Irrigation Water Quality Criteria for Wheat in SemCArid Areas of Syria
by
JINAN HAFFAR
A thesis submitted to the Faculty of Graduate Studies and Research, in partial fulfilment
of the requirements for the degree of Master of Science
Department of Agricultural and Biosystems Engineering Macdonald Campus of McGill University Ste-Anne-de-Bellevue, Quebec, Canada
March 1997
O JINAN HAFFAR, March 17,1997
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ABSTRACT
A field study was conducted for two yean in three semi-and regions of Syria
in order to define. under field conditions. the wheat (Triticum aestivium L.) yield
response function to imgation water salinity and to study aie process of soi1 salt
accumulation. The three regions experience sirnilar climatic conditions (semi-arid
Mediterranean dimate) but have different soi1 textures, varying from sandy barn to
clay. The study involved 74 farms al1 of which had been imgating for more than 3
years prior to this study, with well water of different salinity values (0.44 to 14.1
dç/m).All of these farms operated with similar cultural pracüces.
Results indicate that the Hiheat yield response function to irrigation water
salinity differs between the three regions.The imgation water threshold salinity
value beyond which wheat yield started to decline. was found to be 6.5 d S h , 3.5
dçlm and 1.2 dS/m in the Khabur low plains, Aleppo south plains and Shedadeh
area respectively. Wheat was more salt tolerant to imgation water salinity in sandy
loam soils than clay loam soils. The three threshold values obtained in this study
are different from the 'universal" value of 4 dS/m which is proposed in current
l iterature. The 'universaln value was obtained from artificially salinized field plots
seeded under non-saline conditions.
In addition, it was found that salt accumulation in the soi1 profile increases
as sail clay content increases.
The resuits deronstrate the necessity of establishing regional water quality critena
when planning the use of saline water sources for imgation in serni-and regions.
RÉSUMÉ
Une étude auchamps a été réalisée dans trois régions semi-arides de la
Syrie pour déterminer la réponse de la productivité du blé (Triticurn aestivium L.)
à la salinité de I'eau d'irrigation et pour étudier le phénornéne de l'accumulation du
sel dans le sol.. Les trois régions étaient sous les mêmes conditions climatiques
mais avaient une texture de sol différente qui variaient entre sableux-limoneux à
argileux. L'étude couvrait 65 fermes utilisant pour plus de trois ans de I'eau
souterraine saline variant entre 0.44 dam et 14.4 dS/m et qui appliquaient les
mêmes pratiques agricoles.
Les resuitats indiquent que la réponse de la productivité du blé à la salinité
de I'eau d'irrigation diffère largement entre les trois régions. Le blé était plus
tolérant pour la salinité de I'eau d'irrigation dans le sol sableux-limoneux que dans
le sol argileux. La valeur limite de la salinité de l'eau au-dessus de laquelle la
productivité commence à décroitre était de 6.5 dS/m et 1.2 d a m respectivement.
La plus faible valeur était dans le sol argileux. Ces trois valeurs limites sont
différentes de la valeur universelle de 4 dSim qui est proposée dans la litérature et
qui est obtenu à partir des essais sur des parcelles artificellement salinisées.
En plus, il a étè trouvé que le degré de la salinisation du sol est relie au
nuveau d'argile existant dans le sol, augmentant avec l'augmentation du
pourcentage d'argile.
Ces résultats démontrent la nécessité d'établir un critere régional pour la
qualité de I'eau pour l'exploitation des nappes aquifères salines en irrigation.
I would first like to present rny appreciation and thanks to my thesis supervisor, Dr.
Robert üonnell, for the assistance, advice and support he has provided throughout
this thesis.
I would also, at this time, like to thank Professor R. Broughton for his continuous
advice and encouragement during my study.
Very special thanks are owed to my husband Professor Michel Wakil for his help
and to rny children Georges, Naji and Suzanne Wakil for their support, patience and
encouragement during this study.
Acknowledgment is also extended to Mt. Molrnajid Liaghat for his assistance and
advice. Thanks as well to al1 rny colleagues Humberto PizarroGarbone and Leif
Trenholrn. Kamran Davary, Mohamed Moussavizadeh, Sandra Ibara, Bano Mehdi,
Kathy Senecal, Manuel Mejia and the Administration staff for their encouragement.
I would like to thanks also Mr. Ante Rokov for his help in the computer center, and
Mrs. France Papineau for her help. I also wish to thank Mr. lskandar Debs for his
help. The author would also like to appreciate Mr. Georges Dodds for his English
corrections.
The project was sponsored by the International Centre for Agricultural Research
in the Dry Areas (ICARDA). I would like to express my gratitude to Dr. Mike Jones,
leader of the Fam Resource Management Program. and Dr.Thieb Oweis, Water
Management Specialist, for their help and assistance and to all CARDA
technicians who participated in soi1 end well water sample collection . I owe a big thanks to rny parents for their support. Finally I would like to thank Dr.
S. Kermasha as an extemal examiner for an invaluable review of the Thesis.
Tenns and Abbreviations Used
O C temperature degree, Celsius
Ca calcium
B boron
~oule/crn~/h r Joule/per square centirneter/per hour
centimeter
centimeter(of water pressure) per centimeter
cubic centimeter (of water) per gram
depth of irrigation application
deciSiemen per rneter
soi1 salinity, electrical conductivity of saturated extract
irrigation water salinity, electrical conductivity
irrigation water salinity threshold value
potential evapotranspiration
crop water requirements
hectare
soi1 water holding capacity (cmlcm)
sprinkler intensity (mmhr)
kilogram per hectare
crop coefficient
soif infiltration capacity at saturation (mmhr)
rn
Mg
mm
mrnlday
Na
P
Pe
PH
S
SAR
t
t/ha
iIJ
8
e t
Y
Yr
kiloPascal (kPa)
leaching fraction
meter
rnagnesium
millimeter
mil l i meter/day
sodium
rainfall (mm)
effective rainfall (mm)
acidity index
percent yield reduction per unit salinity increase
sodium absorption ratio
soi1 salinity threshold value
tonlper hectare
water potential (Pa)
water content (cm3/g)
water content at saturation (cm3/g)
yield (of wheat ma)
relative yield
TABLE OF CONTENTS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . INTRODUCTION 1
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . 1 Objectives 3
1.2scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 . LITERATURE REVlEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Crop sait toknnce of some crops as obtained under field
conditions
2.3 Field factors affecting crop salinity response . . . . . . . . . . . . . 10
. . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.1 Initial seed bed salinity 10
2.3.2 Use of saline water during germination and early seedling
stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.3 Leaching fraction 15
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.4 Irrigation interval 17
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.5 Soil texture 18
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.6 Climatic conditions 20
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.7 Irrigation method 21
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4Summary 23
3 . MATERIALS AND METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.1 Site description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.1.1 Site locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.1.2 Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.1.3 Soil characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
a) Soil texture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
. . . . . . . . . . . . . . . . . . . . . . . . b) Physical characteristics 30
3.1.4 Saline aquifers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.5 Agricultural practices 35
3.1.6 Irrigation methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
. . . . . . . . . . . . . . . . . . 3.1.7 W heat irrigation water requirement 37
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Fam selection 38
3.3 The general approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.4 Data collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3.4.1 Well water salinity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.2 Wheat yield 43
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.3 Soil samples 44
4 . RESULTS AND DlSCUSSlON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
4.1 Statistical analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Salinity threshold values 46
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Analysis of results 51
vii
4.3.1 Effect of soi1 texture and structure on irrigation water salinity
thresholdvalue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
4.3.1.1 Development of salinity profiles in the three
locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
a . Soi1 salinity development . . . . . . . . . . . . . . . . . 52
b . Regression analysis . . . . . . . . . . . . . . . . . . . . . 76
. . . . . . . . . . . . . 4.3.1.2 Seed bed salinity at sowing time 78
. . . . . . . . . . . . . . . . . . . . . . . . . 4.3.1.3 Natural leaching 81
4.3.1.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
4.3.2 The discrepancy between the obtained irrigation water
. . . . . . . salinity limits and the universal guidelines value 86
4.3.2.1 Use of saline water during early growth stages . . 87
. . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2.2 Leaching fraction 89
4.3.2.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 . SUMMARY AND CONCLUSlONS 92
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 Summary 92
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Conclusions 93
6 . RECOMMENDATIONS FOR FUTURE RESEARCH . . . . . . . . . . . . . . . . . . 97
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
viii
APPENDICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I l l
Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
Appendix 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix C 129
LIST of FîGURES
Figure
2.1
3.1
3.2
Page
W heat production function, (Mass&Hoffman) . . . . . . . . . . . . . . . . 6
Location of the studied areas . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Texture of typical soi! profile at Khabur valley plains,
Aleppo south plains & Shedadeh area . . . . . . . . . . . . . . . . . . . . 27
3.3, a Soil water characteristic, Khabur valley plains . . . . . . . . . . . . . . 31
3.3, b Soil water characteristic, Aleppo south plains . . . . . . . . . . . . . . . 32 3.3, c Soil water characteristic, Shedadeh area . . . . . . . . . . . . . . . . . . 33
3.4 Monthly distribution of rainfall (P) andwheat water requirernents
(EtJln Khabur valley plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Monthly distribution of rainfall (P) & water requirements (Etc)
In Aleppo south plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
The relationship between irrigation water salinity and wheat
relative yield, for two irrigation seasons in Khabur low plains . . . 47
The relationship bwtween irrigation water salinity and
relative yield, for two irrigation seasons in Aleppo south plains . 48
The relationship between irrigation water salinity and wheat
relative yield, for two irrigation seasons in Shedade area . . . . . 49
Soil salinity profile in Smehan and Nasserieh farms for rainfed
conditions, Khabur low plains . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
soi1 salinity profile in Nasserieh-l and Nasserieh-2 f a m , Khabur
lowplains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Soil salinity profile in Halelieh and Nasserieh-3 farms, Khabur low
plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Soil salinity profile in Thamad-2 and Bough-1 farms, Khabur low
plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Soil salinity profile in Thamad-1 and Bougha-3 farms, Khabur low
plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Soil salinity profile in JemAbiad and Dabbagieh farms, Khabur
lowplains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Soil salinity profile in Smehan Sharki and Smehan Gharbi fams,
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Khabur low plains 59
Soil salinity profile in Abou-Arzala and OumHajra farms, Khabur
low plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Soil salinity profile in Twahinieh and Eslamin farms for rainfed
. . . . . . . . . . . . . . . . . . . . . . . . . conditions, Aleppo south plains 61
Soil salinity profile in Eslamin and Al-Sharaf famis, Aleppo
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . south plains 62
Soit salinity profile in Tel-Tokan and Om Jran farms, Aleppo south
plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Soil salinity profile in Om-gharaph-1 and Om-Gharaph-2 fams,
Aleppo south plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Soil salinity profile in Om-Gharaph and Tel-Aran fanns, Aleppo
south plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Soil salinity profile in Hawawieh and Al-Raheb f a m , Aleppo
south plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Soil salinity profile in Khanasset and Qurbatieh famis, Aleppo
south plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Soil salinity profile in Shedadeh (for rainfed) and Al-Siha farms,
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shedadeh area 68
Soil salinity profile in Om Hajara-1 and Om Hajara-2 farms,
Shedadeharea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 9
Relationship between average Ece of the soi1 upper layer
(080crn) with the Ecw of the irrigation water in Khabur low
plains (clay) and Aleppo south plains (clay IoanJloam) . . . . . . . 72
Soil salinity-irrigation water salinity regression function in Khabur
basin and Aleppo basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ïï
Soil salinity profile at the end of the irrigation seasons in three
f a m at Khabur low plains (clay soil), Aleppo south plains
(clay loadioam soil) And Shedadeh area (loamlsandy loarn soil) 79
Soil salinity profile at the end of irrigation seasons and after
winter rainfall in a fam using water salinity of 14.1 d m ,
Aleppo south plains (clay loarrrcloam soil) . . . . . . . . . . . . . . . . . . 83
Reduction of soi1 salinity profile resulting from natural leaching in
Bougha farm, Khabur low plains . . . . . . . . . . . . . . . . . . . . . . . . . 84
LIST OF TABLES
Table (2-1) Typical Salinity threshold values 'Y found in the literature . . . . . . 11
Table( 3-1 a). Meteorological data . Hassakeh station. Khabur basin . . . . . . . . 28
Table (3-1 b). Meteorological data. Boueider station. Aleppo basin . . . . . . . . . 29
Table(3-2) Groundwater quality analysis frorn some wells in the three regions .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Table (4-1) Results of statistical analysis for the year 1993/1994 . . . . . . . . . . 46
Table (4-2) Results of statistical analysis for the year 1994/1995 . . . . . . . . . . 46
Table (4.3). Irrigation water salinity (ECJ and average soi1 salinity ( ECe ) of 0-80
cm in the studied fanns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Table (4-4) Wheat yield for various seeding rate. Shedadeh area . . . . . . . . . 81
Table (4 -5) Estimation of the applied leaching fraction in Khabur basin and
Aleppobasins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
xiii
1. INTRODUCTION
Due to an ever growing demand for water to satisfy the increasing need for
food production, saline [(with an electrical conductivity (EC) higher than 0.7 dSIm]
aquifers in Syna (Figure 3.1), a semi-and meditenanean country of limited water
resources (547m3/yr/person of available water), are becorning progressively
exploiteci for irrigation. During the last ten yean, approximately 150 000 ha. of new
land, about 20% of th9 current total inigated area in the country, have been brought
under irrigation using saline groundwater.
