimation of crop water
requirements in the arid and semi-arid regions is crucial for
a better water-use efficiency (Er-Raki et al., 2011) and
better planning of irrigation scheme, irrigation scheduling,
effective design and management of irrigation system
(Hajare et al., 2008).
Reference evapotranspiration is an important quantity
for computing the irrigation demands for various crops
(Chowdhary and Shrivastava, 2010; Dinpashoh, 2006).
Current irrigation schedule is based on a well‐established
crop coefficient and on reference evapotranspiration
procedures to estimate daily crop evapotranspiration
(Hunsaker et al. 2007); that is why, a poor ET calculation
appeared to be associated with poor estimations of the ET0
(Shujiang et al., 2009). Knowing ET0, crop coefficient
methodologies are widely used to estimate actual crop
evapotranspiration (ETc) (Douglas, 2005).
The main objective of this study is to determine the water
need of wheat during different growth stages and water
deficiency in different climate regimes of Algeria.
MATERIAL AND METHODS
Site Description
Experiments were conducted in five experimental stations
of Algerian institute for research in agronomy. They are
located in different agro climatic zones (Figure 1).
Each experimental station is equipped with weather
station. Daily climatic data sets for the period of three
campaigns (2004/2005, 2005/2006 and 2006/2007) were
collected in each location. They were composed of
minimum and maximum temperature (°C), relative
humidity (%), wind speed (m/s), sunshine duration
(number of hours/day), net radiation (Wm-2) and rainfall
(mm).
Climate characteristics
The most important character which characterize the study
areas are amounts of rainfall. Thus, during vegetative cycle
of wheat, amount of rainfall in sub humid region as Algiers
(Mahdi Boualem station) is higher than 637 mm. Semi arid
region as Lahamadna and Lamtar are characterized by low
and erratic rainfall of up to 500 mm per annum and
periodic droughts. During the growing stages of wheat,
amounts of precipitation were between 465 and 363 mm.
In the arid zones; Touggourt and Adrar, rainfull is
Laaboudi et al.
330
Table 1 .Locations, Water and fertilizer management of the five stations
Stations
Locations and
elevation (m)
Water management
Algiers
36° 41' 41' 19"
N, 3° 6' 41" E
and 18.5
35°54' N, 00°
47' E and 46
35° 04' N, 0°
48' E and 571
33° 04' N
06°05' E, and
75
27° 49' N, 00°
18' E and 278
Without irrigation
Lahmadna
Lamtar
Touggourt
Adrar
Fertilizer management
Pre plant supply
Post plant supply
(q/ha)
(q/ha)
P
1
K
1
N
3
Supplemental irrigation with
sprinkler system
Supplemental irrigation with
sprinkler system
full irrigation with flood
irrigation
1
1
2
1
1
1
1
0
3
full irrigation with flood
irrigation
3
1
3
P: Phosphorus (Treble superphosphate 46 %), K: Potassium (Potassium sulfate 50 %),
insignificant; it is lower than 100 mm/year. During
vegetative cycle of wheat, there are only 54 and 15 mm at
Touggourt and at Adrar respectively.
lysimeters. They were used for the water balance
estimation.
Water and fertilizer management
Soil type of the five stations
The soil type differs from one station to other, it is Silty clay
soil for Algiers and Lahmadna, loamy clay soil for Lamtar,
sandy loam soil for Touggourt and Sandy soil for Adrar.
Water and fertilizer management differ from one location
to another. In arid region, full irrigation is practiced, while
in semi arid region only of precipitation is directly used for
wheat crop irrigation. Also, fertilizer management differs
from one location to another (Table 1).
Estimation of reference evapotranspiration
Crop evapotranspiration of wheat (ETc)
The reference evapotranspiraiton was calculated using the
Penman-Monteith equation (Allen et al. 1998).
