RAINWATER HARVESTING TECHNIQUES FOR
SOIL MOISTURE CONSERVATION ON THE
UPPER TERRACES OF THE
WHITE NILE STATE (Sudan)
By
ABDEL RAHMAN MOHAMED NOUR HAMID
B.Sc. Honours (Agric.) U. of K. 1984
M.Sc. (Agric.) U. of K. 1999
A Thesis
Submitted to the University of Khartoum in Fulfillment of the
Requirement for the Degree of Doctor of Philosophy
Supervisor: Dr. Omer Mohamed Eltom Elshami
Co-supervisor: Dr. Abdel Moneim Elamin Mohamed
Department of Agricultural Engineering
Faculty of Agriculture
University of Khartoum
Dec. 2004
1
DEDICATION
I dedicate the work to my mother with love and good wishes and to
my father with great gratitude and love, to my wife, to my children
to all my relatives, to all who helped me to complete this study
2
TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS
ABSTRACT
ii
ARABIC ABSTRACT iv
i
CHAPTER ONE: INTRODUCTION
1
CHAPTER TWO: LITERATURE REVIEW
2.1 Water harvesting
6
2.1.1 Rainfall and run-off 6
2.1.2 Definition of water harvesting 8
2.1.3 History of water harvesting
9
2.1.4 Causes and purposes of water harvesting
2.1.5 Water harvesting (catchment) techniques
2.1.5.1 Terrace techniques (bunds)
2.1.5.2 Run-off farming 21
2.1.5.3 Contour farming 21
6
11
13
15
2.1.5.4 Ridging and tie-ridging 23
2.1.5.5 Micro-catchment technique 24
2.1.6 Water harvesting in the Sudan 26
2.1.7 Water harvesting in Arab states 29
2.1.8 Limitations of water harvesting 32
2.1.9 Water harvesting in some world countries
2.2 Acacia nilotica tree (vernacular: Sunt) 34
2.2.1 Location and boundaries 34
2.2.1.1 Configuration and floods
35
2.2.1.2 Soil 36
2.2.1.3 Climate
39
2.2.1.4 Vegetation 39
2.2.1.5 Grasses and herbs 42
2.2.2 Afforestation and silvicutural treatments
3
33
43
2.2.2.1 Botany description (leafing, flowering, fruiting and seeds)
43
Page
2.2.2.2 Species
44
2.2.2.3 Distribution
45
2.2.2.4 Light relationship 46
2.2.2.5 Regeneration (Natural and Artificial) 46
2.2.2.6 Root system
47
2.2.2.7 Tending 48
2.2.2.8 Beating-up 48
2.2.2.9 Thinning 48
2.2.2.9.1 How the thinning technique is carried out?
50
2.2.2.9.2 Why the thinning technique is carried out?
2.2.2.9.3 Where the thinning technique is carried out?
50
51
2.2.2.9.4 When the thinning technique is carried out?
2.2.2.10 Rotation age
52
2.2.3 Injuries to which the crops are liable 52
51
2.2.3.1 Man 52
2.2.3.2 Animals
2.2.3.3 Insects
2.2.3.4 Birds
2.2.3.5 Plants
2.2.3.6 Fire 55
52
54
54
54
2.2.3.7 Wind
55
2.2.3.8 Thunder 55
2.2.4 Rate of Growth
55
2.2.5 Ownership and legal position
2.2.6 Uses 56
55
2.3 Acacia tortilis 57
CHAPTER THREE: MATERIALS AND METHODS 61
3.1 The study area 61
3.1.1 Location
61
4
3.1.2 Geomorphology and soils 63
3.1.3 Climate
64
Page
3.1.4 Landuse and vegetation 65
3.2 Layout of experimental field
66
3.3 Water conservation treatments (techniques)
3.4 Seedlings
76
3.5 Fencing 76
3.6 Meteorological data 76
69
3.7 Planting 77
3.8 Soil characteristic (soil mechanical and physical properties) 77
3.9 Infiltration rate (cm/h)
79
3.10 Soil moisture content (%) 82
3.11 Plant parameters measurements 82
CHAPTER FOUR: RESULTS AND DISCUSSION
4.1 Soil analysis 84
4.2 Soil physical properties
84
4.2.1 Soil bulk density 84
4.2.2 Infiltration rate
86
4.2.3 Soil moisture content (SMC)
84
87
4.3 The effect of the experimental treatments and sites on the
plant survival 93
4.4 The effect of experimental treatments and sites on the shoot
length (SL)
96
4.5 The effect of the experimental treatments and sites on
diameter at collar (DCR)
100
4.6 The effect of Experimental treatments and sites on the number
of branches per plant (NOB)
103
4.7 The effect of experimental treatments and sites on the plant
moisture content (PMC)
106
CHAPTER FIVE: CONCLUSIONS AND
RECOMMENDATIONS
5.1 Conclusions
5.2 Recommendations
110
111
5
REFERENCES
APPENDICES
112
126
LIST OF FIGURES
Figure
Title
Page
1.1
White Nile State
4
3.1
Location of the study area
62
3.2
The water tube level for surveying contours
67
3.3
Details of experimental design and field layout
70
3.3(a)
Details of semi-circular plots with curved bunds or
‘hoops’ to hold back runoff
73
3.3(b)
Details of microcatchment
74
3.3(c)
Details of rainwater strips
75
3.4
Double-ring infiltrometer
80
4.1
Soil bulk density
85
4.2
Infiltration rate (cm/h) and cumulative infiltration
(cm) versus elapsed time (min) for the three sites
88
4.3
Mean monthly rainfall at the experimental sites and
the long term average
90
4.4
Monthly soil moisture content (SMC)
measurements (wt %)
91
4.5(a)
Monthly plant survival measurements for Acacia
nilotica
94
4.5(b)
Monthly plant survival measurements for Acacia
95
6
tortilis
Figure
Title
Page
4.6(a)
Monthly shoot length measurements for Acacia
nilotica
97
4.6(b)
Monthly shoot length measurements for Acacia
tortilis
98
4.7(a)
Monthly diameter at collar measurements for
Acacia nilotica
101
4.7(b)
Monthly diameter at collar measurements for
Acacia tortilis
102
4.8(a)
Monthly number of branches measurements for
Acacia nilitica
104
4.8(b)
Monthly number of branches measurements for
Acacia tortilis
105
4.9(a)
Monthly plant moisture content measurements for
Acacia nilotica
107
4.9(b)
Monthly plant moisture content measurements for
Acacia tortilis
108
7
ACKNOWLEDGEMENT
I would like to express my gratitudes and thanks and deep
appreciation to Dr. Omer Mohamed Eltom Elshami and Dr. Abdel
Moneim Elamin Mohamed for their helpful criticism, inspiring
guidance, consistent supervision and valuable advice. I am extremely
grateful and highly thankful to Dr. Abdel Azim Yassin for his highly
appreciable help and advice on the experimental design and statistical
analysis of the data. Also, my sincere appreciation to Dr. Abdel Aziz
Karam Alla for suggestion the subject of this study.
I wish to express my appreciation to the member of the Soil
Laboratory for their cooperation. I would take this opportunity to
thank the Forests National Corporation especially the Manager of
White Nile State Sector (Kosti), and his staff for their trust and help in
all experiment stages. Also, acknowledgement is due to the people at
the experiment sites for their highly advice, cooperation and help.
Appreciation is also extended to all staff members of Dept. of
Agric. Engineering, Faculty of Agriculture, University of Khartoum
and all who encouraged and help me to complete this study.
Also, acknowledgement due to Abdel Aziz Ahmed and Salah
Mohmed for their help and cooperation. Special thanks to Mrs.
Elmagam Ali Hassan and Miss Bilghies Hassan for typing this work.
ABSTRACT
8
Field experiments were conducted at Humra, Aba, and Kileikis,
White Nile state, Sudan, on a sandy clay soil, following a randomized
block design, to study the effect of water harvesting techniques
namely: crescents, intersections, ditches and control treatments on
some soil physical properties and soil moisture content. The soil
moisture content was measured monthly immediately after the rainy
season till the beginning of the next season during 2003/04 growing
season. Also plant parameters of Acacia nilotica and Acacia tortilis
transplants were measured monthly immediately after the rainy season
till the next season. Direct rainfall was measured using rain gauges
which were installed on the field.
The results indicated that the water harvesting techniques
affected the soil structure and soil physical properties specially on the
upper layer (0–30 cm) which subjected to excavation tools and
consequently the soil moisture content as a result of improving
infiltration rate, porosity, field capacity and reducing rain water
runoff.
The results revealed that the crescents treatment was the best
technique for improving porosity, infiltration rate, soil storage
capacity and reducing runoff which led to a good performance
of
Acacia nilotica and Acacia tortilis transplants. The intersections
techniques came next to the crescents in storage capacity and
performance of the plants.
Also the results showed no significant differences between
ditches and control treatments.
9
The results indicated that the Acacia nilotica transplants gave
good results when the moisture content increased while Acacia tortilis
transplants gave good results when the moisture content decreased.