The major saline aquifers in Syria are located in two basins: the Khabur river
basin in the north east and the Aleppo basin in the central north. In both basins,
isolated confined aquifers contain saline groundwater.
In the Khabur basin, large saline aquifers exkt in the lower fiver valley plains
and in the plateau plains. It is estimated that more than 100 000 ha (Wakil, 1993)
in this basin are irrigated using saline groundwater. The saline aquifers in the
Aleppo basin are located in the southem part of the basin where about 12 000 ha
are irrigated with saline water. Saline groundwater in this area is used mainly to
irrigate winter crops (wheat) as an irrigation water source to supplement rainfall.
The use of saline water for irrigation under the semi-and and sub-desertic
climatic conditions prevailing in noraiern Syria affects the soil-plant system. The
climate in these areas is characterised by a short humid and rainy season
(November to February) followed by a long hot and dry summer (May to
September). The large annual excess of potential evapotranspiration (2500 mmlyr)
above rainfall (250 miJLr) resuits in a progressive build up of salts in the root zone.
This in tum leads to soi1 degradation and crop yield reduction, and to the
destruction of the local agro-ecosystem. Signs of soi1 deterioration have been noted
in several locations in the two basins.
Some of the first guidelines concerning the response of wheat to salinity were
developed at the US Safinity Laboratory Riverside, California by Ayers et al. (1 952)
and reported by Richards (1954), Maas and Hoffman (1977) and by Ayers and
Westcot (1 985). In Syria, these repoits pertaining to the tolerance of wheat and
other crops to salinity generally provide the guidelines used for the evaluation of the
use of saline groundwater for irrigation.
The upper limit value of water salinity for wheat (dunirn), that is the maximum
allowable water salinity without crop yield reduction, was reported by Ayers and
Westcot (1985) to be 4dSlm. This value was obtained from experiments performed
on artificially salinized field plots (silty-clay soil), seeded under non-saline
conditions and frequently irrigated (to rninimize the matric potential).
Current field research from a variety of agro-clirnatic regions in the world
indicate that, under local field conditions, wheat does not exhibit the degree of salt .
tolerance repoited by Ayen and Westcot (1 985). These reports show that different
factors, inctuding soi1 texture and structure, climate, irrigation water management
and agricultural practices affect wheat salt tolerance.
This dissertation examines wheat salt tolerance with respect to irrigation
water salinity and the developrnent of soi1 salt accumulation in the root zone, in
three ragions in northem Syrh where saline aquifers are intensively used for
irrigation. These regions are: the low valley plains of the Khabur river basin, the
Shedadeh plains in the Kahbur basin plateau and the southem plains of the Aleppo
basin. Soils in these regions Vary between clay and sandy loam.
This research project was sponsored by the International Centre for
Agricultural Research in the Dry Areas (ICARDA) in order to assess, under arid
conditions, the effects of using saline groundwater on soi1 salt accumulation and
crop yield and to define water quality criteria. This work is considered a first step
towards further research airned at developing suitable strategies for the safe use
of saline water for sustainable supplernental irrigation in the three regions.
1 .l Objectives
The objectives of this research project were to:
1. Deterrnine the wheat yield response to irrigation water salinity under local
field conditions of three regions located in semi-arid northem Syria. Define
the value of the irrigation water salinity limit (threshold value) for wheat in
each of these regions.
2. Assess the effect of soi1 texture and structure on the development of salinity
in the root zone. Relate the observed soi1 salinity to irrigation water salinity.
3. Assess the effect of soi1 texture and structure on the irrigation water salinity
limit for wheat (durum).
4. Assess the effect of irrigation water management on the irrigation water
salinity limit.
1.2 scope
This study examines the effect of using saline ground water on the soil-plant
system in three locations in Syna where a Mediterranean semi-arid climate prevails.
F A 0 (Ayers and Westcot, 1985) quality criteria for evaluation of saline water
are considered in this study. According to these criteria, water having an electical
conductivity higher than 0.7 dSlm is considered saline.
The results are only relevant to the conditions of this region:
- Mediterranean climate with an average annual rainfall of 250 mm;
- wheat (dunim) crop grown under supplemental irrigation conditions;
- traditional surface irrigation method (furrow basin);
- no surface or sub-surface drainage networks; and
- saline aquifers as the sole source of irrigation water.
The research work is based on field data collected from 74 fams selected
in the three regions during two agflcultural seasons (1 993-1 994 and 1994-1 995).
The data includes well water salinity and farm wheat (grain) yield. In addition, soi1
samples for salinity analysis were collected from 34 fams in the second year.
All the selected farms were using saline water for more than three yean prior to the
study. All farms applied similar irrigation water management and cultural practices.
2.1 Introduction
The conventional guidelines for crop salt tolerance evaluation reported by
Ayers and Westcot (1976 and 1985) and ASCE (1993), are based on two
parameters:
on threshold salinity" ( t ). This value represents the maximum allowable soi1
root zone salinity for which there is no crop yield reduction; and
- percent yield decline per unit of salinity increase beyond the threshold
value "su.
The relative crop yield ( Y,) for soi1 salinities ECe (electrical conductivity of
the saturated-soi1 extract) beyond the threshold value of "1" ( EC, > t ), can be
estimated using "the production function " model, (Figure 2.1). as presented by
Maas and Hoffman (1 9TI):
Yr- 100-s(EC,-t)
where €Ce is the mean electrkal conductivity (dS/m) of a saturated extract
taken from the root zone.
Salt tolerance data ( "s" and "tu ), for different crops. are given in
conventional guidelines (Maas and Hoffman, 1977). These data were generally
obtained from artificially salinized field plot techniques. Planting in these plots was
under non-saline conditions including non-saline seedbeds (soil of the experimental
Figure 2.1 Wheat production function in relation to irrigation water salinity (Mass & Hoffman, 1977)
plots was leached with fresh water before sowing) and irrigation with fresh water
during the early growth stages (germination and early seedling stages). Then
differential salination treatments (with water at a given salt concentration) were
gradually implernented after seedling establishment (François et al., 1 986). In
addition, in order ta eliminate soi1 water stress as an experimental factor and to
rnaintain soi1 salinity and soi1 water content relatively unifomi in the soi1 profile,
frequent irrigations with a high leaching fraction of about 0.5 were applied. Crop
yields were then conehted with the rnean salinity (EC,) of the crop root zone at the
end of the growing season.
In practice, under realistic field conditions, unifomiity is the exception rather
than the nile, and salinity may be present before the crop is established.
Furthemore, crops may have different sensitivities to salinity at different stages of
development.
Available reports from a variety of agro-dimatic regions in the worid indicate
that under local field conditions crops do not exhibit the degree of sait tolerance
reported by conventional guidelines. Due to field factors including agricultural and
irrigation practices in addition to soif characteristics, crops seem to have a much
lower salt tolerance than that suggested by the data presented by Ayers and
Westcot (1 985) and Maas and Hoffman (1 97ï) as "universal guidelines".
The objective of this chapter is to review various reports conceming field
studies of crop salt tolerance and to evaluate the effects of different practical
factors, related to field management and field conditions on crop salt tolerance.
These factors include : initial seedbed salinity, use of saline water during early crop
growth stages, leaching fraction levels, irrigation intervals, soi1 texture, climatic
conditions and irrigation methods.
2.2 Crop sall tolerance of some crops as obtained under field
conditions.
The conditions under which the "universal guidelines" data were obtained *
were, as outlined above, very ideal. In addition to the fact that salination treatments
were initiated in the late seedling stage, frequent irrigations with a high leaching
fraction were applied, which create steady state like conditions for both water and
salt soi1 solution flow (no change with time in sa1 and water content in the soi1 and
equal distribution of soil-water salinity in the root zone). The above conditions are
seldom realized in normal field operations.
Under efficient imgation conditions, where a low leaching fraction is applied,
and irrigation application infrequent, a steady state is not easily achieved. The
cornnon field condition, therefore, is the transient case where gradua! salinization
takes place duting the irrigation season (Rhoades. 1972) and where leaching may
occur abruptly and outside imgation season. Under such conditions, large spatial
and temporal variations in salinity in the root zone may be expected.
There are other factors in addition to spatial and temporal variability which
may influence the crop response to salinity. Among them are growth stages ( Maas
and Grieve, 1994; François et al., 1994; Van Hom, l99l), initial bed salinity ( Van
Hom ,199 1 ; François et al., 1 986), leaching fraction ( Bresler, 1 982; Rhoades, 1 972;
Bower, 1969) and soi1 texture ( Van Hom et al. 1993 ; Bhurnbla. 1976 ).
Therefore, under local field conditions (including agricultural and irrigation
management, climate, soi1 texture and structure). crop salinity response is largely
affected by the combined effect of al1 or soma of these factors. Reports are
available in the literature which indicate that crops under field conditions, are much
less tolerant to salinity than is presented by Ayers and Westcot (1985).
ûallantyne (1962) indicated that wheat in Saskatchewan (Canada) produced
a good yield with soi1 salinity values up to 3 dS/m and its yield was reduced by 50%
when exposed to soi1 salinity levels of 6.6 dSm. These values are rnuch lower than
the threshold value reported in the conventional guidelines (EC. of 6 dS/m for a
relative yield value of 100%). A field study conducted in the delta of Egypt showed
a threshold soi1 salinity value for wheat of 2.5 dS/m (Abdel Dayem et al.. 1989).
Measurernents of wheat yield and soi1 salinity from 86 farms in Haryana, India,
indicated that the threshold value averaged 3.5 dSlm (Osterbaan et a1.1991).
Resula from other agrodirnatic regions of lndia (Indore and Siniguppa) showed that
even under rnonsoon rain conditions, a reduction in yield of wheat in heavy textured
soils occunad when imgation water salinity exceeded 2 dS/m (Bhumbla, 1976). In
a recent study Minhas (1 996) reported that in the serni-and areas of India, threshold
irrigation water salinity has a value of 1 dS/m in a silty clay loam soil. In Pakistan,
H u m d i et al. 1980) and Makhdoom et al. (1 986) obtained maximum wheat grain
yield at an €Ce of 4 dSm, beyond which any increase in salinity had adverse effects
on yield. In a semi-and region of Syna (Al-Khabur region), Wakil and Bonnell
(1 996) reported that wheat in clay loamy soi1 has a threshold salinity value of 1.8
dWm. In the and region of Iraq, Hardan (19ï7) indicated that the threshold irrigation
water salinity level of wheat was 4 dS/m in a sandy loam soil.
McKenzie et al., (1 983) show that barley yield was reduced on average
8.8% per unit increase in EC., above an initial EC, of 2.2 dSfm. Fowler and Hamm
(1980), in a dryland experiment in Saskatchewan (Canada), found that the
reduction in barley yield averaged 10.1 % per unit increase in EC, above an initial
value of 3.6 dS/m. This rate of change in yield on saline soils in Saskatchewan is
similar to the data of Holm (1 978) which showed a 50% yield of bariey at an EC,
value of 7.8 dS/m. Wakil (1994) reported that in a sandy loam soi1 of a semi-and
region of Syria, barley yield started to decrease at an €Ce value of 4.5 dS/m. These
values are much lower than those reported by the conventional guidelines: "tU=8
dS/m and "s"-L;%.
ûther crops present the same trend of exhibiting lower Y' values in the field
compared to the universal guidlines values cited in the literature. This is the case
with mustard in India, (Minhas, 1996); soybean in Murrumbidgee Valley, Australia
(BeecherJ994); perenial pasture in Gulburn Valeey, Australia (Mehanni and
Respys,1986); and Cotton in Texas, U.S.A. (Thomas, 1980); China (Fang et
al., 1978); Uzbekistan ( Bressler, 1 979) and Pakistan (Ahmad et al., 1 991 ). Some of
these findings are surnmarized in Table (2-1).
2.3 Field factors affecting crop salinity nsponse
2.3.1 Initial seed bed salinity
In arid and semi-arid areas, where saline water is used for irrigation, an
initially saline seedbed is usually the result of salt accumulation from previous
irrigation seasons. The amount and extent of salt accumulated in the soi1 profile is
related to irrigation water salinity and soi1 texture and structure. Salt accumulation
in the soi1 profile increases as the irrigation water salinity increases (Hoffman et al.,
1983, 1989). In addition, for the same water salinity value, soi1 salt accumulation
increases as the clay component in the soi1 increases (Bhumbla, 1976).