900
0.408( Rn  G )  
u2 (es  ea )
T
 273
(1)
ET 0 
   (1  0.34u2 )
Where:
ET0 - reference evapotranspiration [mm day-1], Rn - net
radiation at the crop surface [MJ m-2 day-1], G - soil heat flux
density [MJ m-2 day-1], T - mean of daily air temperature at 2
m height [°C], u2 - wind speed at 2 m height [m s-1], es saturation vapour pressure [kPa], ea - actual vapour
pressure [kPa], (es - ea) - saturation vapour pressure deficit
[kPa], ∆ - the slope vapour pressure curve [kPa °C-1], γ the psychometric constant [kPa °C-1].
The required meteorological parameters were provided
directly by weather stations located inside the research
farms. Daily meteorological parameters are recorded and
used for computing reference evapotranspiration.
Experimental treatments and measurements
Experiments on winter wheat were conducted in three
consecutive winter wheat seasons in 2005–2007. In each
experimental station, there were four non-weighing
The daily crop evapotranspiration (ETc) values of wheat
were determinated by non-weighing lysimeters. Using the
water balance, ETc is the difference between the input
water and output water.
Lysimetry in its simplest form involves the volumetric
measurement of all incoming and outgoing water of a
container which encloses an isolated soil mass with
vegetated surface. This incoming and outgoing water flux
can be represented in a water balance, expressed as;
P  T  Ro  ETc  D  W
(2)
The incoming water flux for a given time period refers to
P = precipitation and I = irrigation
The outgoing water flux refers to ETc = maximum
evapotranspiration of the crop and D = drainage water.
Ro and ∆W are respectively surface runoff and
change of water content (w) of the isolated soil mass over a
given period. In our case these two terms are null and ETc
can then be determined directly by:
ETc  P  I  D
(3)
Each lysimeter has 1 meter depth and 2 meters of
diameter (Figure 2). The special arrangements are made
within the lysimeter to drain and measure the water
percolating through the soil mass. A special drainage
Int. J. Agric. Pol. Res.
331
1
ETc
Soil
Sand
Gravel
22
Figure 2: Scheme of two non weighing lysimeters
chamber and calibrated container is used to collect and
measure the percolated water.
Crop coefficient
The measured wheat evapotranspiration (ETc) together
with reference evapotranspiration (ET0) were used to
calculate the crop coefficients.
Kc 
ETc
ET 0
(4)
where ETc is maximum evapotranspiration of wheat
(mm) for a given period and ET0 is reference
evapotranspiration (mm) in the same period.
Average values of precipitations
The meteorological data were collected from weather
stations of Experiment farms. Average values of
precipitation (mm) during growing season of wheat in
different experimental locations are presented in Figure 3.
RESULTS AND DISCUSSIONS
Reference evapotranspiration
Using FAO Penman-Monteith equation, the reference
evapotranspiration values during the growing season of
wheat for each studied location are shown in Figure 4.
These values are dependent on meteorological parameters
especially temperature and air humidity. That is why higher
values were obtained in hyper arid region and the lowers
were recorded in sub humid region.
Crop evapotranspiration (ETc)
The values of measured ETc over the growing season
during three test campaigns are depicted in Figure 5. As the
crop develops and shades more and more the ground,
evaporation becomes more restricted and transpiration
gradually becomes the major process. In semi arid region
(semi arid 2) for example, total water use during the
growing period of wheat were 480 mm, 499.6 mm and 494
mm respectively during first, second and third season.
These are higher than 427 mm (16.8 inches) reported by
Charles (2009) for wheat in central Arizona.
Total water used during the growing period ranged from
325 mm in sub humid regime to 738.58 mm in hyper arid
regime. Total water used for the three campaigns in arid
region are 592, 600 and 579 mm respectively. these are
closer to 624, 599, and 591 mm obtained by Douglas et al.
(2005) respectively during the first, second and third
season.