10
‫‪Π‬‬
‫ﻣﻠﺨﺺ ﺍﻷﻃﺮﻭﺣــﺔ‬
‫ﺃﺠﺭﻴﺕ ﺍﻟﺘﺠﺎﺭﺏ ﺍﻟﺤﻘﻠﻴﺔ ﺒﻤﻨﻁﻘﺔ ﺍﻟﺤﻤﺭﺓ ﻭﺍﻟﺠﺯﻴﺭﺓ ﺃﺒﺎ ﻭﻜﻠﻴﻜـﺯ – ﻭﻻﻴـﺔ ﺍﻟﻨﻴـل‬
‫ﺍﻷﺒﻴﺽ ﻓﻲ ﺘﺭﺒﺔ ﺭﻤﻠﻴﺔ ﻁﻴﻨﻴﺔ – ﺒﺎﺴﺘﺨﺩﺍﻡ ﺘﺼﻤﻴﻡ ﺍﻟﻤﺴﺘﻁﻴﻼﺕ ﺍﻟﻌﺸﻭﺍﺌﻴﺔ ﻟﺩﺭﺍﺴـﺔ ﺘـﺄﺜﻴﺭ‬
‫ﺘﻘﻨﻴﺎﺕ ﺤﺼﺎﺩ ﻤﻴﺎﻩ ﺍﻷﻤﻁﺎﺭ )ﺍﻟﻬﻼﻻﺕ ﻭﺍﻟﺘﻘﺎﻁﻌﺎﺕ ﻭﺍﻟﺠﺩﺍﻭل ﻭﺍﻟﻁﺭﻴﻘـﺔ ﺍﻟﺘﻘﻠﻴﺩﻴـﺔ( ﻋﻠـﻰ‬
‫ﺒﻌﺽ ﺍﻟﺨﻭﺍﺹ ﺍﻟﻔﻴﺯﻴﺎﺌﻴﺔ ﻟﻠﺘﺭﺒﺔ ﻭﺒﺎﻟﺘﺎﻟﻲ ﻋﻠﻰ ﺍﻟﻤﺤﺘﻭﻯ ﺍﻟﺭﻁﻭﺒﻲ ﻟﻠﺘﺭﺒﺔ ﺍﻟﺫﻱ ﺘـ ‪‬ﻡ ﻗﻴﺎﺴـﻪ‬
‫ﺸﻬﺭﻴﹰﺎ ﻤﺒﺎﺸﺭﺓ ﺒﻌﺩ ﺍﻨﺘﻬﺎﺀ ﻓﺼل ﺍﻟﺨﺭﻴﻑ ﺨﻼل ﻤﻭﺴﻡ ﺍﻟﺩﺭﺍﺴﺔ ‪ 2003/04‬ﻭﺤﺘـﻰ ﺒﺩﺍﻴـﺔ‬
‫ﺍﻟﺨﺭﻴﻑ ﺍﻟﺘﺎﻟﻲ ﻭﺃﻴﻀﹰﺎ ﺘ ‪‬ﻡ ﻗﻴﺎﺱ ﺃﺩﺍﺀ ﺸﺘﻭل ﺃﺸﺠﺎﺭ ﺍﻟـﺴﻨﻁ ‪ Acacia nilotica‬ﻭﺸـﺘﻭل‬
‫ﺃﺸﺠﺎﺭ ﺍﻟﺴﻴﺎل ‪ Acacia tortilis‬ﺤﻴﺙ ﺘ ‪‬ﻡ ﻗﻴﺎﺱ ﺍﻷﺩﺍﺀ ﻟﺠﻤﻴﻊ ﺍﻟﻤﻌﺎﻴﻴﺭ ﺸﻬﺭﻴﹰﺎ ﺒﻌﺩ ﺍﻨﺘﻬـﺎﺀ‬
‫ﻓﺼل ﺍﻟﺨﺭﻴﻑ ﻤﺒﺎﺸﺭﺓ ﻭﺤﺘﻰ ﺒﺩﺍﻴﺔ ﺍﻟﻤﻭﺴﻡ ﺍﻟﺘﺎﻟﻲ ‪ .‬ﻜﻤﺎ ﺘ ‪‬ﻡ ﻗﻴﺎﺱ ﻜﻤﻴﺎﺕ ﺍﻟﻤﻁـﺭ ﺍﻟﻤﺒﺎﺸـﺭ‬
‫ﺒﻭﺍﺴﻁﺔ ﻤﻘﺎﻴﻴﺱ ﺍﻷﻤﻁﺎﺭ ﺍﻟﺘﻲ ﺭﻜﺒﺕ ﻓﻲ ﺍﻟﺤﻘل‪.‬‬
‫ﺃﻭﻀﺤﺕ ﺍﻟﻨﺘﺎﺌﺞ ﻭﺠﻭﺩ ﺘﺄﺜﻴﺭ ﺘﻘﻨﻴﺎﺕ ﺤﺼﺎﺩ ﻤﻴﺎﻩ ﺍﻷﻤﻁﺎﺭ ﺍﻟﺘﻲ ﺃﺴـﺘﺨﺩﻤﺕ ﻭﻫـﻲ‬
‫ﺍﻟﻬﻼﻻﺕ ﻭﺍﻟﺘﻘﺎﻁﻌﺎﺕ ﻭﺍﻟﺠﺩﺍﻭل ﻭﺍﻟﻁﺭﻴﻘﺔ ﺍﻟﺘﻘﻠﻴﺩﻴﺔ ﻋﻠﻰ ﺘﺭﻜﻴﺒـﺔ ﺍﻟﺘﺭﺒـﺔ ﻭﺒﺎﻟﺘـﺎﻟﻲ ﻋﻠـﻰ‬
‫ﺨﻭﺍﺹ ﺍﻟﺘﺭﺒﺔ ﺍﻟﻔﻴﺯﻴﺎﺌﻴﺔ ﺨﺎﺼﺔ ﻓﻲ ﺍﻟﻁﺒﻘﺔ ﺍﻟﻌﻠﻴﺎ )ﺼﻔﺭ – ‪ 30‬ﺴﻡ( ﺍﻟﺘﻲ ﺘـﺄﺜﺭﺕ ﺒﻤﻌﺎﻤﻠـﺔ‬
‫ﺍﻵﻟﻴﺎﺕ ﻤﻤﺎ ﺃﺜﺭ ﻋﻠﻰ ﺍﻟﻤﺤﺘﻭﻯ ﺍﻟﺭﻁﻭﺒﻲ ﻨﺘﻴﺠﺔ ﻟﺘﺤﺴﻴﻥ ﻤﻌﺩل ﺍﻟﺘﺴﺭﺏ ﻭﺍﻟﻤﺴﺎﻤﻴﺔ ﻭﺍﻟـﺴﻌﺔ‬
‫ﺍﻟﺘﺨﺯﻴﻨﻴﺔ ﻟﻠﺘﺭﺒﺔ ﻭﺘﻘﻠﻴل ﺍﻟﺠﺭﻴﺎﻥ ﺍﻟﺴﻁﺤﻲ ‪ .‬ﻜﺫﻟﻙ ﺃﻭﻀﺤﺕ ﺍﻟﻨﺘـﺎﺌﺞ ﺍﻥ ﺍﻟﻬـﻼﻻﺕ ﻜﺎﻨـﺕ‬
‫ﺃﺤﺴﻥ ﺍﻟﺘﻘﻨﻴﺎﺕ ﺍﻟﻨﻲ ﺃﺩﺕ ﻟﺘﺤﺴﻥ ﻭﺍﻀﺢ ﻓﻲ ﺍﻟﻤﺴﺎﻤﻴﺔ ﻭﻤﻌﺩل ﺍﻟﻨﻔﺎﺫﻴﺔ ﻭﺍﻟـﺴﻌﺔ ﺍﻟﺘﺨﺯﻴﻨﻴـﺔ‬
‫ﻟﻠﺘﺭﺒﺔ ﻭﺘﻘﻠﻴل ﺍﻟﺠﺭﻴﺎﻥ ﺍﻟـﺴﻁﺤﻲ ﻤﻤـﺎ ﺃﺩﻯ ﺍﻟـﻰ ﺃﺩﺍﺀ ﺠﻴـﺩ ﻟـﺸﺘﻭل ﺃﺸـﺠﺎﺭ ﺍﻟـﺴﻨﻁ‬
‫‪ Acacia nilotica‬ﻭﺸﺘﻭل ﺃﺸﺠﺎﺭ ﺍﻟـﺴﻴﺎل ‪ . Acacia tortilis‬ﺜـﻡ ﺠـﺎﺀﺕ ﻤﻌﺎﻤﻠـﺔ‬
‫ﺍﻟﺘﻘﺎﻁﻌﺎﺕ ﻓﻲ ﺍﻟﻤﺭﺘﺒﺔ ﺍﻟﺜﺎﻨﻴﺔ ﻟﻠﻬﻼﻻﺕ ﻓﻲ ﺘﺨﺯﻴﻥ ﺍﻟﻤﺎﺀ ﻭﺠـﻭﺩﺓ ﺃﺩﺍﺀ ﺍﻟـﺸﺘﻭل ‪ .‬ﻜﻤـﺎ ﺃﻥ‬
‫ﺍﻟﻨﺘﺎﺌﺞ ﻟﻡ ﺘﻅﻬﺭ ﺃﻱ ﻓﺭﻭﻗﺎﺕ ﻤﻌﻨﻭﻴﺔ ﺒﻴﻥ ﻤﻌﺎﻤﻠﺔ ﺍﻟﺠﺩﺍﻭل ﻤﻥ ﻨﺎﺤﻴﺔ ﻭﺒﻴﻥ ﺍﻟﻤﻌﺎﻤﻠﺔ ﺍﻟﺘﻘﻠﻴﺩﻴـﺔ‬
‫ﻤﻥ ﻨﺎﺤﻴﺔ ﺃﺨﺭﻯ‪.‬‬
‫ﻜﺫﻟﻙ ﺃﻭﻀﺤﺕ ﺍﻟﻨﺘﺎﺌﺞ ﺍﻥ ﺸﺘﻭل ﺃﺸﺠﺎﺭ ﺍﻟﺴﻨﻁ ‪ Acacia nilotica‬ﺃﻋﻁﺕ ﻨﺘﺎﺌﺞ‬
‫ﺃﻓﻀل ﺒﺯﻴﺎﺩﺓ ﺍﻟﻤﺤﺘﻭﻯ ﺍﻟﺭﻁﻭﺒﻲ ﻤﻘﺎﺭﻨﺔ ﺒﺸﺘﻭل ﺃﺸﺠﺎﺭ ﺍﻟـﺴﻴﺎل ‪ Acacia tortilis‬ﺍﻟﺘـﻲ‬
‫ﺃﻋﻁﺕ ﻨﺘﺎﺌﺞ ﺃﻓﻀل ﺒﺎﻨﺨﻔﺎﺽ ﺍﻟﻤﺤﺘﻭﻯ ﺍﻟﺭﻁﻭﺒﻲ ﺨﻼل ﻤﻭﺴﻡ ﺍﻟﺩﺭﺍﺴﺔ‪.‬‬
‫‪11‬‬
CHAPTER ONE
INTROD UCTION
One of the major critical problems of Agriculture is water
conservation, especially in rainfed areas. Sound soil and water
conservation is based on the full integration of engineering, plant
and soil sciences. It is essential to develop sound practice that will
permit the entrapment and storage in soil profile a greater
percentage of available precipitation such a procedure referred to
as water harvest, is providing an entirely new potential source of
water.