Reports in the literature indicate that a saline seedbed adversely influences
germination percentage, crop establishment and ultimately crop yield.
Tabk (2-1) Typical Salinity threshold values "t" found in the literature
- Crop Y (dSlm) (1) T (dS/m) (2) Reference
W heat 6.00 1 -6 AICRP, 1994
4.0 Bhumbla, 1976
2.5 A.Dayem et al., 1989
3.0 Ballantyne. 1 962
1osterbaan et al., 1 99 1
4.0 Hummadi et ai., 1980
4.0 Makhdoorn et al., 1986
1.8 Wakil and Bonnell, 1996
I - - - .-
Mckenzie et al., 1983
3.5 Fowfer and Hamm, 1980
Cotton 7.7 2.0 Thomas, 1980
5 .O Bresler et al., 1 979
1 Pasture 1 1.8 ( 1.2 1 Mehanni and Repsys, 1986 I 1 1 1
(1) as given by Ayers and Westcot (1976) and F A 0 publication (1985).
(2) as obtained under field conditions.
Van Horn (1991) showed that saline seedbed delays germination. In the
case of sandy soil, the germination percentage of wheat decreases gradually as
seeâbed saiinity increases. (Germination percentage was 68% ,54% and 34% for
EC, seed bed salinity levels of 3.3, 6.6 and 10 dWm. respectively . In addition, he
indicated that plant root growth and activity is dramatically affected by seedbed
salinity. The actual evapotranspiration (ET,) of the seedling was greatly decreased
by increasing levels of initial soi1 salinity. As a result, plant growth during the early
seedling stage was greatly reduced: the relative growth of wheat and sorghum (salt
tolerant crops) declined by 32% and 47% respectively when planted in a sandy
saline seed bed with an €Ce of 3.3 dS/m. In general. his study concludes that
during earîy seedling growth, wheat and sorghum appear to be less tolerant than
during later growth stages.
Similar results have been obtained by François et al. (1 986). Their results
showed an average reduction of wheat seed germination of about 50% for an €Ce
seed bed salinity value of 8.8 dS/m, h i l e at 12.9 dWm, the germination percentage
dropped to only 8%.
Saline seedbd conditions adversely influence crop productbity (Minhas and
Gupta, 1993; Naresh et al., 1993; Beecher, 1991 ; Rains et al., 1 987; and Bernstein
et al., 1974). Minhas and Gupta (1993) showed a 30% decrease of wheat yield
when seedbed salinity increased from 3 to 8 dS/m.
Meiri (1 990) reports that cotton production function in response to salinity
depends on initial seedbed salinity. His study found specific yield functions for each
seedbed salinity value. The lowest yield corresponds with the highest seedbed
salinity value. In addition, Meiri's study indicated that the cotton salinity threshold
value ( t ) depends on initial seedbed salinity level.
2.3.2 Use of saline mer during germination and eady seedling stages.
Germination, emergence and early seedling growth are the most critical
periods for a crop to obtain a good stand. Losses in plant density during this penod
cannot be cornpensated for and will cause an equivalent loss in production. Under
saline irrigation conditions, either with saline water or on saline soil, the crop
generally encounters more problems dunng germination. emergence and early
seedling growth than during later growth stages and may even fail to get
established. In fact, failure to obtain a good stand of plants is often the factor that
most limits crop production in saline areas. Once the stand is established.
management risks are generally substantially reduced (Rhoades and Loveday,
1990). The essential difficulty is the high salinity in the top layer of the soi1 profile.
This exposes the gerrninating seed and seedling to a much higher salt
concentration than at later growth stages.The high sait concentration in the top
layer occurs because during germination and emergence almost al1 water loss is
caused by evaporation from bare soi1 and that during the young seedling stage the
root system is still shallow and water uptake by the plant is rnainly limited to this top
layer. The water loss from the top layer causes high salt concentrations. partly
through a sharply reduced moisture content and partly through an increase of the
salt content due to salt solution capillary transpoit from the underlying layers.
An extensive field study on soi1 salt distribution resulting from the use of
saline irrigation water was made by Bernstein et al. (1 955), Bernstein and François
(1973, a), Miyamoto (1985,1989) and van Hom (1991). They showed the formation
of an excessive localized salinity in the seed bed ( soi1 top layer ) which exceeded
by more than twenty fold the irrigation water salinity applied on the soi1 surface.
Bernstein and François (1973,a) indicate that even when using low salinity
water (EC,= 0.6 dS/m). salt concentration on furrow-imgated fields may reach as
high as 10-25 dS/m in the top layer of soi1 (O - 10 cm).
Van Hom (1 991) shows that during germination and eariy seedling stages
salt concentration in a sandy soi1 top layer ( 0-5 cm ) may reach a value ten times
more than the initial salt concentration. His study also showed that this problern was
amplified by increasing initial seedbed salinity.
Salt accumulation in the soi1 top layer during germination and early seedling
stages adversely influences crop establishment. In fact, obtaining a good stand of
plants is often the major factor which limits crop production in saline areas. The
problem of reduced seedlings establishment is also due in part to the generally
lower salt tolerance of seedling compared to established plants (Miyamoto et
al., 1985,1989). The problem is enhanced because the seeds or small seedlings are
exposed to excessive localized selinity in the seeâ bed. Pasternak (1 975), reported
that under field conditions, only 29% of alfalfa seedlings and 17% of onion
seedlings were established when using irrigation water of low salinity (1 dS/m).
These seedling percentages decrease to 24% and 14% respectively when using
saline water of 4 dS/m.
Maas and Poss (1989 ) and Maas and Grieve (1 994) indicate that wheat is
vety sensitive to salt during germination and early seedling growth. Its yield is
reduced dramatically by salt stress imposed during these stages. A water salinity
threshold value of 2.2 dS/m during the vegetative growth stage has been suggested
2.3.3 Leaching fraction
Leaching fraction (LF) can be defined as the ratio of the sum of irrigation
water applied (Di) pl us effective rain (Pe) to the total crop water requirements (ETC) :
LF = [ (Di + Pe)/ETc] -1
The value of the leaching fraction applied influences salt distribution in the
soi1 profile. Depending on the value of the LF employed, salinity profiles may be
rather uniform with depth, or they rnay be highly non-unifon, with salinities varying
from a concentration approxirnating that of the irrigation water near the soi1 surface
to many times higher at the bottom of the root zone. As a result of
evapotranspiration and drainage, the salt concentration in the soi1 profi le changes
with time between irrigations.
Bower et al. (1969) indicate that the interaction between salt concentration
of the irrigation water, irrigation frequency and leaching fraction, determines the
concentration and the distribution of soi1 salinity within the root zone. They showed
that soi1 salinity of the root zone increased sharply as the irrigation water salinity
increased and the leaching fraction decreased. Bernstein and François (1973)
report that for a given value of water salinity , crop yield decreased with the
decreasing values of the leaching fraction. This effect of leaching fraction was
enhanced by the increase of the salinity of aie irrigation water. The sarne trend was
confinned by Van Hom et al. (1993) .
The value of the leaching fraction applied has been shown to affect the
threshold value. Reporls show that the threshold value decreases sharply with a
decrease in leaching fraction (Prendergast, 1993;Bresler et al., 1982 and Hoffman
et a1.,1979). Van Hom et aL(1993) show that for a leaching fraction of 0.25 the
wheat threshold value was less than 3 dS/m.The results of Bresler et al. (1982),
showed that when the arnount of leaching fraction was higher than 0.5 a
relationship betwwn relative yieM and soi1 salinity like that descnbed by Mass and
Hoffman (19ï7) was obtained; when irrigation water supply was limited to a
leaching fraction of less than 0.5, the Mass and Hoffman mode1 was inaccurate.
Prendergast (1993), presented a linear relationship between threshold
salinity values and leaching fractions. He showed that the production function
equation between irrigation water salinity and relative yield depends on the
leaching fraction value.
In and and semi-arid areas, due to water scarcity, irrigation water is generally
applied with a low leaching fraction (in general LF is less than 0.3). In addition, in
some areas. the low natural drainability of the sub-soi1 limits the value of the
leaching fraction that could be applied (Beecher, 1991). This could be due to an the
increase of clay percentage with depth or to the existence of a clay horizon in the
lower part of the soi1 profile.
2.3.4 irrigation interval
The common recomnendation for coping with saline soils and saline waters
is to increase imgation frequency. Little evidence exists, however to support this
recommendation ( Ayers and Westcott, 1 976).
As the soi1 dries between irrigations as a result of evapo-transpiration (ET),
both the matric potential and the osmotic potential decrease. The rate at which
these processes occur depends upon the rate of (ET) and the relationship between
the matric potential (yr) and the soi1 water content (8). The rate of soi1 drying
decreases. however, as the osmotic potential decreases, thereby causing a higher
value of rnatric potential at the next irrigation. As a consequence the water uptake
by crops is reduced and hence, crop yield is expected to suffer.
Therefore, it is usually considered that irrigation of saline soils should be
more frequent because it reduces the cumulative effect of both matric and osmotic
potentials between irrigation cycles. However such an opinion is still controversial
as srnall imgation intervals subsequently induce more wetting of the top soi1 layers
and thus more losses by ET and more salt accumulation in the shallow soi1 layers.
This process has been shown by van Schilfgaarde et al. (1974) from model
calculations and experimentally by Bernstein and François (1 973). Their findings
indicate that increased irrigation frequency results in an upward shift of the peak in
the salt distribution profile thereby increasing the mean salt concentration in the
upper portion of the root zone. Furthemore, irrigating more frequently increases
soi1 evaporation, leading to additional water applications and an increase in the
arnount of the total sait applied. Consequently, shortening the irrigation interval to
overcome the salt concentrating effect of soi1 drying may result in an overall
increase in soi1 salinity.
On the other hand. extended irrigation intervals usually result in deeper
roots and larger extraction of water frorn a larger soi1 zone, resulting in a better
salinity distribution in the soi1 profile (Minhas, 1996).
The bulk of evidence in the literature shows either no advantage to
increasing irrigation frequency when irrigating with saline water ( Shalhevet et
a1 .,W83; Hoffman et a1.J 983; Bernstein and François, 1973 b;) or increased
damage ( Wagnet et al., 1980; Ayoub, 1977; Goldberg and Shmueli, 1971).
2.3.5 Soil texture
Soil propetties, mainly texture and structure, in addition to the drainability
characteristics of the soi1 profile, play a role in altering crop salinity response
through their influence on the infiltration capacity and water holding capacity.
The water holding capacity of a soi1 depends upon soi1 texture and structure.
It increases as a soi1 becornes heavier; the water holding capacity of a sandy sail
is lower than that of a medium textured soil, which in tum is lower than a fine
textured soil.
Infiltration capacity and intemal drainage properties have opposing effects
on soi1 solution concentrations. Both may decrease as the clay proportion increases
in a soil. Bhumbla (1976) and Wakil (1993) report that lack of intemal drainage
resulted in rapid salinity build-up in a clay soi1 even with the use of low salinity
water. Singh and Bhumbla (1968) indicate that accumulation of sait in the soi1
profile depends upon the clay content of the soil, and increases as the soi1 clay
content increases. They found. in fields irrigated with saline water for a period of 5 - 20 yeas in Hissar, India, that soi1 salinity was less than half of the imgation water
salinity in light texhmd soils (1 0 % clay), but, more than 1.5 times that of irrigation
water,in soils with more than (20%clay).
Under the same climatic and irrigation water management conditions, crop
response to salinity is largely affected by soi1 characteristics (Meiri, 1990). Reports
on the effect of soi1 texture on the toletance of wheat to water salinity are
inconsistent. Amimelech and Eden's (1 970) results indicate that wheat is more
tolerant for water salinity in clay soils than in sandy loam soils. Shahlavet (1 994)
argue that due to the lower water holding capacity of medium textured soils
compared to fine textured soils (clay), for the same evapotranspiration rate, sandy
soi1 will loose propoitionately more water than a clay soil, resulting in a more rapid
increase of soi1 solution concentration and hence more damage to the crops. Van
Hom's (1991) laboratory study indicates that wheat seedling emergence and
developrnent in sandy soi1 is higher than in a clay soil. Reports in the literature
indicate that other cmps are more sensitive to salinity in medium textures soils than
in fine textures soils. In a laboratory study, Kateji et al. (1994) indicate that
sunfiower and maize development dunng seedling growth are more affected by
water salinity in sandy loam than in clay loam soils. Pasternak and De Malach
(1 995) showed that tornato yields (initially planted in field plots under non saline
conditions) in sandy soils are lower than in loarny soils.
These results contradict findings of field studies conducted in lndia which
indicate that wheat is mare tolerant to water salinity in light textured soils than in
heavy textured soils (Abrol, 1990; Pal and Tripathi, 1979; Bhumbla, 1976; and
Vemia, 1973).