At the mid-season stages, the values of ETc are higher
than at other stages of wheat crop. These results are similar
to those of Bing et al. (2009) found that ETc increased with
the development of the growing season and reaches a
maximum when leaf area index (LAI) is greatest. Then it
decreased gradually (Figure 6).
Crop coefficients (Kc)
After determining ET0, the ETc or Crop Water Requirement
(CWR) can be calculated using the appropriate cropcoefficient formula (4).
Laaboudi et al.
Figure 3: Monthly precipitation (mm) during growing season of wheat in different experimental
locations (averages of study period (2004 - 2007)
Figure 4: Reference evapotranspiration values (mm/stage) during growing stages of wheat for the five
experimental regions
332
Int. J. Agric. Pol. Res.
333
Figure 5: Amount of water consumed by wheat during the vegetative stages (mm/stage) in
the study areas (average of three cropping seasons)
16,00
14,00
ETc (mm/day)
12,00
10,00
sub humid
semi a rid1
semi a rid2
a rid
hyper a rid
8,00
6,00
4,00
2,00
0,00
Emergence
Tiller
Stem
elonga tion
Hea ding
Flowering
milk -soft Ha rd dough
dough
Growing sta ges of whea t
Figure 6: ETc evolution according to growing stages of wheat
Crop coefficient (Kc) is actually the ratio of maximum crop
evapotranspiration to reference crop evapotranspiration.
For wheat, this ratio can reach 1.35 (hyper arid region)
during the reproductive cycle (heading to grain formation),
otherwise it remains less than 1 bearing minimum values
during the early age of the crop and at maturity (Figure 7).
The Kc of the young plants is low, and then it increases
gradually for reaching a maximum value for flowering
stage. Then it decreases thereafter. In sub humid and semi
arid regions, the highest values of Kc are 1.12 and 1.19
respectively. They are similar to 1.19 obtained by Gao et al.
(2009) and 1.24 reported by Tyagi et al. (2000). In arid and
hyper arid regions, highest values are 1.29 and 1.35
respectively.
They are closer to 1.42 obtained by
Yongqiang et al. (2004) and 1.44 obtained by Douglas et al.
(2005).
Climatic deficit
Water Requirement is mainly dependant on climatic factors
(air temperature, solar radiation, relative humidity and
wind velocity) and agronomic factor (crop development
Laaboudi et al.
334
1,4
sub humid
semi arid1
semi arid2
arid
hyper arid
1,3
1,2
Kc values
1,1
1,0
0,9
0,8
0,7
0,6
0,5
0,4
Emergence
Tiller
Stem
Heading Flowering milk -soft
elongation
dough
Hard
dough
Wheat growing stages
Figure 7: Evolution of Kc values of wheat in different regions of Algeria
Table 2. Water balance (mm) and satisfaction indexes (%) of different agro climatic zones (during experimental
campaigns)
Average of precipitation
Average of ETc
Water Balance
Satisfaction index
Sub humid
406
330
76
100
Semi arid 1
227
464
-237
49
stages) as well. The highest crop water needs are thus
found in areas which are hot, dry, windy and sunny (arid
and hyper arid regions). The lowest values are found when
it is cool, humid and cloudy with little or no wind (subhumid region). Thus one crop grown in different climatic
zones will have different water needs (Table 2). When
rainfall is less than water need, the crop experiences water
stress and both crop growth and final yield are affected
(Akram, 2011).
Satisfaction index (%) is the indicator which shows the
available moisture to sustain growth and development of
Wheat crop under different moisture regimes. Sub humid
(H) regions reflect the areas having amount of rainfall
greater than crop water requirements, means rainfall
fulfills 100% of the crop water requirement.
In semi arid zone, there are two cases; in Lahmadna
region (semi arid 1) satisfaction is 100% according to
normal average of precipitation, but during experimental
period it was only 49%. It was less than 54 % of Lamtar
(semi arid 2) where the normal satisfaction index is 74%.
Arid and hyper arid zones are located in Sahara region
where the precipitations are negligible and irrigation must
be arranged during the entire crop vegetative cycle.