In the water deficient arid regions of the Sudan the
availability of water sources, throughout the year, and fertile
lands have largely determined the population distribution pattern.
The inhabitants of these areas such as the southern parts of
Darfur and Kordofan have devised several indigenous ways of
collecting and storing rainwater for human and animal
consumption during the dry season. Some of these techniques
occurred naturally, whereas others have been constructed or
modified by man. Haffirs, some dams, wells, Fulas, Turdas, Serat,
Rock walls, Boabab tree trunk storage, cisterns, tanks, burnt clay
pots, barrels and empty oil drums are techniques adopted to
increase the year round availability of water, for human and
animal consumption, in different parts of the Sudan. The water
12
provided by these supply sources, which are generated mainly
from rainwater runoff, is below the needs of the inhabitants. This
is because, in most seasons, the potential runoff water exceeds the
storage capacity of the local systems. The excess water can be
utilized for crop production in these areas where rainfall is low
and erratic.
The clay plain region of central Sudan occupies a large part
of the broad central belt across the country from east to west,
intermediate between the desert of the north and the heavy
rainfall area of the south. It is the most developed portion of the
country and play a major part in the national economy. Located
in that region are irrigated schemes, the mechanized crop
production scheme dependent on rainfall, a large part of grazing
ground and gum arabic producing tract and the major
concentration of population, including almost all the large towns.
These developments put pressure on it’s a scanty natural
forest resources, mainly partly stocked savanna woodland. The
problems of meeting the demand, already serious, is likely to
increase with the population and the growth of wood using
industries in the towns.
Aforestation in the region itself is the most practical solution
to meet the demand and to stop desert creeping at the north part
of the region mainly the north White Nile State which was also
subjected to series of drought intervals since the early eighties,
13
which has severely affected the life of people in the region. The
site factors are unfavorable to fast growth of trees, and produced
the formation of dense crops, also any plants introduced have to
face hazards such as grazing by animals.
This study is concerned with the techniques of aforestation
in White Nile State in the areas that lie along White Nile on both
side. Most of these areas are not flat i.e the contour surveying
revealed a difference in level between the higher off-flow areas
and the low on-flow areas towards the White Nile. Consequently
the water shortage problem prevails in the area, hence the
establishment of forest plantation is a problem of research level,
because little or no water is available to plant roots. At the end of
the rainy season the seedlings were only few centimeters in height,
the soil dries rapidly and the small seedlings soon die.
White Nile State (Fig. 1.1) is a productive area from
agricultural and animal points of view, due to its moderate soil
fertility and climate suitability. Many people are primarily
rainfed subsistence cultivators, whereas others depend on herd
stocking and dry season irrigated schemes along the banks of the
White Nile. The high crop yields and heavy rains that have
characterized the area before and during the seventies have
markedly started to decline. The meteorological data at a number
of stations in White Nile State showed marked variations and poor
distribution of rainfall during the last three decades. At White
Nile, a ten year interval (Table 1 Appendix A) for the five periods
14
1953-62, 1963-72, 1973-82, 1983-92 and 1993-2002 showed a
variation in mean annual rainfall totals from 733.0 mm to 680 mm
to 565.0 mm to 460 mm and to 490 mm, respectively.
15
16
The study deals only with water running off surfaces on
which rain has directly fallen, not with stream flow. Rainwater
harvesting, as a potential source of water for agriculture, has been
the focus of much attention in recent years, although there is
along history of rainwater harvesting in Sudan. The techniques
under study are consistent with cultural and economic structure,
available resources and the long experience of the local farmers.
The magnitude of the vast sites is seen in the total areas that
lay far away from the White Nile on both sides. This work is
planned to improve our understanding in the utility of these sites
under agriculture. Therefore the objectives of this study were:1-
Applying treatments to maximize the use of surface runoff
water on sloping lands.
2-
To compare different water harvesting techniques on the
basis of soil water conservation to determine the most suitable
practice under studied areas.
3-
Improving the soil physical condition (through the soil
work) to increase water penetration and improve soil aeration.
4-
Provision of different means of water conservation to be
adopted by farmers under various conditions.
17
CHAPTER TWO
LITERATURE REVIEW
2.1 Water harvesting
Rainwater harvesting has attracted considerable attention in
recent years in work covering a wide range of techniques, from the
collection of rainwater from roofs to the retention of surface and
subsurface flow in rivers. The main interest of the researchers has
been methods of collecting and conserving rainwater as at early stage
as possible in the hydrological cycle to ensure the best use of rainfall,
before it has run away into rivers and groundwater, or has disappeared
as evaporation. Additional benefits from such measures of water
control will often include a reduction in both soil erosion and in the
damage caused by flooding. For the purposes of the study, rainwater
harvesting, has been defined as the gathering and storage of water
running-off surfaces on which rain has directly fallen and not the
harvesting of valley flood water or stream flow.
2.1.1 Rainfall and run-off
Among the various factors affecting life and development in all
parts of the world is water. Rainfall is the basic source of water and
because of its seasonal and variable nature, it is greatly limiting water
availability for the different purposes, especially agriculture. Not all
rain-water is available to plants (effective) because some losses occur
in forms of evapotranspiration, deep percolation beyond the root zone
18
and surface run-off. If not properly utilized, surface run-off can be the
major form of water loss.
Run-off is the portion of the precipitation which makes its way
towards stream channels, lakes, seas or oceans (FAO, 1987). It is
divided into surface, sub-surface and ground water components
(Dubried, 1985). The water that travels over the ground or in stream
channels is the surface run-off (overland flow). In the upper layers of
the soil, sub-surface lateral movement of water which has infiltrated
may be considerable (through-flow or inter-flow) and may re-emerge
at some point on the surface (return flow) and reaches streams or
lakes. However, movement is less rapid than that of overland flow.
Surface run-off and inter-flow are viewed as direct run-off, which
dominates the cumulative run-off, because no adequate method exists
to separate them (Taur and Humborg, 1992). Some water may
percolate to deeper layers to become ground water some of which by
lateral movement, may eventually, seep into streams, lakes or oceans
as ground water run-off or ‘base flow’ (Jackson, 1989). Moreover,
rainfall occurring where the main water table intersects the surface
will also produce saturation overland flow.
Surface run-off develops either when rainfall intensity exceeds
the infiltration capacity of the soil (Bache and MacAskill, 1984) or
when the volume of rainwater exceeds the storage capacity of the soil
(Dunne and Black, 1970). In the former mechanism surface run-off
occurs before the soil has become fully saturated, so it is more
19
appropriate on bare shallow soils and on upper slopes. While in the
latter mechanism, surface run-off occurs after saturation of the soil,
even with rainfall of low intensity and volume, because it occurs
particularly in soils with shallow water tables. Thus, it is more likely
on areas near drainage channels (Taur and Hunaborg, 1992) or with
topsoil layers overlying an almost impermeable subsoil or rock
(Betson and Marius, 1969). In both cases, run-off occurs on a partial
area basis after the surface depressions are filled with water (FAO,
1991). For these reasons, short lived intense storms contribute more
to run-off than the prolonged storms of low intensity (Hudson, 1981
and Morgan, 1986). This is because in the former case the infiltration
capacity of the soil is exceeded, whereas in the latter case most of the
rainwater infiltrates into the soil.
2.1.2 Definition of water harvesting
Rain water harvesting can be defined to comprise the harvesting
of run-off from roofs, artificial surface at ground level and land
surface with slope. The term “water harvesting” has many definitions
according to the method and purpose of water storage. The essence of
water harvesting is the collection and storage of water for use.