2.3.6 Climatic conditions
Aerîal temperature, atmosphere humidity and rainfall significantly influence
crop sait tolerance. In general most crops are more sensitive to salinity under hot.
dry conditions than under cool, humid ones (Hofmian and Rawlins,l971). High
temperatures increase the stress level to which a crop is exposed, either because
of increased transpiration rate or because of the effect of temperature on the
biochemicaî transformations taking place in the leaf. The increase in the stress level
results in changes in the salinity response function.
High temperatures reduce salt tolerance of crops (Ahi and Power, 1938).
(Minhas, 1996) reports that wheat in the cool region of northem lndia (Agra) had
higher salt tolerance (EC, of 3.8 dS/m) than in the southem warm regions
(Dhamard) where ECe was found to be equal to 0.9 dS/m. Research by Pasternak
and De Ralach (1 995) showed that under Meditenanean climatic conditions yield
of tomato planted in spring (t = 17") was around two times higher than tomato
planted in summer (t = 30') when using the same imgation water of 6.2 dS/m.
High atmspheric humidity alone tends to increase salt tolerance of some
crops by decreasing crop stress levels. thus reducing salt damage (Hoffman et
a1 ., 1 971 ). Salt-sensitive crops benefit more from high humidity than salt tolerant
crops (Hoffman and Jobs, 1983).
Rainfall has no direct effect on the salinity response, except that high rainfall
may increase leaching and reduce soi1 salt concentration, thus permitting the use
of water of higher salinity than otheWse would be possible. Dhir (1 977). reported
that in areas receiving rnonsoon rains in India, wheat has been irrigated using
saline water of 8 dS/m without yield reduction.
2.3.7 Irrigation method
The soi1 salinity profile that develops as water is transpired or evaporated
depends in part, on the water distribution pattern inherent with the irrigation method
used, in addition to hydrological soi1 properties and irrigation management.
In flood-basin and funow-basin irrigation systems (traditional system used
in Syria) the water content profile that is developed in the soi1 profile dunng
infiltration is cornpletely saturated ( Philip, 1957). In the sprinkler imgation method,
as the sprinkler intensity (1) of water application is less than the soi1 infiltration
capacity at saturation (Ic Ks) a non-saturated unifon water content profile is
usually developed in the soi1 ( Rubin and Steinhardt, 1964). The soi1 water content
in this case does not reach saturation at any point but approaches a limiting value
which depends on the sprinkier intensity. Therefore, the sait accumulated in the soi1
profile in the sprinkler system is less than the salt accumulated in the surface
irrigation systerns (Bernstein and François, 1973 a) leading to higher crop yields.
However, standard sprinkler irrigation is unavoidably accompanied by wetting of
crop foliage. Because salt can be absorbed directly into the leaves, sorne crops
(mainly vegetables, orchard crops, cotton) experience foliar injury and yield
reductions that rnay occur when they are sprinkler imgated with saline water( Maas
et a1.J 982). Sprinkler irrigation can be safely used for other crops such as wheat
and barley (Aggarwal and Khanna. 1983).
Drip irrigation systems have the advantage that high soi1 water content can
be maintained in the root zone by frequent but small water applicatons. Plant roots
tend to proliferate in the leached zone of high salt water content near the water
sources. So the typical pattern of salt distribution is minimum salt concentration
under the drippers due to leaching and a marked accumulation of salts at the
wetting front and the soi1 surface between drippers ( Shalhevet et al., 1983). Also
drip irrigation avoids foliar damage. A cornparison of drip and sprinkler irrigation on
potatoes showed a lower threshold salinity with sprinkler irrigation (Meiri and Plaut,
1 985).
2.4 Summary
In and and semi-and areas, due to fresh water scarcity and growing water
demands, water of low quality is increasingly used; including saline aquifers and
reuse of drainage water. Different strategies have been developed for the safe use
of saline water, rnainly mixing saline and non-saline water after plant establishment,
using saline and non-saline water sequentally over the growing season, introducing
supplemental irrigation with saline water in areas of high seasonal rainfall, applying
agiicultural rotations with crops of different salinity tolerances, managing irrigation,
including irrigation frequency and amount, rnanaging soi1 including tillage and
fertilizer application. The application of one or more of these strategies necessitates
accurate definition of crop salt tolerance parameters.
Available reports from a variety of agroçlirnatic regions in the world,indicate
that crop salinity response is greatiy influenced by prevailing local factors including
field practices and conditions.These factors differ widely among agricultural
regions. ConsequenHy, the salt tolerance parameters reported by the conventional
guidelines cannot be considered as ' universal".
Therefore, it is of primary importance to establish locally specific criteria
when defining suitable strategies for saline irrigation water use. These criteria have .
to take into consideration local irrigation and agricultural practices (including
irrigation method and timing, practical leaching fraction values and fertlizer use),
and in-situ field conditons including soi1 texture and structure, as well as the local
cfimatic conditions.
3. MATERIALS AND METHOOS
3.1 Site description
3.1.1 Site locations
The study areas are located in three regions in Syria where saline aquifers
are intensively used for irrigation,( Figure 3.1). These regions are:
- The low valley plains of the Khabur River Basin,
- The southem plains of the Aleppo Basin, and
- The plateau plains of the Khabur River Basin ( Shedadeh area) .
All three of these areas are located in the semi-and region of northem Syria.
3.1.2 Climate
A Mediterranean clirnate prevails in'the semi-and regions of Syria. This
climat8 is characterized by a hurnid rainy winter and a dry hot summer, separated
by two short transitional seasons.
The rainy season in this region lasts between 5 and 6 months. It generally
starts in mid October, reaches its maximum precipitation in December and January
and ends in late April. The mean annual rainfalls in the low valley plains of Khabur
basin, the Shedadeh area and the south plains of Aleppo basin are 275, 195 and
262 mm, respectively.
The monthly mean daily temperature in the region is maximum value
in August ( 3S°C), decreases to around (22°C) in October, reaches its minimum
value of (7°C) in December-January and nses back up to (25°C) in June.
As established by a US Class A evaporation pan (set-up within an irrigated
field), mean annual potential evaporation was 2230 mm in the low plains of Khabur
basin. 2450 mm in the Shedadeh area and 2580 mm in the south Aleppo basin.
Tables ( 3 - la and 3-1 4 ) present the main climatic characteristics recorded
at the Hassakeh rneteorological station which is located in the center of the Khabur
Basin and at the Boueider meteorological station which is the nearest
meteorological station to the study area of the southern Aleppo basin.
3.1.3 Soil characteristics
a) Soil textum
Soils at the three locations differ widely in their texture. Typical soi1 texture
profile for the three locations are shown in Figure 3.2, (data are in appendix A,
Table A-1 ).
Soils in the low plains of the Khabur valley are predominantly clay. The clay
proportion increases with depth and may reach, at a depth of one meter, more than
60%. This limits the soils in ternis of intemal drainage, thereby restricting the
arnount of irrigation water that can be infiltrated and the degree of natural leaching
which can take place during the rainy season.
The soils of the southern Aleppo Basin are clay loarn. The soi1 structure is
generally subangular blocky in the surface horizon and prismatic below. Sail
KHABUR VALLEY PLAINS ALEPPO SOUTHERN PLAINS
PERCENTAGE OF SOK PARTIWLES (%) PERCENTAGE ûF SOlL PARTICULES 1%)
SHEQADEHAREA
PERCENTAGE OF SOlL PARTICULES (%)
aggregates contain many fine pores allowing for rapid infiltration.
In the Shedadeh area, the soils are predominantly loarn. The sand portion
generally increases with depth and may reach more than 50% at a depth of one
meter. This improves the soi1 drainability.
b) Physical characteristics
The water retention characteristics of the soils at two sites in each of the
three regions are presented in Figures (3.3 a, b and c).
Soils in the low plains of the Khabur valley have a high water content at
saturation (es) and high water holding capacity (hc). The average value of (es) and
(hc) for a soi1 profile of 120 cm depth are 0.55 cm3/g and 0.28 cmlcm, respectively
(Table A-2 in Appendix A). These characteristics along with the increasing clay
percentage with depth (which limits deep water infiltration), increase the amount of
irrigation water which can be lost by evapotranspiration from the soi1 profile.
In the plains of the southem Aleppo basin, the average value of both
water content at saturation ( 8,) and water holding capacity (hc) for the whole soi1
profile are 0.45 cm3/g and 0.24 crn/cm of soi1 depth, respectively. Therefore,
compatatively to low plains of the Khabur valley, soils in the Aleppo basin have
better drainability
In the Shadadeh area, the average value of (8,) and (hc) are
0.3?cm3/g and 0.2 cmlcm of soi1 depth, respectively. The low values of these two
parameters along with the increasing sand percentage with depth allow for good
ABOU-ARZALA OUM-HAJRA
+, DEPTH (80-100)cm . . . A
:. . . . S . . . . . . . . . . .
O 10 20 30 40 50 60
WATER CONTENT (%, WEIGHT)
1600 I I 1
t : OEPTH (O'2O)CM
1400 . . - - - - . 1 .- +DEPTH (100-l2O)CM . h s * 1 9
. . . . . . . . . . . . . . . . =1200, : : 1 .:. .:. .:. P . 1 ,
. . . . . . a . . . . . . . . . . . 3 ,000 : , .; .: .:. E Z
* l a
. . . . . . . . . . . . . . . . . . ~ . . . . . 0 800 , 4 .I
t; ; 1 :
. . . . . . . . . . . . . . 1 - . . . . . 2 600 : .,.: .: .: 2 '
1 : . . . . . . . 400 : . . . : . . . i . . . . . . : . . . . : a s 200 . . . . . . .
0. 1
O 10 20 30 40 50 60
WATER CONTENT (16, WEIQHT)
KHANASSER
1 - Depth (O-2O)cm
1400. . . . . . . . . .i. . *-depth (BO-100)cm h
3 . I . =1200 . . . ; . . . .: . i . .:. . . . . , . . . . . . . . . . O S I *
: i : . . . . . . . . . . . 31000 . . . ; , . . . . .;. . . ; . E z ' 1 . . . . . . - . . . . . : . . . : . . . . . 9 8 0 0 . . : .i- ç. O I -
. . . . . . . . . . . . . . . . . . . . . . . . 2 600 : 1 . : ' ; 2 1 . : .,. .:. . . . . . . . . . . : . . . . . . . . . .
200 . . . ; . . .
O l
O 10 20 30 40 50 60 WATER CONTENT (%, WEIGHT)
AL-RAHEB
1600 *
t - DEPTH (O-2O)cm
1400, . . . . . . . . ,. +' DEPTH (100-120)cm h
2 : i : . . . . . . . . . . . . . . . . . = 1200. ; ; I : .; .: .~
n * l a u . . . . . . . . . 1 1 :
. . . . : " ' : g 1000~ ' . v - : Z . I .
. . . . . . . . . . . . . C "O0 - i - , 1 . : . O 1 .
. . . . . . . . 2 600 : . . , . ? . : . . . : . . . : : 1 : 2 ' 1 . . . . . . . . . . . . . . . . : . . . . f 400 : : .,. i
B 200. . . . * . . .
O 1
O 10 20 30 40 50 60
WATER CONTENT (Y', WEIGHT)
OUM-HAJARA -1 OUM-HAJARA -2
O 10 20 30 40 50 60
WATER CONTENT (%, WEIGHT)
1600, I i - OEPTH (O-2O)CM
- . - . . +. DEPTH ( 8 0 - 9 0 ) C M h
2 =1200.. . . & 1. ! . . . . . . . . . . . . . . . . . . . . . . n + C
. . . . . . . . . . . . . . . . I : d . .:. .:. .:. 4
O 10 20 30 40 50 60 WATER CONTENT (%, WEIGHT)
drainabilty of the soi1 profile. Under these conditions, less irrigation water is
expected to be lost through the soi1 profile by evapotranspiration cornparatively to
the other two locations, and more water can percolate below the root zone.
3.1.4 Saline aquifers
Saline aquifers are the only water source for irrigation in the three regions.
Artesian aquifers ( confined aquifer) are the main aquifers which are exploited for
irrigation. The depths of these aquifers Vary between 180 - 240 m and their well
productivity varies between 30 m3/hr to 60 m3/hr. In some areas, unconfined
aquifers are exploited. The depth of these aquifers are usually less than 50 m and
are of lower productivity (20 m3Brto 30 m3/hr). Water salinity in each region differs
among farm locations. It varies as follows:
- in the low plains of the Khabur valley and the south plainsof Aleppo well
water salinity varies between 0.4 dSlm and 14 dSlm;
- in the Shedadeh area, well water salinity ranges between 5 dS/m and 7
dSIm.
Water quality of some representative wells in the three regions are presented in
Table (3 -2).