Semi arid 2
265
491
-226
54
Arid
26
590
-564
4
Hyper arid
7
738
-731
0.90
During the three experimental campaigns there were water
deficits; water balances were negative for all locations
except sub humid region that has not required irrigation.
Under both locations of semi arid conditions, the irrigation
was arranged for the proper maintenance of crop growth.
It should be noted that even satisfaction index is greater
than 50 %, it must be take into consideration the
disturbance of rainfall during growing stages of wheat and
also the precipitation effective which is 75% in Algeria.
November is the sowing month for wheat crop in most
parts of the country; the precipitation amounts are 84 mm,
55 mm and 42 mm in Algiers, Lahmadna and Lamtar
respectively. These quantities are satisfied the need of
water in emergence stage.
During the month of December, generally the northern
half of the country receives precipitation more frequently
and with more amount as comparing to the southern half.
Further, at this moment water requirement of wheat are
lower.
In January, temperature decreases below zero °C in some
parts of Algeria especially in semi arid regions (Lahmadna
and Lamtar). Due to decrease in evaporative demand, this
rainfall becomes very helpful to reduce water demands.
Int. J. Agric. Pol. Res.
335
Nevertheless, while northern parts have favorable moisture
conditions for wheat crop, southern parts of the country
remain dry and under water stress. The precipitation
quantities are 117 mm, 86 mm and 62 mm respectively for
Algiers, Lahmadna and Lamtar. But there are only 7 mm for
Touggourt and 3 mm for Adrar.
In February, wheat crop is at stem elongation stage. The
water consumption increases to reach 2.58 mm/day
(Lamtar) and satisfaction index decreases down to 72.9%.
A supplemental irrigation could be planned in order to
stabilize or improve yield, while, in Algiers and Lahmadna
locations, water requirement are lower than precipitation
and satisfaction index is 100 %.
In March, heading and flowering stages occurred. This
month is very important for wheat crop, because the water
requirement increases and continues to increase up to
maturity; if stress is observed during this month then crop
yield may suffer. In most parts of semi arid region, water
stress observed unlike in Algiers where conditions remain
favorable even its satisfaction index is 87%. While in both
location of semi arid region (Lamtar and Lahmadna),
irrigation is necessary.
In April and May, due to dryness of air, low humidity and
high temperature; water demand is high, consequently
water requirements increase significantly. Satisfaction
indexes are lower than 50% for almost all locations,
consequently irrigation is required.
CONCLUSIONS
Using non-weighing lysimeters and meteorological
parameters collected on sites, this work is the first of its
quality, which brought together a large number of
researchers located in different bioclimatic zones of Algeria.
Furthermore, through this work the amounts of water
actually consumed by wheat are known, thus, the water
deficit and amount of supplemental irrigation could be
estimated with satisfactory accuracy especially in semi arid
zones.
The amount of water used by winter wheat is linked with
meteorological parameters. They are very high in hyper
arid and arid regions, moderate in semi arid region and low
in sub humid region.
In arid regions, because precipitation is negligible and
satisfaction index is very low, irrigation is necessary during
the whole wheat crop cycle. In semi arid region, despite of
satisfaction index may be close to 100 %, special attention
should be taken, because disturbance in rainfall
distribution can frequently occurs what can provoke a
significant yield loss. In these conditions supplemental
irrigation is required, especially in months of April and
May. In sub humid region, always precipitation is higher
than water requirement of wheat thanks to good rainfall
and climatic demand which are very low due to low
temperature and moderate humidity. It should be taken
into consideration the effective precipitation which could
vary according to the time and space.
Acknowledgement
First of all we are thankful to Ministry of Higher Education
and Scientific Research for their financial and logistical
support and for providing necessary guidance concerning
projects implementation. We are also grateful to Algerian
Institute for Research in Agronomy for provision of
expertise, and technical support in the implementation.
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