Rain water harvesting has been defined by Pacey and Cullis
(1986) as the gathering and storage of run-off water surfaces on which
rain has directly fallen, and not the harvesting of valley flood, water or
stream flow. This definition is suitable for water harvesting for
domestic uses rather than for agricultural purposes due to the limited
20
amount of water that will be collected. Whereas Pieck (1985) defined
the rain water harvesting concept as: (The collection and storage of
any surface run-off water). While Ferguson (1987) defined water
harvesting concept as the generation of rainfall run-off and the
collection of that run-off for use. Nevertheless, Proud (1988) defined
the water harvesting as the interception and concentration of rainfall
run-off and its storage in the soil profile for use by crops, grasses or
trees. By supplying the plants with run-off water in addition to rainfall
it is essentially a form of low cost natural irrigation. The principle of
collecting and using precipitation from a small catchment area is often
referred to as rain water harvesting. Water harvesting can also be
described as the complete facility for collecting and storing the run-off
water (FAO, 1994). These are generalized definitions which depend
on generation, collection and utilization of surface run-off for different
purpose such as livestock drinking, domestic uses and growing of
plants. Schwab and Frevert (1985) have defined rain water harvesting
as any water shed manipulation carried out to increase surface run-off.
2.1.3 History of water harvesting
This method began in the Bronze age when desert dwellers
smoothed hills sides to increase rain water run-off and built ditches to
collect rain water and convey it into lower lying crop fields. The rain
water harvesting techniques have ancient roots in the arid areas,
supplying water for agriculture and fresh water for residence
(Ferguson, 1987). The rain water harvesting as a method is almost
21
4000 years old. The early history of rain water harvesting has its
origin in Europe. During the Roman Empire, around the fourth
century (B.C.), people used to construct reservoirs to store run-off
water (UNICEF, 1989). It started by using simple water storage
facilities such as natural depressions in rock or soil surfaces (Tauer
and Humborg, 1992). Signs of early water harvesting structures in the
Edom mountain in southern Jordan believed to have been developed
about 9000 years ago (FAO, 1994). Agriculture in the Old World
originated in a climatically dry region in the Middle East, and may
have depended to some degree on irrigation or run-off farming
methods from the start (Eveuari;Mashash, 1973). The techniques
involved seem to have been forgotten in subsequent agricultural
development located in moist regions of Europe, Asia and America.
The most notable evidence about such techniques in the Ur area in
Iraq and in the Negev desert, in southern Israel. It is clear that in this
region, rain water provided a livelihood for a considerable population
more than 2000 years ago (Thames and Ficher, 1981).
Water harvesting techniques had been developed and improved
to keep pace with the growing needs for water for agricultural and
domestic purposes. Roof and micro-catchment were used to harvest
water which has been stored in small reservoirs and tanks. A rapid
increase in water harvesting techniques and storage began in different
parts of the world such as India, China, Palestine, Sudan, Iran and
Kenya. This rapid increase had contributed to the opportunity of
22
modern materials to be used in constructing the storage tanks and
catchment surface. Dams and large reservoir were constructed using
the Ferro-cement, steel, cement and other materials to harvest and
store water. In some arid zones water is harvested and stored in dams
for domestic uses as in Australia (UNICEF, 1989).
2.1.4 Causes and purposes of water harvesting
In order to meet future food and water needs, attention has to be
focussed on better use of all available water resources by employing
all possible techniques.
Water harvesting is an ancient method of water supply that has
recently received more attention as a potential source of water,
especially on areas of erratic and uneven distribution of rainfall, where
irrigation facilities are not available. The main purposes for collecting
rain water are to provide adequate water for arable lands, range land,
fishing industries, domestic uses, animal consumption, strategic
purposes (defensive purposes), recreational purposes and wildlife
consumption. When the goal is to store water, as soil moisture, to
support the plant growth the practice is sometimes referred to as
run-off farming (Eger, 1989).
Agriculture is the major user of water, with an average of 69%
over the world, followed by industry, with 23% and domestic uses
(cities) with 8% (FAO, 1997b). The World Meteorological
Organization (Spore, 1997) has estimated that water use had tripled in
23
the last two decades and has been increasing at twice the rate of
population growth.
Water is a limiting factor for all sources of life including man,
animal and plant. The inadequacy of water is becoming and will be a
vital problem threatening the life and development of the increasing
world population. Water harvesting system is practiced in the arid and
semi arid zones where annual rainfall is insufficient for plant
requirements either for poor rainfall or rain water is not available to
plant root zone, which may be for one or more of the following
reasons:1.
Steep slope of the location, hence sheet flow run-off of rain
storms immediately runs to the water natural channels, so that the
depth of infiltration is not enough for the plant.
2.
Low soil infiltration rate e.g. heavy clay soil, on which the first
drops of rain beat the soil surface into compact impermeable clay
layer.
3.
Clay soil e.g. Gardud and Nagaa soils.
There is one interesting point to mention, that the water
harvesting system has no meaning in case (2, 3) unless it is combined
with deep ploughing and should be constructed along contour lines to
intercept run-off (Badi, 1965).
According to Proud (1988), the strategies to improve the
availability of soil moisture for use by trees and crops can be
enhanced by managing the supply of water so that losses through
24
run-off and evaporation are minimized and managing the trees and
crops to reduce their demand for moisture.
In supply management the amount of rainfall available to roots
can be increased by increasing the rate and depth of infiltration into
the soil, reducing evaporative losses by mulching, and intercepting
and concentrating run-off by water harvesting. Such a procedure is
referred to as water harvest, which is provides an entirely new
potential surface source of water (Schwab, 1966).
2.1.5 Water harvesting (catchment) techniques
Engineers have concentrated their efforts on the major rivers,
seeing them, perhaps, as ‘a sort of challenge’, and considering how
many dams they could build on them, how great a command area
could be created, and so on. But for the vastly greater areas of the
world’s surface that are outside big river systems, they had virtually
nothing to offer (Ionides, 1976).
Water harvesting is based on the utilization of surface run-off
and requires a run-off area (catchment area), for collecting and
concentrating the precipitation, and a storage area (storage facility) for
holding the collected water for later use (FAO, 1994). The harvested
water will either be collected from direct rainfall or from rain water
run-off which is generated from different types of catchments (water
harvest areas). FAO (1998) has defined the catchment or watershed as
the area which supplies water by surface and subsurface flows from
rain to a given point in the drainage system. Different types of
25
catchments are used, in tropical and semi-arid areas, to utilize rain
water such as roof tops, artificial and natural soil surfaces. Catchment
area can vary in size from a few square metres to several square
kilometres.
The storage areas could be in the form of above ground tanks,
excavated cisterns, small dams or ponds and soil profile.
There are different forms of water harvesting:1-
roof top harvesting
2-
water harvesting for animal consumption
3-
inter-row water harvesting
4-
catchment water harvesting (which includes micro, medium and
large catchment water harvesting (Pacey and Cullis, 1986).
Basically the catchment is an artificial or natural ground surface
which has been specially prepared and demarcated to generate water
run-off to be utilized. There are several types of catchments used in
rain water harvesting as roofs tops catchment, artificial surface
catchment and the natural surface catchment, where the ground
surface must be suitable for rain water harvesting. Also the ground or
catchment surface should have a degree of slope so that run-off can
easily be generated. It is very important that the soil must be relatively
impermeable and with gentle slope towards the storage area. There are
several methods and techniques of natural surface catchment which
are used to provide water for agricultural purpose such as contour
furrows, micro-catchment techniques, terrace techniques, inundation
26
techniques, flood water techniques and run-off farming techniques by
building high bunds, banks or terraces along the contour. Water will
infiltrate slowly or evaporate and thereby crops can be planted (Cullis,
1986).
2.1.5.1 Terrace techniques (bunds)
Such technique is found in most parts of central Sudan
particularly in areas with clay soils. The terrace is a relatively elevated
land non flooded by khors to utilize run-off water on steep slopes.
This is accomplished by constructing U-shaped bunds across the slope
of rolling land to trap sheet flow run-off generated after rain storms on
catchment usually 2-3 times the size of the cultivated land (Van Dijk,
1991).
Terraces are earth embankments or combined channels and
earth embankments constructed across sloping land, at fixed vertical
intervals, down the slope (FAO, 1976). Hudson (1981) stated that any
earthen bank with strip of land above it is called a bund, a terrace or a
contour ridge.
Terracing has also been defined by Das (1977) as a series of
mechanical barriers across the land slope to break the slope length and
also to reduce the slope degree wherever necessary. This definition
indicates that the main function of terracing is to break up the slope,
shorten the effective length and degree of the slope of the land and
hold back run-off, thus reducing the hazard of erosion by run-off. Also
through collecting, controlling and safely conveying the excess water,
27
terracing can encourage water infiltration, improve moisture
conservation and crop yield (FAO, 1971).
Terraces are called by different names in different countries and
according to the purpose of construction. This method is also widely
used in the Indian high lands, Yemen and mountainous part of Kenya.
It is possible to construct either straight or curved terraces. The
straight terraces either be short or long terraces on the contour lines.