3.1.5 Agricultural practices
In al1 three regions wheat is the major irrigated crop. It is grown on about
80% of the irrigated acreage (Waki1.1993). Wheat is wuaily planted in late October
and harvested around rnid June. Various local varieties of both bread and durum
wheat are grown, the varieties most widely planteci are Sham 3 and Djezireh (durum
wheat) and Sham 4 (bread wheat). Seeding rates range between 250 kgha and
300 kgha. In general, crop rotation is limited to wheat.
Fertilizer application is a common practice in the study areas.
Table@-2) Gioundwater quality a n a m tiom sonm wells in the three regions.
. Fann name
r
Khabur low plains
Bougha (1)
Bougha (3)
Dabagieh
Bougha (3)
Abou Arzala
Smei han G harbie
Oum-Houjei ra
Thamad (2)
Thamad (1)
Aleppo south plains
Tel-Toukan I
Om-Gharraf (3)
Om-Gharraf (4)
Tel-Aran r
Tawahinieh
Ourn-Hota
Hawaweieh
Khanasser
Kourbatieh (fami 2)
Shadadeh area
Oum-Hajra (farm 1 )
Oum-Hajra (farm 2)
Al-Siha
EC
( d s m
1.62
2.09
2.95
2.90
5.05
7.16
11.16
2.01
1.2
1.47
2.95
3.21
4.95
4.0
6.4
7.6
1 1.55
14.1
6.5 1
7.41
6.50
Na
(mq/')
5.7
7.8
3.7
1 1.4
18.0
42.1
83.4
4.0
4.4
7.8
27.0
23.3
17.0
20.0
38.8
38.8
61 .O
74.0
36.5
45.0
37
Ca+Mg
(n=qn)
6.98
16.3
37.7
35.1
41.9
55.5
65.9
20.57
16.42
10.1
2.2
24.2
41.1
26.6
43.5
53.6
58.9
97.1
48.59
58.25
45.50
SAR
3.05
2.74
0.85
2.72
3.93
7.99
14.62
1.24
1 2 4
3.47
5.28
6.71
3.75
5.49
8.33
7.49
1 1.23
10.62
7.4 1
7.57
7.43
Boron
( P P ~ )
0.28
0.57
0 .46
0.62
1.47
1.25
2.45
0:18
0.23
0.52
0.65
0.82
1 .O1
1.57
1.25
1.95
2.2
2.65
1.20
1.35
1.25
PH
7.6
7.3
7.5
7.4
7.5
7.5
7.2
7.4
7.3
7.6
7.1
7.4
7.3
7.4
7.5
7.2
7.3
7.6
7.4
7.5
7.5
Phosphate ( P , O5 ) is applied at sowing at an average rate of 150 kgha. Nitrate
(N) is applied in two doses of around 80 kgha each. The first application after
sowing and the remainder during early spring tillering.
3.1.6 Irrigation methods
Traditional furrow-basin irrigation is comrnonly used in the thiee regions.
This method consists of dividing the fam irrigated area into small "furrowed" plots
of 50 m2 to 100 m2 depending on land slope. The plots are bounded with earth
ridges of 0.5 m height. For each irrigation application the plot is flooded to a depth
of around 0.1 m height.
The number of irrigation applications and their amount and timing are
govemed by rainfall pattern and by local well yield. In general, wheat receives three
to six irrigations, of which the first occun immediately after planting. The remaining
irrigations are usually given between the beginning of April and the end of May.
The imgated areas in the three regions are not provided with either surface
or subsurface drainage networks.
3.1.7 Wheat irrigation water requimment
Irrigation water requirements for wheat in the low plains of the Khabur valley
and the south Aleppo plains were estimated using the modified Blaney-Criddle
method developed by Doorenbos and Pluitt (1977). The following equation was
applied for the estimation of wheat evapotranspiration (ETC):
ETc = K, ETo
where: K, is a crop coefficient which varies with crop growth stage;
FT, represents "reference crop evapot raspi rationn.
The rnonthly distribution of rainfall (P) and wheat water requirements ( ET,)
in the two regions, indicate the need for irrigation application in two separates
periods during the wheat growing season (Figure 3.4. 3.5). During these periods
wheat evapotranspiration is higher than rainfall (ET, > P). The first period occurs
after planting, it coincides with the germination and seedling growth stages of
wheat. The second pend extends between February and June, and coincides with
the flowering and grain filling stages.
3.2 Farm selection
Special criteria were developed for selectian of the fams from which to
collect data. These criteria included elements related to irrigation history and,
current imgation and agricultural practices. All the select4 farms were applying the
following practices:
- the wheat variety grown was durum (mainly Sham 3)
- the applied seeding rate was between 250 kgha to 300 kgha ;
- al1 the selected fams had been using saline irrigation water for more than
three years. The end of this three year period (under normal rainfall
conditions and without large seasonal variation), the soi1 salinity profile can
be expected to reach an equilibrium condition. Beecher (1 991), Maas et al.
160 Rain
Oct Nov Dec Jan Feb Mar Apr May Jun
I I Figure 3.4 Monthly distribution of rainfall (P) and wheat requirements (ETc) in the low plains of Khabur basin
(1 988) and Mehanni and Repsys (1 986) al1 found that aie upper soi1 profile attained
an equilibrium after three yean of irrigation with saline water.
- sowing into a dry bed was a common practice in the selected farms.
- the number of irrigation applications practiced on these fams varied
between four and five applications, including the first after sowing. The
remaining irrigations were applied between the beginning of April and the
end of May or into June, as indicated in Figures 3.4 and 3.5.
- the total amount of irrigation water applied during the growing season
varied between 320 mm and 400 mm.
- al1 the farms have an area varying between 5 and 10 ha
3.3 The general approach
In order to define the " in-field " wheat yield production function with regard
to irrigation water salinity and the threshold irrigation water salinity value in the
three regions, a field survey covering 32 farms in the low plains of the Khabur
valley, 30 fans in the southem Aleppo plains and 12 farms in the Khabur plateau
plains (Shedadeh area) was conducted for two growing seasons: 1993/1994 and
19941 995. These f a m were using groundwater of different degrees of salinity and
were applying similar cultural and irrigation practices as described in section 3.2.
The field survey aimed to collect data on fam well water salinity "EC;,
wheat productivity (Y), and soi1 salinity. A total of 74 fams were sampled.
AU74 f a m were sampled for water salinity (ECJ and yield. but due to economic
limitations only 29 famis in the second year were sampled for soi1 salinity (ECJ for
a control, an additional five fams practiced rainfed agriculture were sampled.
In order to eliminate the effect of seasonal climatic variation on wheat
productivity, the relative wheat yield Y: of each fam was then determined by
dividing the farm's wheat yield by the average yield of five famis in the some reg ion
irngating with non-saline water (having an EC less than 0.7 dç/m). The two
parameters, relative yield "Y," and irrigation water salinity EC,, were correlated to
obtain wheat yield response functions to irrigation water salinity for each location
and hence to define graphically the corresponding threshold water salinity value.
This Yield approach" for defining the 'in-fieldu crop yield response function
to irrigation water salinity and consequently crop sa1 tolerance threshold values
has been used by various researchers (AICRP, 1994; Oosterbaan et al., 1991 ;
Abrol, 1990; Abdel Dayem et al., 1989; Nijland and El-Guindi, 1984; and Bhurnbla,
1976). This appmach has the advantage of better reflecting to the local
environment and to the real field conditions than the experimental methods applied
in different conventional crop salt tolerance studies. These experiments were
executed either in small lysirneters (which are constituted of an artificial soi1 media)
in a greenhouse environment (Kate ji et al., 1994, van Hom et al., 1993; van Hom,
1991, Maas and Gtieve, 1990 ) or in small field plots artificially salinised (Francois
et al., 1994; Beecher 1994; François et a1.J 986; Maas and HoffmanJ Sn; Ayers
et al., 1 952). Therefore the results obtained f rom the" field approach ' method are
more representative of the field conditions.
In addition, the graphieal methoci for defining crop threshold salinity value is
the only method commonly used for studying crop salt tolerance (Maas and
Hoffman, 1 977; François et al., 1 986 ) .
3.4 Data collection
3.4.1 WeII water salinity
Well water was collected from al1 74 f a m for (ECJ analysis. In addition,
well water from 21 f a m were collected for chernical analysis which included EC,
pH, Ca, Na, Mg and Boron (Table 3-2). using the methods of US salinity laboratory
(Richards, 1 954).
3.4.2 Whrat yield
Average wheat (grain) productivity was obtained by monitoring the number
of 125 kg 'bag' of dry grain received per unl area of the farm for the two agricultural
seasons was detenined by dividing total wheat production of the fam by the
cultivated area.
In addition, relative yield ( Y, ) of each farm was detennined as indicated in section
(3-3).
Appendix A, Table (A-1) presents the value of wheat productivity in five
farms in Khabur basin and Aleppo south plains using non-saline water, in addition
to well water salinity, wheat productivity and wheat relative yield in the studied
farms for the two growing seasons 1993/1994 and 1994/1996.
3.4.3 Soil samples
At harvest time (JuneJuly) of the second year soi1 samples were collected
from fourteen f a m from the Khabur low plains, twelve farrns from Afeppo south
plains and three f a m from the Shedadeh area. Two representative sarnpling sites
were selected at each farm, in a central flat area of the field. Soil samples were
obtained (using auger) at 20 cm intervals to a depth of 120cm. Samples were
analyzed for physical properties and for electrical conductivity of the saturation
extract (ECJ using the method of the US Salinity Laboratory (Richards, 1954), (see
Appendix C).
4 . RESULTS AND DISCUSSION
4.1 Statistical analysis
The "One Way Classification Methodw was chosen to study the effect of soi1
type and irrigation water salinity on wheat yield. In applying this method, soi1 type
(sandy, clay, clay loam) was considered as a class, EC, as the independent
variable and relative yield as the dependent variable. The cornputer "Statistical
Analysis Systemn (SAS) was used to analyse the data obtained dunng the two
growing seasons of 1993/1994 and 1994/1995. The results are presented in the
Tables (4-1) and (4-2).
The results of the statistical analysis show that, as expected, both EC, and
soi1 type have a significant effect on wheat yield (k0.01).
In order to evaluate the effect of soi1 type (clay soi1 and clay loam) on yield,
the statistical analysis was performed on yield data obtained from sites with an EC,
less than 4 dS/m, which represents the water salinity threshold value as reported
by the universal guidelines. This limitation was applied in order to evaluate the
effect of soi1 type on yield within the limit of the "universal salt tolerancen and to
eliminate any interference in the obtained data which may result from the use of
high water salinity. The results of this analysis show a significant effect of soi1 type
for the year 1993/1994 of (Pc0.01) and for the year 1994/1995 of (Pc0.08).
In addition, the results of the statistical analysis for the clay soi1 and loarn soi1
show significant effect of soif type on yield (Pe0.01). Simlar results were obtained
for the clay loam soi1 and loam soi1 (Pq0.05).
Table (4-1) Results of statistical analyrb for the year 1993/1994
Source P r>F 1 Result
Soil r
ECw
0.0014
loam versus clay
Clay versus clay loam 1 0.01 1 significant 1
significant I
0.0001
0.0003 1 significant
loam versus clay loam
Table (4-2) Results of statistical analysis for the year 1994/1995
significant
1 Source I P ~ > F TReiGt 1
0.01 39 significant
loam versus clay 1 0.0001 1 significant r 1
Soil
ECw
1 Clay versus clay loam 1 0.08 1 Not significant 1
0.0001
0.0001
loam versus clay loam L
4.2 Salinity thieshold values
Figures 4.1,4.2. and 4.3 illustrate the relation between relative wheat yield
and irrigation water salinity for the selected farrns in the three regions. They
indicate that the relationship between the two parameters is somewhat scattered
(Table B-1 to 8-7 in Appendix B). This data scatter is postulated to be caused by
diff erences
significant
significant
0.0002 significant
in agricultural inputs and irrigation management practices between famers,
including land preparation, sowing date, irrigation timing and application depth,
fertilizer application and management of various agricultural field works. This data
scatter is a common feature of sirnilar studies (Oosterban et al., 1991 ; Abdel Dayem
et al. 1989; Nijland and El-Guindy, 1 984).
The envelope curves in each figure represent the maximum and minimum
yield. The upper cuwe defines the maximum threshold water salinity value EC,
(point 'Y" on each figure). EC, for each region is:
- 1.2 dSlm for the low plains of the Khabur (clay soils)
- 3.5 dS/m for the south plains of the Aleppo basin (clay loam to loam soils)
- 6.5 dS/m for the Shedadeh area ( barn to sandy loam soil)
These values are very close to what were obtained in a field study for wheat
conducted in India: 1 .O dS/m for silty clay loam, 4.0 dS/m for sandy loam and 6
d S h for loarny sand (AICRP, 1994). In Tunisia, a Mediterranean country, van Hom
(1991) and van? Leven and Haddad (1968) reported that threshold water salinity
values averaged 1.8 dSlm for clay soils and 3.5 dSlm for loamy soils.
For an irrigation water salinity value higher than the threshold value
(EC>ECJ, wheat yield along the upper envelope cuwe (Figures 4.1 , 4.2, and 4.3)
decreases sharply in an 'hyperbolicn form which indicates that under practical field
conditions, the production function (relationship between yield and irrigation water
salinity) is not linear as indicated in th8 Universal guidelines source (Figure 2-1)
and in the Maas and Hoffman model (1977 ). The pattern of yield response
functions to water salinity for different crops ( pasture, luceme, tomato) obtained by
Prendergast(l993) in Sheparton, Australia,ere similar to the results presented in
Figures 4.1,4.2 and 4.3.
4.3 Aiuilysis of recrults
Analysis of the irrigation water threshold values obtained in our research
work has led to the following conclusions:
a) there is a difference between water salinity limits EC, (threshold value)
for the three regions (see statistical analysis in section 4.1).
Since famlng practices are similar for the three regions, this difference may
be attributed to factors related to the difference in soi1 texture and structure. These
factors affect soi1 infiltration capacity and water retention, and hence salt
accumulation in the soi1 profile.
b) the obtained threshold values are substantially different from the universal
irrigation water salinity limit (threshold value) of 4 dS/m reported in the
literature by Maas (1 990) and Ayers and Westcot (1 985).
This may be due, in addition to the physical soi1 characteristics effects, to the
difference in the agriculhiral and imgation management conditions between the real
practices applied in the field and the artificial salinized experimental
plots.Differences in the latter expenments may include planting under non saline
conditions (saline seed bed and using saline water during eariy growth stages),
inigating frequently and applying high leaching fraction in addition to other factors
such as climate and soi1 texture.
4.31 Effect of soi1 texturct and structure on irrigation watcr salinity
threshold value.
Differences in soi1 texture and structure between the three regions affected
the rate of salt accumulation in the soi1 profile. which results from the
repeated annual application of saline imgation water.
the level of seedbed salinity present at sowing time (resulting from previous
irrigation seasons)
the extent of "natural leachingn of the soi1 profile which can be acheived
during the rainy season (October to April).
All of these factors affect wheat salt tolerance to irrigation water salinity and
hence the irrigation water salinity threshold value of the crop as is discussed below.
4.3.1.1 Development of salinity profiles in the three locations.
a. Soil salinity development
Figures (4.4 a to 4.4 h ); (4.5 a to 4.5 g) and (4.6 a and 4-6 b) present the
soi1 salinity profiles at the end of the irrigation season for various farms in the low
plains of the Khabur valley, the south plains of Aleppo basin and the Shedadeh
areas respecüvely, resulting from the use of saline water wells of different salinity.
Figures ( 4 4 , (4.5a) and.(4.6a) present the soi1 salinity profile at fans practicing
rainfed faming only, for each of the three regions (yield data are presented in
Appendix C,
HALELIEH, ECw 1.15 dS/m NASSERIEH-3, ECw 1.1 9 dSlm
I
Figure (4.4 c) Soil salinity profile in two sites (a,.) at the Halelieh and Nasserieh-3 farrns, low plains of the Khabur basin
THAMAD-2, ECw 1.2 dS/m BOUGHA-1, ECw 1.62 dSlm
TWAHINIEH, RAlNFED ESLAMIN, RAlNFED
I
Figure (4.5 a) Soil salinity profile in two sites (.,A) at the Twahinieh and Eslamin farms for rainfed conditions, south plains of Aleppo basin
Table (C-1, C-2 and C-3).The above figures show:
in each location ,the amount of salt accumulated in the soi1 profile
increases with increasing salinity of irrigation water. Similar trends in soi1 salinity
development have been obsenred in field experiments (Shanna et al. (1 991), Maas
et a1.(1988), and Hoffmann(l988).
for the sarne irrigation water salinity, large differences in the amount of salt
accumulated in the root zone exists between the three major regions. Salinity
profiles in the low plains of the Khabur basin (clay soil) have attained higher values
compared to the south plains of Aleppo Basin (clay loarny soil) which in tum are
higher than the Shedadeh region (loam to sandy loam).
These results clearly indicate that the level of salt accumulation in the soi1 profile
is a function of the soi1 clay content, increasing with the increasing clay percentage
in the soil. Clay percentage average 56%, 40% and 24% in the low plainsof the
Khabur valley, the south plains of Aleppo and the Shedadeh areas respectively.
This observation is in agreement with findings which indicate that salt accumulation
in soi1 profiles increase with increasing clay soi1 content AICRP,1994; Singh and
Bhumbla (1968); Singh and Kanwar (1 963).
The above results can be explained by the fact that an increase in clay
percentage will likely reduce the infiltration rate of a soi1 and increase its water
retention capability (in Figures 3.3 a, 3.3 b, and 3.3 c). Therefore, for a given
amount of irrigation application, the amount of irrigation water that can percolate
below the root zone is reduced. This situation leads to saline water greater
retention of which when exposed to evapotranspiration processes in the root zone,
results in more salt accumulation. In lighter textured soils, the amount of irrigation
water that percolates below the root zone is generally higher compared to a fine
textured soil. As a result, less water is retained in the root zone, leading to less salt
accumulation.
The average soi1 salinity (EC,) accumulated in the upper soi1 profile (0-80)
cm and the salinity of the irrigation water (EC,) in the low plains of the Khabur
valley and southem Aleppo plains are presented in the Table (4-3) and Figure (4.7).
Two main observations can be made from this figure:
a) th8re is no significant difference in the soi1 salt levels between rainfed
famis and f a m using irrigation water of less than 0.7 dS/m. This indicates that the
leaching fraction usually applied in the area (average 0.20) in addition to the annual
rainfall are sufficient for maintaining a soil salt balance when using EC,<0.7 dS/m.
Salts start to accumulate in the soi1 profile when the salinity of the irrigation water
exceeds 0.7 dS/rn. This observation is in accordance with the water quality criteria
suggested by the University of California Cornmittee of Consultants (1 974).
b) for the same value of irrigation water salinity, the amount of salt
accumulated in the root zone is higher in the Khabur valley low plains(clay soi1 )
than in Aleppo south plains( Clay loam to loam soi1 ). These results are in
accordance with the findings of Meiri (1 990) and Bhumbla (1 976).
Therefore, for the same level of irrigation water salinity, the crop is grown in
a more saline media when planted in a fine tetured soi1 (clay soil) than in a light
EC of the irrigation water (dS/m)
Figure 4.7 Relationship between average EC, of th soi1 upper layer (O-8Ocm) with the EC, of the irrigation water in the low plains of the Khabur basin (clay) and the south plains of Aleppo basin (clay loam/loam)
textureci soi1 (loam or loamy sand soil). This means that crops grown in saline fine
textured soils, generally face more sa1 stress (osrnotic potential). A crop growth
reduction can be expected primariy; because the higher osmotic pressure present
increases the energy that must be expended by the crop to acquire water from the
soi1 of the mot zone and to make the biochemical adjustments necessary to survive
under stress; this energy is diverted from the processes which lead to growth and
yield ( Rhoades, 1990). This fact explains the field results obtained in Our research
and similar results found in other agroclimatic regions of the world (AICRPJ994;
van Hom, 1991 ; Bhurnbla, 1976 and van? Leven and Haddad, 1 968) conceming the
higher yield reduction of wheat grown in saline fine textured soils than light telured
soils.
Table (4-3), Irrigation watei salinity (EC,) and average soi1 salinity ( EC,) of 0-80 cm in the studied ferma
Aleppo south plains ( Shedadeh area
Farm name
Twahinieh (') 1 Smehan Gh. (*)
- 0.35 Om-Hajara (2) 6.50 2.80 Nasserieh (*)
Nasserieh 7
Nasserieh 12
Eslamin (*)
0.43 0.37 Om-Hajara (1) 6.51 3.00 .-
Al-Sharaf
1 Nasserieh (2) Tel-Tokan
Om Jerin
Thamad (2)
Bougha (1)
Om Garraph (1)
Om Garraph (2)
Om Garraph
( Bougha (3) Tel Aran
b. Regiblrion analysis
In order to evaluate the degree of association of the two dependent
parameters irrigation water salinity (EC,) and the average soi1 salinity (€Cd
accumulated in the upper soi1 profile in the low plains of the Khabur basin and
Aleppo southem plains and to establish the relation between these two variables,
a correlation and regression analysis was undertaken. The analysis aims to
determine the correlation coefficient and the regression equation function which
best describes the relation between these two variables. The regtession analysis
was applied for irrigation water salinity (EC,) values higher than 0.7 dWm (Ayers
and Westcot. 1976).
The two dependent parameters EC, and the resulting EC, are highly
conelated (in both the Khabur basin and Aleppo basin) . The following curvilinear
regression function describes the relation between ECw and EC, with high degree
of correlation:
- in southem Aleppo plains:
Y = 1.86531n(x)+0.338 with R2 = 0.9437
- in Khabur basin:
Y = 1.77731n(x)+1.243 with R2 = 0.9751
These two regression functions are illustrated in Figures 4.8.
4.3.1.2 Seed bed salinity at 8owîng t h e
Differences in the amount of initiai seed bed salinity at sowing tirne between
aie three regions is an additional factor which substantially influences wheat yield.
Due to a la& of rainfall during the summer, the salt accurnulated in the soi1 profile
from the previous irrigation season is still present for the ensuing season's wheat
crop. For the same irrigation water salinity, initial seedbed salinity in light textured
soils (Shedadeh region) is lower than in heavy textured soils (the low plains of the
Khabur valley). Soil salinity profiles at the end of the imgation season at three
farms in each of the three regions confinn this Figure 4.9 The three fams within
each region were chosen such that the well water salinity was approximately equal.
Germination and emergence are crucial to the success of cropping and the
establishment of optimal plant population density.This is a major bottleneck for
succesfuf crop production (Rhoades et a1.1992). Various reports available in the
literature indicate the importance of keeping soi1 salinity levels low during
germination and ernergence of seedlings. A saline seedbed adversily influences
crop establishment and ultimately affects its productivity (Minhas and Gupta, 1993;
Naresh et al., 1993; Beecher, 1991 ; Meirï.1990; Hamdy,1 990: Maas and Poss,
1 989; Rains et al, 1987; and Bernstein ,1974). The results of François et al. (1 994),
Minhas and Gupta,(1993) and Harndy (1 990) indicate that wheat seed germination
decreases as seedbed salinity increases. In a laboratory experiment, François et
al (1 994) found a decrease of wheat seed germination of approximately 50%for an
€Ce seedbed salinity of 8.8 dS/m.
The reâucüon of seedling establishment is due in part to the lower sait tolerance of
seedlings compared to established plants (van Hom, 1991 and Bernstein et
a1.,1955). Wheat is very sensitive to salt during germination and early seedling
growth and consequently yield is decreased dramatically by salt stress imposed
during these early growth stages Maas and Grieve(1994) and Maas and
Poss(l989) . Maas and Gneve (1994) showed a yield reducüon of around 30% for
an average seedbed salinity of 8 dSlm imposed during these growth stages.
Recent studies performed in lndia on the effect of seeding rate on wheat
yield under saline irrigation (ECw of 8 dS/m) showed 10 -15% improvernents in
wheat grain yield when fields mre seeded with 25% extra seed compared with the
conventional thinning to rnaintain the recommended for n o m l fresh water irrigation
(AICRP, 1994).
Similar results were obsewed in the Shedadeh area. For approximately the
sarne irrigation water salinity and the same cultural practices. wheat yield increases
with increasing seeding rate (Table 4-4). A 30% increase in wheat yield was
obsewed for 50% increase in seeding rate.
Tabb (44) Wheat yield for various d i n g rate, Shedadeh area
4.3.1.3 Natural leaching
Under the Meditemean climatic conditions prevailing in the three regions,
the effective part of the rainy season extends between December and the end of
February. During this period, approximately 60% of the annual rainfall occurs
(Figures 3.4 and 3.5). On aie other hand, due to relatively low temperatures, higher
relative air humidity and lower evaporation rates, (Tables 3-1 ,a and 3-l,b), the
above period is considered a dormant period for wheat growth. Evapotranspiration
rate is at his lowest value, it averages less than 0.5 mmlday during December and
January as is shown in Figures (3.4) and (3.5). Therefore, during this period, the
amount of rainfall is higher than the rate of evapotranspiraton ( P > ETC).