The short terraces not longer than 3-6 m and placed alternatively or
distributed on the slope depending on the topography. For the long
terrace it is important to divide them into small sectors by regular
smaller space at intervals repeated every 3-4 m to drain the run-off to
the natural water ways and outlets can be done when necessary at both
ends of the terrace to control erosion. The curved terrace or (crescentshaped) also known as micro-basin (Fig. 1 Appendix B) is suitable for
places where extremely rough terrain exists (FAO, 1976). This last
terrace was adopted by Badi (1965) in arid clay plain of Kassala
province in Malawiya and Hamatieb. The species used were Hashab
(Acacia senegal), Neem (Azadirachta indica), Prosopis juliflora and
Eucalyptus microtheca. The plants died immediately after the end of
the rainy season. The rains in 1963 were poor. However, few plants
survived in water collecting sites. The trial was repeated in 1964 in
Hamatieb with Eucalyptus microtheca, Conocarpus lanifoluis and
Azadirachta indica. Each species was planted in a single line. In
Malawiya the planting was done with Prosopis juliflora and Acacia
28
senegal. The rainy season was very good with well distributed
showers. The plantation in Malawiya failed except in water collecting
sites, the plantation in Hamatieb was only possible in years of good
rain and in better water collecting sites (Badi, 1865).
Terraces design should be adapted to the hydrological erosion
control of the treated area (Schwab, 1966).
Improperly designed and constructed, terraces can create many
problems to farmers. The exposure of less fertile subsoil of shallow
soils may reduce crop yields. Irregular terrace layout, on irregular
slopes, can retard the use of farm machinery (Kohnke and Bertrand,
1959). Terrace failure and the consequent damaging runoff and land
sliding is also common in case of severe storms (Hudson, 1981).
According to Schwab (1966) channels cross sections have
been modified to become more nearly compatible with modern
mechanization, the following types of terraces are identified:a) The broadbase terrace
Which removes or retains water on sloping land. This type has a
wide use for control of run-off, for erosion control and for moisture
conservation. The long process of development of the broadbase
terrace has led to a variety of types, terms and classification. On the
basis of construction they are classified as the Nichols or channel
terrace which is constructed from the upper side only and the Mangum
or ridge terrace is constructed from both sides. Abroad terrace is a
broad surface channel or embankment constructed across the slope of
rolling land. On the basis of the primary function the broadbase
terrace is classified as graded or level. In most area graded or channeltype terraces which are constructed from the upper side only are more
29
effective in reducing erosion than run-off, whereas level or ridge-type
terraces which are constructed from both sides are effective in
reducing run-off as well as controlling erosion, i.e. the primary
purpose of this type of terrace is moisture conservation and erosion
control as a secondary objective. In low-to-moderate rainfall regions
they trap and hold rainfall infiltration into the soil profile (Schwab,
1966).
b) The bench terrace
The early conventional bench terrace system consisted of a
series of flattened shelf-like areas that converted a steep slope of 20 30% to a series of level or nearly level bench (large step or level
benches) this type is limited where extremely rough terrain exists. The
early conventional bench terraces were costly to construct, and were
not always well adapted to modern cultivation equipment. The modern
conservation bench terrace is adapted to slopes up to 6 - 8% and may
be changed to meet cultivation machinery needs. The conservation
bench terrace is commonly referred to as the zingg conservation bench
terrace (Fig. 2 Appendix B) which is designed for use in semi-arid
regions where maximum moisture conservation is needed. It consists
of an earthen embankment and a very flat channel that resembles a
level terrace (Schwab, 1966).
Bench terraces are the most ancient forms of conservation
structures and still common, on hillsides of heavily populated areas, in
many parts of the world. They are preferably constructed on steeper
30
hill slopes of 12 to 27% or more (Morgan, 1986) in a form of a series
of steps, which horizontal or nearly horizontal strips of earth and
almost vertical walls between the strips (Hudson, 1981). Bench
terraces can be constructed on slopes upto about 45 - 55% where the
soil is fairly deep (USDA, 1984).
The flat strips, which are supported with steep vegetated earth
banks, concrete, brick or loose rock walls (risers), are used for
cultivation and assisted in erosion control by decreasing the velocity
of run-off water and arresting the accompanied silt loads (FAO, 1989).
In areas of low rainfall back-sloping bench terraces are
constructed on the contour purposely to conserve all the rain that falls
(FAO, 1989). For rolling lands and hill slopes with inadequate soil
depth, graded or contour trenches are also used for forestation and
other plantation (Das, 1977).
c) Channel terraces
There are different types of channel terrace depending on soil
types, slope, climate and farming systems. Broad-base and narrowbased terraces are the most important of graded channel terraces
(Webster and Wilson, 1966). The former consists of a broad shallow
channel and a wide low bank, with gently sloping sides on its lower
sides 4 to 15 m wide or more. They are best suited for very gentle
slopes of 2 to 10 percent and large farms and can easily be crossed by
tractors (FAO, 1979). The latter type consists of a channel and a steepsided earth bank of 1.5 to 4 metres wide at the base and 0.3 to 0.6 m
31
high, built along the contour or on a slight grade. They are best suited
to steeper slopes than broad-base terraces (Roche, 1956).
Channel terraces consist of earth banks (bunds), formed on
downhill side, with associated shallow channels immediately above
them to impound rain water run-off, thus encouraging water
infiltration into the soil (Hudson, 1981). The shallow channels also
divert the excess run-off water, across the slope, to natural drains at
non-erosive velocities.
d) Absorption terraces
All types of conservation terraces could be levelled (level
terraces) or provided with a slight gradient (graded terraces) according
to physiographic and climatic conditions of the site. The graded
terraces are provided with slight side ways slope of about 1 - 2%
towards a drainage channel, to avoid the accumulation of run-off
water, destruction of the earth bunds and formation of erosion rills or
gullies (Brandjes et al. 1989). Drainage terraces are suited to areas
where the slope is between 3 - 10% and the permeability of the soil is
low (FAO, 1979).
The absorption terraces are level terraces built on the true
contour and are more desirable for areas where rainfall is low and
erratic, soil is absorptive and the slope is less than 6% (FAO, 1979).
They are usually closed at the end (closed-end terraces) to impound all
rainwater, (retention terraces), encourage infiltration and conserve
moisture as well as reduce soil erosion (Hudson, 1981). The bunds are
32
drained through controlled outlets only in case of heavy storms or
occasional flooding.
2.1.5.2 Run-off farming
It is used in Sudan e.g. water spreading in Kassala. The
harvesting of sheet flow run-off is a traditional technique practiced in
many parts of the Sudan where soil conditions permit. The technique
involves harvesting run-off water by low earth bunds called “Teras”
(Van, 1991).
2.1.5.3 Contour farming
The contour furrows or terraces break up the slope and cause
more of the soil to be splashed uphill (Schwab and Frevert, 1985),
thus reducing erosion losses by 50%, on slopes less than 10% as
compared to up-and-downhill operation. Also, through throwing the
furrow uphill, the downward movement of soil due to erosion can be
checked (Fitzpatrick et al., 1970).
Contour farming means ploughing and planting sideways across
the slope and along the contour. It includes formation of furrows,
25 - 35 cm deep and 2 m wide (Bensalem, 1977) or terraces every 30
to 40 m (USDA, 1984), as additional protection measures against
run-off and erosion by water and to increase the surface storage
capacity.
The present method of afforestation in the arid clay plains of
Kassala province is the conservation of rain water by retaining it on
the site by means of contour furrows (Heibloemm, 1985). If the
33
topography of the locality permits, the amount of water in the site may
be increased by leading water in channel from near-by flow areas
(Badi, 1965). This method was carried-out in Malawiya in 1965. The
seedlings were planted half way up on the side of the furrow to avoid
possible suffocation to the roots (Fig. 3 Appendix B). Before making
the furrow by tractor and ridger, the direction of the slope was
determined by sight (Badi, 1965). The furrows were made across the
direction of slope to follow approximately the line of the contour.
Some plants died in the higher parts of the furrows because some of
the furrows did not actually follow the contour and in fact helped to
drain the sites rather than conserve the water (Badi, 1965). It must be
pointed out that the determination of the direction of slope by sight is
extremely unreliable in these apparently flat plains (Badi, 1965). In
fact the portions of the site believed to be low were found to be high
and portion believed to be high were found to be low after contour
mapping (Brower, 1985). To achieve good results the direction of the
furrow across the slope along the contour should be determined by
proper contour surveying (Heibloemm, 1985). According to Badi
(1985) there is one more interesting point to mention about the
contour furrows that before making the furrows in the areas intended
for afforestation, the tractor and ridger were tested by making four
furrows outside the forest. If the soil is solid heavy clay or “Gardud”
soil deep ploughing is important. The place of seedlings on the
furrows depends on the prevailing rainfall in the area (Badi, 1965). In
34
good rain areas the seedlings were planted half way up on the side of
the furrow. In poor rain areas the seedlings were planted at the bottom
of the furrow (FAO, 1976). In heavy clay soil the seedlings were
planted on the furrow crest to avoid possible suffocation caused by
retained water (FAO, 1976). According to Badi (1965) the possibility
for seedling to success is greater than seeds, and seedlings should be
planted early in the rainy season while seeds should be placed before
rainy season.
2.1.5.4 Ridging and tie-ridging
The ridges serve as effective construction measures especially
when laid out across the slope on the contour. The furrows are graded
to discharge the excess water into grassed waterways. Ridging is one
of the most popular and widely used methods of land preparation
through which a loose and friable seedbed is produced in surface soil
for planting or seeding crops (Kowal and Stockinger, 1973).
Tied ridges are open ridges to which short earthen dikes (ties or
barriers) are constructed, at right angles, at intervals of 1-2 m
(Hulugalle et al., 1990). The ties join the adjacent ridges and form a
series of microbasins (furrow-bassins) which fill with water during
rain. They have the same height as the ridges.
Different studies (Pereira et al., 1967; Understander, 1986;
Hulugalle and Rodrigues, 1988) proved that tie-ridging systems were
effective water-conserving measures for improved crop yields. They
attributed crop yield increases primarily to reduced water runoff and
35
consequently greater soil water storage during the growing season, as
compared to flat planting or open ridging. Furthermore, tie-ridging
may be required to minimize waterlogging stress during frequent or
heavy rainfall (Efron, 1988). Labour constraints, difficulty of
construction and requirement of supporting practices, on steep slopes
and in case of intense storms, have contributed to the poor adoption of
this practice by the farmers.
2.1.5.5 Micro-catchment technique
Which have smaller catchment areas than conservation bench
terraces, but the percentage run-off is generally higher (Allred, 1962).
Micro-catchment system is often constructed in series (Fig. 4
Appendix B) which proved to be very successful for establishing trees
under semi-arid conditions. Micro-catchment size ranges from 16 m2
to 1000 m2 depending on rainfall. This type can be used where
extremely rough terrain exists. Some micro-catchment systems are
adopted in experiments of Arabic gum belt in Kordofan (Fig. 5
Appendix B). The soil is loosened by tractor, and the types used are:
Sloping catchment 1 m slope (1 in 3 m) on both sides with and
without a trench, trenches with 0.3 m width and 0.3 m depth, pits with
0.5 m diameter and planting on flat ground (control). The sloping
catchment without a trench proved to be the best system (with Acacia
albida averaging 155 cm after 1½ year on 180-200 mm average
annual rainfall), followed by sloping catchment with a trench and
trench only. Growth was poorest on flat ground (Sheikh et al., 1984).
36
According to Chopart (1979) in control plots the crop was stunted and
show symptom of water and nutrients deficiency because of high
surface soil bulk density, low porosity, impeded infiltration and low
water holding capacity of the soil. Perrier (1986) mentioned that
during the seasons with poor precipitation improved seedbed
conserved more soil water relative to the traditional seedbed where the
soil moisture fell below the wilting point at about 70 and 86 days after
sowing. According to FAO (1976) micro-catchment is suitable for
sandy soils where they are easy to make and the following types can
be adopted:
a) Triangular or v-shaped conFiguration
Which is known as water-catchment (Fig. 6a Appendix B). The
idea of this techniques was introduced from Terkan in Kenya. It is
believed to be an Arabic technique adopted by ancient Arabs, and has
been used in Alain Central Forest Reserve with good results (Fig. 6b
Appendix B), that convinced the local neighbouring villager to use it
in fodder production and community forestry practices (Badi, 1965).
b) Deep planting
In which the root ball is placed within the moist subsoil (Fig. 7
Appendix B) below the desiccant surface soil considerably increases
amount of soil moisture immediately available to roots of young
plants (Proud, 1988).
2.1.6 Water harvesting in the Sudan
37
Mohamed (1994) has mentioned that the prerequisites for
successful water harvesting involve the following:1.
A minimum mean rainfall of 80 mm per rainy season, if the
rainy season coincides with the cold period of the year. More than
80 mm are required if the rainy season occurs during summer when
evaporation is high.
2.
Presence of impermeable soils on the catchment area.
3.
Soils in the cultivated parts with high water storage capacity in
order to ensure an ample moisture supply for the crops during
periods having no precipitation.
4.
No more than 2-3% salinity in the cultivated soils.
Furthermore Tauer and Humborg (1992) added that the
topographic and climatic condition must be appropriate for harvesting
rainwater and directing runoff to cultivated sites.
Several water harvesting techniques and agricultural practices
were and still practiced by the local farmers, on sloping lands and in
areas with variable and unreliable rainfall, to reduce the risk of crop
failure. Farmers adopted bench-terracing systems, for many thousands
years, the signs of which are still found in hilly areas such as Jebel
Marrah (HTS, 1958). Spore (1997) noted that “water harvesting was
developed by the ancient Nabateans over 3000 years ago in what are
today called Israel and Jordan, and it is probably not a coincidence
that very similar techniques have been developed and have survived in
38
the Red Sea Hills of North-East Sudan and in the Central Darfur
region”.
In Sudan, on plains to the east of the Nile where there are large
areas of clay soil and gentle slopes, embankments are made to
intercept sheet-wash runoff following heavy storms. Quick maturing
millet is planted immediately after the water which was left by the
storm has subsided. ‘The crop grows and matures in 80 days, using the
moisture that has been induced to infiltrate in the soil behind the
bunds’ (Wickens and White, 1978). According to Kutsch (1982), plots
cultivated like this are known as teras. He describes them as artificial
basins used for cropping on slightly sloping land. The technique
conforms with the definition of rainwater collection. In that the water
is sheet flow (not channel flow) on the short and gentle slopes of the
Sudan plains.
Draw-down cropping (i.e planting on river banks following
falling water levels) had been and is still practiced and locally known
as Geroof cultivation in Northern Sudan. Water spreading, which is an
ancient method of irrigation, is practised in small and large scale farm
in western and eastern Sudan. It is a technique in which flood water is
diverted from a stream channel and allowed to flood over an adjacent
land surface. Delta Tokar in eastern Sudan, Khur Abu Habil in
Kordofan, Wadaa and Kuma projects in northern Darfur are good
examples (Mohamed, 1994).
39
Earth bunding (Teras Earthen bunds-singular teras, plural terus)
systems are found in most parts of the Sudan, particularly in areas
with clay soils and 100-400 mm rainfall. In Kassala region, eastern
Sudan, earth embankments (terus) are constructed to intercept sheetwash runoff, from adjacent catchments, following heavy storms
(VanDijk and Ahmed, 1993), thus harvesting nutrients and controlling
erosion (FAO, 1994).
Limited research work has been carried out on the rainwater
harvesting techniques for agricultural purposes in the Sudan.
Mulching and intercropping are practiced in small scale farms,
mainly to modify the microclimate. Positive results were obtained
especially for horticultural crop production (Abdel-Hafeez, 1976).
Salih and Ageeb (1983) studied the effect of irrigation regime
and mulching on yield of Faba beans at Shambat and Wad Medani.
They found that grass straw mulch at Wad Medani and groundnut
shells at Shambat increased the grain yield by 21% and 15% over the
unmulched crop, respectively.
Riley (1985) reported that ploughing effectively increases water
intake of ‘Gardud’, whereas ridges and furrows trap surface runoff.
Studying the effects of four tillage systems and contour bunding
on “gardud” soil physical properties, water storage and sorghum plant
growth and yield. Omer and Elamin (1997) found that chisel and 10 m
contour bunds resulted in improved soil physical properties, soil
moisture storage and crop yield as compared to other tillage systems.
40
2.1.7 Water harvesting in Arab states
According to Ibrahim (1992), assessment of annual rainfall in
water resources is 2282 billion m3 which is equal 160 mm per annum
(Table 1 Appendix B). From this amount approximately 136 billion
m3 runs as rivers, permanent resources and feeds under ground water
in terms of seasonal drainage of natural channels and part of this water
is intercepted and stored for irrigation. Due to the increase of water
demand specialists and agricultural engineers are compelled to use
more advanced methods in order to maximize the usage of water as a
new potential source and consequently increase the production in arid
and semi-arid zones (Perrier and Sulkini, 1997). One of these methods
is water management techniques which is known as water harvesting
(Yahyia, 1997). According to Khuri and Duri (1986) methods used in
water harvesting are: Construction of small retention dams, soil
treatment to minimize permeability, soil cover with impermeable
layer, establishment of paved passages, building of walls to collect
water, change of plantation cover, improve soil physical properties to
improve permeability for deeper percolation which enables the plants
to absorb water and in some areas soil treated to increase rate of
infiltration to charge under ground water. Approximately 1136 billion
m3 from that mentioned 2282 billion m3 supported under ground
water, increase soil moisture content, enhance plants growth or runs as
seasonal natural channels (Perrier and Sulkini, 1997). 161 billion m3
41
runs to seas and oceans surrounding Arab States (Jan, et al. 1986; Jan
and Douri, 1990).
The most adopted method of water harvesting in the Arab States
is rain run-off from sloping hills and mountains intercepted by dikes
(50 cm height) and held on cultivated area until it evaporates or
infiltrates then the soil becomes more fertilized due to silty soil carried
by rain run-off so the soil can be prepared for cultivation (Yahyia,
1992).
Another adopted method is the depressed areas that are flooded
or likely to be flooded. These areas are believed to be old rivers or
channels beds. These shallow depressions contain depositions of silt
that was carried by water running-off. Most of the flood water comes
from rivers through the natural canals that link the basins with the
river. Walls built at the canal Junction with the river has been found
effective in controlling undesirable flooding. Then plantation begins at
the edges of the flooded areas as water recedes (Yahyia, 1992).