Farm narne
Um-Hajra, Alawi-1
Al-Siha, Ibrahim
AI-Siha, Alawi Hussein
Um-Hajra, Suleih
Um-Hajra, Suleiman
Um-Hajra, Alawi-2
Seed rate
(km@
250
300
320
320
350
470
Ecw
(dS/m)
6.50
6.75
6.50
6.18
6.5 1
6.50
Yield
(ma)
3.87
5.07
5.12
5.21
5.62
6.50
Yield / seed rate
15.5
16.9
16.0
16.3
16.1
13.8
This specific clirnatic situation, by reducing (or eliminating) the upward flux
of soi1 water, enhances the natural role of winter rainfall in achieving some leaching
of the upper layers of the soi! profile. In this case. the bulk of the rainfall infiltrates
into the soil, rnoving the salts downward. The extent of this "natural leaching" (ie.
amount of reduction in soi1 salinity in the upper the soi1 layers), depends on soi1
texture and structure as well as the actual rainfall pattern with respect to amount
and temporal distribution.
Natural leaching is more effective in coarse textured soils than in fine
textured soils. Due to their higher permeability and lower water-holding capacity,
changes in salinity in coarse texhired soils are faster than in fi ne textured soils Meiri
(1 990). Figure ( 4-10) illustrates this variation in soi1 salinity profile between the end
of oie irrigation season and the end of winter rainfall on fami in Aleppo south plains
using well water with a salinity of 14.1 dS/m. It shows a high reduction in the salinity
of the soil profile resulting from winter rainfall. Salinity reductions of similar ordrer
of magnitude have been reported by Styliano (1 970) in an area of sandy loam soils
with 150 mm of annual rainfall, in Cypnis.
Figure (4-1 1) presents the reduction of soi1 salinity on farms in the Khabur
low valley plains kept fallow since 1987 to achieve natural leaching of salts
accumulateci through saline irrigation in previous seasons (Wakil, 1993). It shows
slow reduction in soi1 salinity. This result indicates that natural leaching is less
effective in the loamy clay soi1 of the Khabur low plains, compared to the soils of the
Aleppo south plains.
In the continental monsoon clirnatic areas of India, natural leaching resulting from
monsoon rain (around 1,000 mm during the period of July to September) is more
effective in coarse textured soils than in fine soils (Minhas and Gupta1992). The
amount of rain water needed to remove 80% of the salts accumulated during the
pend preceding monsoon was approximately three times greater in fine textured
soils than in coarse soils.
Reductions in soi1 salinv which result from natural leaching by winter rainfall
have a beneficial effect on the development of the plant during the ensuing growth
stages of flowering and grain filling. Salinity stress imposed at these stages is
known to affect growth and yield components such as kernel number and weight
and can lead to a significant reduction of total grain yield ( François et al., 1994;
Maas and GrieveJ 990; Maas and Poss, 1989). The study of François et al. (1 994)
indicates an average reduction of wheat yield of 30% for an increase in soi1 salinity
from 1.4 dS/m to 10 dS/m.
4.3.1.4 Sumrnary
The above results indicate that wheat salt tolerance to water salinity is
affecteci by soi1 texture. They show that due to differences in soi1 salt build-up and
effectiveness of natural leaching which occured during the rainy season. wheat is
less sensitive to irrigation water salinity in light textured soils than in fine textured
soils. The obsenred degree of reduction of water salinity threshold values (ECJ
between the three soif types is of the sarne order of magnitude as reported in field
studies by AlCRP (1 994), Abrol(l99O) and Bhurnbla (1 976). The above concl usion
is contrary to the findings of Pasternak and De Malach (1995), Van Hom(1991),
Kateji et al. (1994). and Amimelech and Eden (1970) who undertook their works
under non saline conditions (including initial non saline seed bed and using fresh
water during sowing and eariy seedling stages), and in experimental lysimeters or
plastic tanks which f o m an artificial soi1 media of limited depth which disturbs the
continuity of downward water flow and hence affects the process and the pattern
of salt accumulation in the soi1 pofile.
4.3.2 The discrepancy between the obtained irrigation water salinity
limita and the univemal guidelines value.
Wheat (durum) salt tolerance data reported in the conventional guidelines
have been obtained from experiments conducted on field plots in a silty clay soi1
(François et al., 1986). This soi1 is of a similar texture as those of the Khabur low
valley plains. However, the value of the irrigation water salinity threshold value
obtained in our field study (1.2 d S h ) is much lower than the conventional threshold
value reported in the literature (4 dS/m). This may be attributed to the difference in
irrigation water management between actual fam practices and the experirnental
set ups used to develop the guideline.
In addition to the factors related to soi1 texture and to the specific agriclimatic
conditions prevailing in the studied amas, other factors related to on-farm irrigation
management and practices, affect wheat tolerance to irrigation water salinity:
a) use of saline irrigation water during germination and early growth stages
(in salt tolerance experirnental studies, crops are usually irrigated with fresh
water during these stages);and
b) application of a low leaching fraction and less frequent irrigation
compared to the usuai experirnental practices applied in crop salt tolerance
studies.
All of these factors contribute to create differences in management
conditions between the experimental procedures applied in the universal salt
tolerance studies and the on-fan practices of using saline water. These
management conditions affect soi1 salinity build-up and plant development.
4.3.2.1 Use of ralim water during early giowth stages
In the three regions studied, saline aquifers are the sole source of irrigation
water. Farmen in the selected f a m usually apply saline water in the various wheat
growth stages, including one after-sowing irrigation which coincides with the
germination and seedling growth stages and three irrigations dunng the period
extending from April to May. which coincides with the flowenng and grain filling
stages.
Sal tolerance of wheat varies mth growth stages (Maas and Grieve. 1994;
Francois et al. 1994; Maas and Grieve. 1990; and Maas and Poss. 1989). Results
of greenhouse expedmenh petformâ by Maas and Poss (1989) indicate that wheat
is most sensitive during the vegetative and eariy reprodutive stages, less sensitive
during flowenng and, least sensitive during the grainalling stage. The results of
these experiments cleariy indicate that the wheat poduction function in response
to ECw depends on the stage during which the saline water is applied. They showed
the existence of specific production functions for saiinity imposed during vegetative.
reproductive and maturation stages. In addition, these results indicate that the
threshold EC, of the production function resulting from the application of saline
water during vegetative growth averages around 1/3 of the threshold salinity value
related to the application of saline water during the maturation stage.
Sinœ organs contributhg to various growth stages and yield components of
wheat develop at different phenological stages (Evans et al., 1 975; Kirby, 1 988),
environmental stresses affect their contribution to total grain yield differently
depending on when they occur (Frank et a1.,1987;Fnendf 1965; Halse and Weir,
1974; Langer and Ampong, 1 970). Maas and Grieve (1 990) reported that salinity
also affected yield components differentty depending on when plants were stressed
in the greenhouse.
Field experiments conducted on silty clay soi1 indicated that application of
saline irrigation water continuously throughout the growing season significantly
reduced al1 growth and yield conponents François and al. (1 994). Salinity imposed
during the vegetative growth stages reduced the number of spikelets per spike and
the number of tillen per plant; whereas salinity imposed in the flowering and
maturation stages only reduced kemel number and weight. Their results showed
grain yield reductions varying between 30% to more than 50% for wheat irrigated
continuously with saline water, cornpared to wheat irrigated with saline water only
during the flowering and maturation stages.
Under the real field conditions and practices in the amas studied. the effect
of using saline water during germination and early seedling stages on wheat yield
reduction is arnplified by the initial salintty of the seed bed which affects germination
percentage and seedling establishment and development (section 2.1.2).
4.3.2.2 Leaching fraction
The salt tolerance of wheat crop in the study areas is also affected by the low
leaching fraction usually applied. Due to water scarcity and low well productivity in
these semi-and areas, irrigation water is applied spanngly and more efficiently.
A seasonal averaged irrigation water balance an al ysis has been pe rfo rmed
to estimate the value of the seasonal leaching fraction applied in the Khabur and
Aleppo basins. The leaching fraction was computed using the following eguation:
LF = [( Di+Pe)/ETc]- 1
where Di, Pe and ET, are. respectively, the seasonai value of irrigation water
application, effective rainfall and wheat water requirements for evapotranspiration.
The applied seasonal leaching fraction over the study areas in the Khabur
basin and Aleppo basin averages 0.22 and 0.27 respectively. These values are
substantïally lower than the leaching fraction (LF=0.5) applied in the experimental
universal salt tolerance studies (Ayers and Westcot, 1985).
Table (4 -5) Estimation of the applieâ Ieaching fraction in Khabur basin and
Aleppo basins
Hassakeh (khabur basin) - - - - -
Boueider (Aleppo basin)
Rainfall
(mm)
Effective rainfall (')
Pe (mm)
Leaching fraction I 0.22 I 0.27
W heat water
requirement (mm)
Irrigation application
(mm)
') Estimated using U.S. Bureau of Recfamation method (1 970)
279
260
263
246
545
450 450
Various reports available in the literature show that crop threshold water
salinity values decrease sharply with a decrease in leaching fraction (van Hom et
al ., 1 993; PrenderFrost,l993; Hoffman et al., 1983; Bresler et al., 1 982). This is
malnly due to the increase of soi1 salinity in the root zone with the decreasing value
of leaching fraction (Bresler et al. 1982, Bernstein and François, 1973 and Bower et
al., 1 969). Recent experimental findings (van Hom et al., 1 993) show that for a
leaching fraction of 0.25. the wheat threshold value is less than 2 dSlm.
4.32.3 Summary
R is evident from the above discussions that various field conditions including
soi1 texture and structure, climate, irrigation water management and agricultural
practices affect salt tolerance of wheat. Because of inherent problems in integrating
the effeds of al1 of these factors, rigid water-quality standards for universal use are
difficult to develop. Therefore, the safe use of saline water necessitates the
developrnent of specific guidelines for different agro-ecological zones taking into
consideration the above cited factors.
5. SUMMARY AND CONCLUSIONS
5.1 Summary
A field research study was conducted in three semi-arid regions in Syria in
order to define, under field conditions, the wheat yield response function to
irrigation water salinity, the effect of soi1 textural and structural characteristics on
the irrigation water salinity threshold. and to compare this value with the
conventional aireshold value reported in the literature.The three reg ions were under
sirnilar climatic conditions (Mediterranean climate) but have different soi1 structure
and textures, varying from sandy loam to clay.
The study involved 74 farrns including 32 fams in the loamy clay/clay sail
area of the Khabur low valley plains, 30 fams in the clay loarn/loarn area of the
Aleppo south plains and 12 farms in the loardioarny sand area of the Shedadeh
area. The farms studied were selected using special cnteria. Namely, the fams had
been irrigating with saline water for more than 3 yean, and applying the same
cultural and irrigation management practices. W el1 water salinity in the selected
farrns varied between 0.44 dS/m and 14.1 dS/m.
The field study included collecting data on fam well water salinity, wheat
productivity and the corresponding relative yield at 74 fams for two agricultural
seasons: 1 99W 994and l994/l99S,soil samples for salinity analysis were collected
in the second year at hanrest time from 34 farms. Relative yield and Ec, (irrigation
water salinity, electrical conductivity) were correlated to obtain a yield response
function to irrigation water salin@ in each location and the corresponding threshold
water salinity value. Salt accumulation in the soi1 profile was rnonitored and, for
each region, the amount of salt accumulated in the soi1 profile (upper O - 80 cm)
was related to the ECw to assess the relationship between water salinity and the
resulting level of soi1 salt accumulation.
5.2 Conclusions
The Wheat yield response function to ECw, and hence the related irrigation
water salinity threshold values differed widely between the three locations; The
threshold value was: 1.2 dS/rn for the Khabur low plains (clay soil), 3.5 dSlm for the
Aleppo basin south plains(clay loam to loam soils) and 6.5 dS/m for the Shedadeh
area (loam to sandy loarn soil). These value are very close to irrigation water
salinity limits obtained in field studies conducted in different regions in the world.
For example, in lndia (1 .O dS/m for silty clay loarn, 4.0 dSIm for sandy loam and 6.0
dS/m for loamy sand) and in Tunisia (1.8 dS/m for clay soi1 and 3.5 dS/m for loamy
soi 1).
The observed discrepancy between water salinity limits for the three
locations rnay be attributed to factors related to difference in soi1 texture and
structure which affects soi1 infiltration capacity and water retention. These soi1
hydrologie characteristics influence salt development in the soi1 profile, which in
turn affects plant growth and yield. Analysis of the obtained soi1 salinity profiles
indicate that these differences in soi1 properties influence :
a) salt accumulation in the soi1 profile: Due to the good intemal drainability
and relatively low soi1 water retention, salt accumulation in the sandy loam soi1 area
(the Shedadeh region) was much lower than in the clay loam area (the Aleppo
south plains) and in tum even lower in the clay soi1 area (the Khabur valley low
plains). Therefore for the same level of irrigation water salinity, wheat is grown in
a more saline media in fine textured soils than in light textured soils and is exposed
to higher osrnotic potential which reduces its growth.
b) The level of seedbed salinity pressnt at sowing time: in fact, due to a lack
of rainfall during summer (Mediterranean clirnate), the salt accumulated in the soi1
profile during the last irrigation season creates saline seedbed conditions for the
ensuing wheat crop. Results of the analysis of soi1 salinity data indicate that for the
same irrigation water salinity level, initial seedbed salinity in the light textured soif
is around 25 to 50 % lower than in the heavy textured soils. Reports are available
in the fiterature which indicate that wheat is very sensitive to salt during germination
and early seedling growth, they show that increases of seedbed salinity affects
wheat germination and emergence, and adversely influences crop establishment
and productivity
c) The extent of *natural leaching" of the soi1 profile that can be acheived
during the rainy season (which, under the Mediterranean climate, constitutes a
dormant period separating seedling stages from the ensuing growth stages of
flowering and grain filling). Soil salinity profiles obtained at sowing time and after
winter rainfall indicate that due to their higher pemeability, reduction of soi1 salinity
in light textured soi1 resulting from winter rainfall is much higher than in fine textured
soil.This reduction in soi1 salinity will have a benefecial effect on the development
of the plant during the ensuing vegetative growth stage of flowerintg and grain
filling. Salinity stress at these stages is known to affect kemel number and weight
and can lead to a significant reduction in total grain yield.