In Lebanon and part of Saryia, rain water is collected to irrigate
crops grown in green houses and glass houses. Water is usually stored
in tanks (200-400 m3) to be used in drip irrigation system. In some
areas large lakes are constructed at the bottom of slopes and covered
with impermeable materials. The capacity of these lakes is about
50000-70000 m3 which can be used for irrigation of fruit trees and
vegetables (Khuri, 1986).
42
In Jordan water harvesting is considered as a secondary option,
but it is adopted in some areas in different methods. One of these
methods is the construction of large basins to collect water for
irrigation. Other types are bench terraces, contour furrows trenches
canals and basins surrounded by stony walls (Duri, 1986).
In Yemen, flood water is the main type of water harvesting. The
rain run-off is intercepted at vallies by means of earthen dikes 10 cm
high, which are used in Tohama region. At the southern part, steps and
graded terraces are adopted. The main problems of water harvesting in
Yemen are: Soil erosion and the limited quantity of rain water, so the
continuous proper maintenance of water harvesting structures is an
essential point (Hazzouri, 1995).
Sultante of Oman is the best example to show the importance of
water harvesting project where several small retention dams are
constructed to collect and store water which is used by the inhabitants,
for drinking and irrigation. In areas of moderate height traditional
harvesting methods are applied (Hazzouri, 1995).
In Libya, suffers from water shortage in the desert area. In the
areas north of Al Jabal Al Akhdar the annual rainfall is about 200 mm
and water is harvested by traditional methods that are adopted since
the Roman Empire. Basins for water collection and contour furrows
are used by inhabitants to irrigate small cultivated areas. Also in some
areas small retention dams at the bottom of the slopes are used to
43
irrigate fruit trees. Poor management and maintenance led to soil
erosion which decreased the production (Schmid and Batashi, 1995).
2.1.8 Limitations of water harvesting
According to Ibrahim (1992) the limitations of water harvesting
are: Availability of natural or constructed canals to convey water,
availability of natural or constructed reservoirs to store water,
construction of terraces and dams to store water, availability of soil
of low permeability or usage of some techniques to lower the
permeability, continuous silt elimination from reservoirs to keep them
at constant capacity, properly stored clear water i.e. free from
contaminants, the effect of reservoir on site ecology that the reservoir
is considered as good medium for insects generation, and evaporation
control.
Inspite of the above mentioned limitations water harvesting
system is used in arid and semi-arid regions because it is considered as
a cheap and a simple method compared to other methods such as deep
ground water pumps, and pipes to convey water from surface
resources to distant sites, so the water harvesting projects need careful
studies before the beginning of the construction such as:
i-
Site hydrological characters in term of rainfall and runoff quantities as well as ponds that retain rain water.
ii-
Soil surface nature in term of slope, topography and soil
permeability.
44
iii-
Studying
the
natural
reservoirs
and
embankment
distribution or constructing new dams and embankments.
iv-
Best method of evaporation control.
v-
It is important to protect reservoirs from erosion, run-off
and sedimentation.
vi-
The economic feasibility to construct water harvesting
utility in term of capacity of reservoirs, to what extend the
utility might be in promoting the cultivation and how to provide
water for domestic uses to minimize the residents migration
from arid or semi-arid areas.
vii-
The necessity to develop local skilled technicians to
manage the water harvesting projects (Yahyia, 1992).
2.1.9 Water harvesting in some world countries
A lot of countries in arid and semi-arid regions adopted water
harvesting techniques to irrigate crops.
In Mexico which is characterized by more advanced water
harvesting techniques, depressed areas and passages are paved to
increase the quantity of run-off water, to inhibit weeds growth and to
decrease infiltration. For the same purposes plastic film mulches and
scrapped plastic tyres mixed with asphalt are used in some areas also
paraffin wax is used to decrease soil permeability (Hazzouri, 1995).
In Australia, where there are advanced water harvesting
techniques, salt is used in most arid regions which is mixed with the
upper soil surface to destroy clods and particles then impermeable soil
45
skin, weeds control, and unpolluted soil are obtained (Dutt and
Macreey, 1974).
In some other areas straw mixed with soil is used to decrease
infiltration rate and increase sheet flow run-off to be collected in
reservoirs in addition to the mentioned plastic film to cover the
surface (Dutt and Macreey, 1974).
In arid regions wind break are use around the depressed areas to
decrease evaporation and water surface is also covered with small
pieces of sponge for the same reason (Dutt and Marcreey, 1974).
The technique of rain water storage is adopted in areas that are
geologically characterized by high capacity, high storage ability and
permeable soils. The simplest ways to provide drinking water is by
roof water harvesting method, then this water is boiled and treated to
be used by residents (White, 1974).
2.2 Acacia nilotica tree (vernacular: Sunt)
2.2.1 Location and Boundaries
The Sunt reverine forests lie along both banks of Blue Nile
as detached areas (Fig. 8 Appendix B) . At the northern limit, south of
Khartoum (Lat. 15o 36` N. Long. 32o 31` E.) in the north (Fig. 8a
Appendix B), and Rosaries (Lat. 11o 50` N., Long. 34o 31` E.) in the
south Fig. 8b Appendix B (Booth, 1949). None of these two
boundaries is natural limit to the growth of Sunt. Acacia nilotica is
found both south and north of these boundaries (Booth, 1949 and
Jackson, 1959).
46
2.2.1.1 Configuration and floods
The topography of the tract (terrain) is generally flat, featureless
clay plain with a gentle slope from south to north. From 438 metres
above sea level at Rosaries to 184 metres at Rufaa. The distance
between these is 638 kilometres. The channel of the Blue Nile is very
deep, thus giving rise to steep slope between the edge of the clay plain
and the river bed (Booth, 1949 and Jackson, 1959).
The unique feature of the topography of the flood basins of the
Blue Nile has been created by the meandering action of the Blue Nile.
The mechanism involves erosion action on one bank and deposition of
sand and silt on the opposite bank of the river bends (Foggie, 1968).
Although this process is slow, it is believed to be continuous, cutting
off alternating channels and creating a new river course. The cut-off
channels are linked to the new river by narrow canals which become
shallow due to the continuous deposition of sand and silt (Foggie,
1968).
The existing flood basins of Blue Nile, which now bear Sunt
forests, are believed to have been created by this meandering activity
of the river course (Jackson, 1959). The topographic features of these
basins are common to all and described a typical flood basin. The
bottom of the basin, the old river bed, is locally known as “maya”
which means a shallow depression often flooded. The basin slopes
nearest to the present river are locally known as “gerf” and the slopes
adjoining the clay plains inland as “Karab slope” (Jackson, 1959).
The Blue Nile level starts to rise in May at the onset of the rainy
season on the Abyssinian plateau in Ethiopia. The level reaches its
peak in August, which almost coincides with the time that the monthly
rainfall peak is reached. The maximum level is then maintained during
August and starts falling from the beginning of September until it
reaches its minimum in early May (Booth, 1949). Except for
exceptional years, the level rises within a range of 8-13 metres
between May and August. Flooding of basins follows the trend of the
river. The high levels of the “gerf” and “Karab” upper slopes are
flooded only during period of exceptionally high floods when the river
level rises by more than 13 metres and for very short periods. The
lower slopes of the basins, however, are usually flooded for 1-3
months during July – September when the river levels peak. The
“Maya” on the other hand are usually flooded for longer periods
specially in basins nearer to Sennar Dam (Booth, 1949).
Most of the flood water comes from the river through the
natural canals that link the basin with the river. Small amount of the
47
basin floods comes from water run-off from inland (Jackson, 1959).
The basins are generally flatter in the northern part of the area. In the
southern part the basins are better defined and deep. The floor of the
northern basins are very uneven due to the ramification of numerous,
shallow channels which frequently originate as gullies on the eroded
Karab slopes (ElSiddig, 1985).
2.2.1.2 Soil
The underlying geological formation of the whole area is the
Nubian series. The soil of these plains is referred to as “cracking
clays” a term that describes the cracking nature of the soil during the
hot dry weather. The whole of the clay plain surface, except for the
trough and grooves of the Blue Nile, is covered with mantle of
“alluvial” hydromorph clay (Yahia, 1973). The clay layer is believed
to have been brought by the Blue Nile, during the past pluvial period
or since about 50,000 B.C., from Abyssinian high floods. The upper
most clay bed may be from 6-10 metres in the depth overlying
alternating layers of sandy and silt alluvial beds (Yahia, 1973).
Evidence of the underlying alluvial beds has been drawn from deep
water wells near settlement areas. During the rainy season, the clay
soil absorbs water, swells and closes the cracks, when saturated the
clay becomes impermeable and most of the surface water is drained
by run-off (Yahia, 1973).
The soil texture is fine, the alkalinity is high and there is
relatively poor leaching by surface water. The general soil type is the
dark cotton clay soil “vertisols”. Basins are of two types, depending
on whether they represent the final stage in the upbuilding of a typical
silt deposit or the last stage in filling of a lagoon (Harrison and
Jackson, 1958). The Blue Nile basins are of the latter type. The soil of
the flood basins of the Blue Nile exhibit same variations from that of
the clay plains (Harrison and Jackson, 1958). According to Jackson
(1959) here the soils may be classified into three major soil groups
related to the basin topographic classes.
a) Maya
The dominant soil of the “Maya” is typical of the dark, heavy,
alkaline, cracking clay believed to have been brought from the clay
plains by water run-off. The soils of the basins are recent, immature
alluvial deposits, young soils (Entisols), which although bedded, have
no recognizable A and B horizons. They are called montmorillontic
clay which have the property of swelling when moistened and
contracting when dry to form cracks up to one meter deep.