Cornparison between imgation water salinity threshold value obtained in the
clay soi1 area of the Khabur valley low plains, (1.2 dS/m) and reported in the
conventional guidelines (4 dSlm) which were obtained from experiments conducted
in field plots on soi1 of same texture, shows large differences. This may be
attributed to the difference in imgation management between the fann real practices
and the experirnents procedures. Planting in the conventional sait tolerance studies
was under non-saline conditions (non-saline seedôed and irrigation with f res h water
during germination and eariy seedling stages) and irrigation water was applied
frequently with high leaching fraction.
Under real field conditions, sowing is done in saline seedbeds, resulting from
a progressive build-up of salinity from previous irrigation seasons. Results of this
study indicate that initial seedbed salinity increases with the increasing salinity of
imgation water. Saline seedbeds adversely influence germination percentage, crop
establishment, and ultimately crop yield. The problem is amplified by the use of
saline irrigation water during the germination and the early seedling stages.
Availble reports in the literature indicate that wheat is very sensitive to sait during
these stages.
The salt tolerance of a wheat crop under real field conditions is also affected
by the low leaching fraction which is of necessity practised. A seasonally averaged
irrigation water balance indicated that the applied leaching fraction in the Khabur
valley low plains averaged 0.22, which is much lower than the value of the applied
leaching fraction in the conventional wheat salt tolerance studies (LF = 0.5).
Reports show that the threshold value decreases sharply with a decrease in
leaching fraction.
The results of this research work indicate that wheat tolerance for irrigation
water salinity is affected by various real "in-field" conditions including soi1 texture
and structure, climate. irrigation water management and agricultural practices.
These results underline the necessity of establishing regional water quality criteria
when planning the use of saline water sources for irrigation. These criteria are of
prirnary importance for establishing suitable strategies for the safe use of saline
aquifers in Syria and other and and semi-arid regions.
6. RECOMMENDATIONS FOR FUTURE RESEARCH
The large expansion in the use of saline waters in Syria and in other semi-
and countries necessitates the implementation of field research projects aiming to
develop sustainable agricultural and irrigation management for the safe use of
saline aquifers and agricultural drainage water. The present research work has
identif ied the main subjects which could be covered by these research programs.
This includes the following :
a) Effect of leaching fraction in the development of soi1 salinity and crop
yield. This research work could study the effect the (number of irrigation
applications during the various crop growth stages) and the depth of irrigation, on
soi1 salinity and crop productivity.
b) Under the Mediterranean clirnatic conditions, study the effect of "natural
leaching" in the reduction of soi1 salinity. This research rnay study the effect of
integrating a fallow season during which the rainfall can ensure some natural
leaching in the crop rotation, on the soi1 salinity development and crop yield.
c) Effect of seeding rate on crop productivity.
d) In areas where non-saline water sources are available (non-saline
aquifers or surface water), study the effect of sequential use of non-saline water
(during early growth stages) and saline water ( during flowering and maturation
stages) on crop yield.
e) effect of pre-plant irrigation on reducing seed bed salinity and increasing
seedling emergence and improving crop yield.
f) study, under the field conditions, the salt tolerance of other wheat varieties
and cr ops.
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APPENDICES
Appendix A
Natural data
List of Tables in Appendix A
Table
A 4 Soil texture in Khabur low plains, Aleppo south plains and Shedadeh area
A-2 Soil-water characteristics in Khabur low plains, Aleppo south plains and
Shedadeh area
Table(3-2) Soil texture in Khabur low plains, Akppo south plains and
Shedadeh are%
Location
I
Khabur low plains
Shedadeh area
Aleppo south plains
Soil depth
(cm)
O - 2 0
20 - 40
40 - 60
60 - 80 80 - 100
0 -20
20 - 40
40 - 60
60 - 80 80 - 100
O -20
20 - 40
40 - 60
60 - 80
80 - IO0
Clay
(%)
41.9
57.4
60.6
60.8
62.7
31.2
28.3
22.6
21.4
16.9
30.0
39.8
45.3
45.1
41 -4
Silt
('+'O)
43.7
33.0
32.1
29.8
28.8 .
42.5
44.6
Sand
(W I
14.4
9.6
7.3
9.8
8.5 I
26.3
27.1
42.4
40.3
38.0
44.2
40.5
41.2
39.4
40.6
35.0
38.3
45.0
25.8
19.7
13.5
15.5
18.0
Table (3-3) Soil-watei characteristics in Khabui low plains, Aleppo south
plains and SMadeh area
--------. (% Moisture by weight at MPa)--------
Location
Khabur low plains
Shedaeh area
Aleppo south plains
Soil depth
0 -20
20 - 40
40 - 60
60 - 80
80-100
100-120
0 -20
20 - 40
40 - 60
60 - 80
80 - 100
100 -120
O -20
20 - 40
40 - 60
60 - 80
80 - 100
100 - 120
111 0
47.27
51.64
56.36
56.89
56.78
55.06
40.15
41.32
38.85
36.44
34.77
39.35
44.61
46.07
41.61
42.39
41.72
42.07
1 13
37.25
41.02
45.90
44.72
47.26
44.21
29.38
30.30
28.40
25.65
23.80
27.71
35.02
35.84
33.14
34.29
33.94
33.78
1 .O0
31.00
33.48
37.24
37.20
40.68
37.93
26.75
27.38
25.30
22.44
20.89
24.56
28.75
29.66
28.09
28.76
28.01
28.76
3.00
25.09
27.08
28.53
27.32
30.21
32.79
21.26
21.27
19.65
17.64
16.36
20.28
22.38
23.80
22.41
23.00
22.49
22.55
15.00
23.84
24.81
27.08
26.46
28.83
30.09
20.86
20.97
19.27
17.51
16.05
19.22
20.43
21.70
20.41
20.74
19.92
20.60
Appendix B
Wheat yidd date
199311 994 and 199M 995
List of Tables in Appendix B
Table
Wheat yield in farms using non-saline water, Aleppo basin
Wheat yield in farms using non-saline water, Khabur basin
Water salinity(EC,), wheat yield and wheat relative yield of
studied fams. Khabur low plains, 1 994/1995
Water salinity (ECJ, wheat yield and wheat relative yield of
studied fams, Khabur low plains, l993/1994
Water salinity (ECW), wheatyield and wheat relative yield of
studied fams, Aleppo south plains, 1994/1995
Water salinity (ECw), wheat yield and wheat relative yield of
studied fans, Aleppo south plains, 1993/1994
Water salinity (ECJ, wheat yield and wheat relative yield of
studied fams, Shedadeh area, 1994/1995
Water salinity (EC,), wheat yield and wheat relative yield of
studied farms, Shedadeh area, 1993/1994
Tabk B-la , Wheat yield in farms ushg non-dine water, Aleppo basin
I Yield (ma) 1
1 Sarakeb (1) 1 0.45 1 5.3 1 5.2 1 Sarakeb (2)
C
Tel-Hadya
0.48
r
lslamin
( Average 1 5.2
0.55
Sharaf
Table B-lb, Wheat yield in famm using non-saline water, Khabur basin
5.2
0.43
1 F a n name Yield (ma)
1
5.3
5.1
0.58
1 Bir Issa 1 0.54 1 5.0 1 5.2 1
5.4
5.2
1 Tel Brak
5.4
5.0 5.3
1 Nasserieh
Bir koko
Bir nouh
Total
Average
0.55
0.55
5.3
4.9
-- -
5.1
5.1
typical application is 10 cm of water
- KURBATIEH (3)
KHANASSER (1)
KHANASER (1)
KHANASER (3)
KHANASSER (4)
AL-SHARAF
HAMIDIEH (1)
HAMIDIEH (3)
TEL AHMED (2)
OM JRAN
l SLAM l N
RAMLA (4)
RAMLA (5)
14.1
11.55
10.00
9.70
9.70
0.64
12.7
7.5
2.7
1.66
0.43
1.28
3.19 (*) 1st number is the number of irrigation after sowing, 2nd number is the number of irrigations after winter
1 -25
2.13
2.86
3.25
3.64
4.375
2.02
3.86
5.03
5.2
5.3
5 .O0
3.90 rainfall. A
1 + 4
1 + 3
1 + 4
1 + 4
1 + 4
0 + 3
2 + 3
1 + 3
1 + 2
1 + 4
1 + 3
1 + 3
1 + 3
300
275
275
275
275
250
300
300
280
300
300
250
300
Cham 1
Cham 3
Cham 3
Cham 3
Cham 3
Cham 3
Cham 3
Djezireh
Cham 3
Acsad
Cham 3
Cham 1
Cham 3
0.24 ,
0.4 1
0.55
0.62
0.70
0.84
0.39
0.74
0.97
7 .O0
1 .O2
0.96
0.75
Table 6-6, Watei salinity (EC,), wheat yield and wheat relative yield of studled farms, Shedadeh area, 1994H995
typical application is 10 cm of water
L
Farm ECW Yield Irrigation(*) Seed Wheat Relative
5 71 i + n A
KARAT
KARAT IW L
y A n l A
6 51 1 + ?
7-44 4 ~ 7 1 + 4 m31
5 9
1 . - 7 3 -
R 6 3-75 n-73 I
R ~ - A 7 . 3 3 _ 6 6 1 R f i m ~
c;Q A GR ? q ~ 13-9 I A G n s ~ - -
(*) 1st number is the number of irrigation after sowing, 2nd number is the nurnber of irrigations after winter rainfall. A
Appendix C
Soil salinity data
List of Tables in Appendir C
Table
Soil salinity (ECJ, Khabur low plains
Soil salinity (ECJ. Aleppo south plains
Soil salinity (ECJ, Shedadeh area
I
S8' 1 r
GO* 1
ZO' 1 I
L'O L ' O 8'0 8.0 8'0 ZÇ'O Z
9'0 Ç'O S*O Ç ' O Ç ' O ÇS'O 1 1
ÇL'O 8'0 Ç9'0 8'0 L ' O ÇL'O 2
Z8'0 €8'0 L'O 8'0 €8'0 0'0 L r
8Ç.0 S9' O LE'O 8P'O LE ' O 1 P'O Z
ÇP'O 9'0 0Ç'O SÇ'O 9Ç.0 ZL'O C
61'2
1'2
10.2
86'0
8'0
19' 1
6* 1
ÇL' 1
SO' 1
9'0
L9' 1
ZÇ' 1
L* 1
ÇÇ' 1
20' 1
Ç8'0
--
L8' 1
L* 1
6' 1
SV* 1
6'0
90' 1
9' 1
95' 1
Ç 1'Z
P' 1
Ç6'0
GO' 1
Z
1
7:
1
Z
1
Tharnad -1
Bougha -3
Jem-Abiad
Dabaghieh
Srnehan Sh.
I Smehan Gh.
Abou-Anala
t
1 Oum-Hajra
1 L
2
1 r
2
1
2
1
2
1
2
1
2
1 1
2
1
2
2.52
2.55
3.04
2.52
3.14
2.51
3.5
2.78
5.32
4.55
4.64
4.28
4.91
5.54
6.74
5.95
2.55
1.92
2.92
2.55
2.1 1
2.71
2 .O5
2 -39
4.80
4.10
4.29
4.10
6.56
4.56
5.46
6.30
2.86
1 3 5
2.34
2.86
3.08
2.63
2.58
2.27
2.97
3.80
4.9
4.20
5.7
5.28
5.62
5.70
2.55
2.2
2.80
2.55
2.87
2.65
2.74
2.34
2.9 1
3.51
4.19
4.60
4.7
4.2
5.67
5.90
1.68
2.30
1.68
2.87
2.76
3.35
2.95
1 .O4
2.1 O
2.71
4.1 7
5.84
5.22
4.94
5.10
1.32
1.32
3.23
2.99
1.26
1.80
2,05
4.34
5.28
3.74
4.50
1 Om-Gharaph -3 1 1 1 2.02
1 Tal-Aran
1 Al-Raheb 1 1 5.44
l Khanasser
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