48
b) Karab
The inland side of many basins is eroded slopes (vernacular:
Karab), characterized by considerable accumulation of CaCO3
concentration and a higher content of silt, sand and gravel exposed as
a result of erosion. They are more permeable than clay and may have
more moisture at deeper levels.
c) Gerf
According to Jackson (1959) on the river side of some of basins
there is a deposit of rich alluvial soil (vernacular: gerf) have deep,
permeable silt deposit loamy with good drainage and free aeration
known to be the most fertile type of soils but there is excessive weed
growth. Tothill (1948) described the gerf soils as alluvial pockets of
very rich soil capable of producing very high yields. It is mainly sand
and silt with a small proportion of clay. These soils are suitable for
trees growth (Jackson, 1959).
The clay plain soils and the flood basins have been influenced
mainly by weather factors. In the northern basins the combination of
drier climate and blown sand and dust cannot fail to have a marked
effect on soil properties. The deep underlying geological rocks of the
ancient basement complex had no effect on their formation (Bunting
and Lea, 1962; Foggie 1968).
2.2.1.3 Climate
The location of Sunt areas lies within the tropical hot semi-arid
climatic zone, with a summer rainy season of six months (May to
October) with a peak in August and dry season from November to
April (Sudan Meteorological Department, 1980). Mean annual rainfall
ranges from 500 – 800 mm, maximum temperature reaches 41.1oC in
April, a second peak of 37oC is reached in October (SMD, 1980).
With the onset of rain temperature falls to an average maximum
of 31.1oC during August. During December – January maximum
temperature is 36oC with a minimum of 15oC. The mean daily
minimum temperature is at its highest of 24-25oC, in June and its
lowest 13-14oC in January (Sudan Meteorological Department, 1980).
Generally the coldest month is January and the hottest month is April.
During the rainy season, the prevailing winds are from the south east
and during the dry season from the north east. The relative humidity
trend is influenced by temperature and rainfall, reaching its maximum
in August and minimum in April – May (SMD, 1980).
2.2.1.4 Vegetation
49
The natural vegetation of Sunt location area prior to the
establishment of the Sunt plantation can be described in relation to the
topographic classes and their soil groups. Man’s activities through
cultivation and plantation establishment may have modified the
vegetal succession of the area, a situation which makes it difficult to
describe the vegetation under closed canopies or area cleared for
agricultural purpose. However the type of vegetation found on the
area after final falling or under poorly stocked Sunt crops is observed
to have similar feature to the natural vegetation described in many
publication (Andrews 1948; Booth 1949; Smith 1949; Harrison and
Jackson, 1958).
The characteristic natural vegetation type on the northern clay
plains is Acacia – Balanytes, Savannah woodland associated with
thorny bushes, scrub and annual fall and short grasses (Harrison and
Jackson, 1958). Annual grass fires and grazing are among the many
factors that contributed to the disturbance of the vegetal development
of this area. However, the clearance of the land for cultivation and fuel
wood production are the dominant factors in the destruction,
approximately 37,000 acres annually (Yahyia, 1973).
Because of the extremely limited capacity of the clay soils for
available water, the occurrence of Sunt on the clay plains is sporadic
and confined to small catchment areas or narrow water courses
periodically flooded by rain water run-off. Sunt, however attains its
best development in the flood basins of the Blue Nile and its
tributaries in pure stands or mixture. The natural forest types and the
associated vegetation on these basins vary on the different topographic
classes (Yahyia, 1973).
a) Karab slopes
A mixture of Acacia including Sunt constitutes the forest type
of the rarely flooded upper slopes. The proportion of Sunt increases
down the lower slopes towards the “Maya” and decreases towards the
clay plains. According to Andrews (1948) the associated vegetation
includes Cyprus species on the lower slope and Punicum and Aristeda
species on the upper slope where Acacia nilotica gives way to less
moisture demanding species which may occur in pure or in mixture.
These species are Acacia seyal, Gregarious species, Balanites
aegyptiaca (Higlig), some Acacia mellifera (kitir), Gregarious
colonizer of recently cleared land and Acacia nubica (laot). Other
Acacia like the gum Arabic tree, Acacia senegal (hashab) occurs in
small numbers in the southern part where rainfall is higher. The Karab
50
areas, however, in many instances lies bare of vegetation mainly due
to over grazing and perhaps also petty thefts (Yahyia, 1973).
b) Gerf
A hoard of shrubby species found in or adjoining Karab forest,
particularly on the “gerf” side. The number and frequency of
occurrence of these species is noticed to decrease from south to north
following the decreases in rain (Andrew, 1948). The upper slope bear
a mixture of species dominated by Sunt. The associated species as:
Ziziphus spinachristi (sidir), Mytenus senegalensis (yoi), Capparis
deicidua (tundub), C. tomentosa (heikabit), Cordial africana and
Cordia rothii (indrab), Salvadora perrica (arak, shao), Indigofera sp.
(dahasir), Crataeva adansonii (dabkar), Ficus sp. And Boscia
angustifolia (surreih). Tamarix aphylla (Andrews, 1948). While the
lower slopes are characterized by pure Sunt. The associated ground
flora include Punicum sp., Cassia sp. and Beckoropsis sp. (Andrews,
1948).
The vegetation in Sunt basins as the name implies is pure
Acacia nilotica in the major part. Other species such as Acacia seyal
(talh), Acacia sieberana (kok), Acacia albida (haraz), and Tamarix
orientalis (tarfa) occur to varying extends, normally fringing the pure
Sunt stands and sometime in admixture on the moist gref-side.
c) Maya
According to Yahyia (1973) on the “maya” where prolonged
flooding often occurs, the ground flora is absent except for a sparse
cover of a prickly-leaved mixture of herbs known collectively as
“terma”. “Maya” flooded for over six months are almost bare of tree
cover. The only species found as a scattered trees is Sunt. “Maya”
flooded for a period up to six months carry pure Sunt stands. However
there are few “maya” that may be flooded for optimum period of 3-5
months where better growth of Sunt is observed and the “terma” cover
becomes denser (Table 2 Appendix B).
2.2.1.5 Grasses and herbs
According to Yahyia (1973) the grasses and herbs in basins are
various and numerous as:
a)
The annual Aristida sp. (humra, deil elfar), Schoenfelia gracillis
(danab elnaga), and Eragrotic sp. (banu) are found on the drier
sites in some of the northern zones.
51
b)
The perennial sedge, Cyprus rotundas (seid) a noxious weed is
wide spread in the moist part of the forest and its rhizomes
constitute an important food item to wild boars, Sorghum sp. (adar)
is found in the southern basins with higher rainfall (Yahyia, 1973).
c)
Other species that can be mentioned are the herbs Cassia senna
(sanamakka) which is grazed with relish when dry, and Solanum
nigrum (gibbein) which occur at the fringe of the forest particularly
on the “karab” side (Elsiddig, 1985).
2.2.2 Afforestation and silvicutural treatments
2.2.2.1 Botany description (leafing, flowering, fruiting and seeds)
Acacia nilotica as described by ElAmin (1973) a tree usually
2.5-15 m high sometimes as low as 1-2 or up to 25 m. Bark or trunk
rough and fissured, black to blackish grey or brown, never powder or
peeling. Young branchlets brown, grey or pink, glabrous to pubescent.
Crown variable in outline, in Africa flattened or rounded and
spreading, in India and west Pakistan varying to hemispherical or
narrow and erect. Spines white, paired, mostly 1-8 (very rarely to 13)
cm long. Straight enlarged or inflated, often deflexed. Petiole
glandular with (1-2) glands, 1.3 cm long. Rachis tomentose up to 6 cm
long, glandular at end 1-3 pinnae grooved adaxially. Pinnae 3-9 pairs,
2.5-3 cm long leaves 2-7 cm long leaflets mostly in 12-27 pairs per
pinnae, rarely as few as 7 or as many as 36, glabrous to pubescent,
1.5-7 mm long, 0.5-1.5 mm wide, margin ciliolate, apex acute to
mucronate. Inflorescent in globose head, yellow, peduncle pubescent
1.5-3 cm long, involved on upper part of peduncle, subtending 1-3
flower, floral brack pubescent 1.5 x 0.3 mm. Flowers sessile, bright or
golden yellow, sweetly scented in round fluffy heads 6-15 mm in
diameter, on axially peduncle 1.2-4.5 cm long, bisexual and male
flower in the same inflorescence. Clayx 4-6 lobed, pubescent darker
than petal, 1.5 x 0.6 mm. Corolla 4-6 lobed, pubescent, yellow,
2.5x0.8 mm. Anther free, glandular, 5.5-6 mm long, ovary brown
glabrous 0.9 mm long, style 5.5 mm long stipe 0.2 mm long (El Amin,
1973). Pods variable necklaced or not margins crenate or nearly entire
dehiscent, straight or lightly falcate, glabrous to pubescent, dark
brown to dark grey, 5-20x1-2 cm, surface ridged, venation
longitudinal or not apparent, 10-12 seeds to the pod (Andrews, 1952).
52
The seed has a very tough apparently water proof testa: Seeds dark
brown or brownish-black, elliptic to subcircular 8 mm areole
marginal, U-shaped or closed O-Shaped, finical thin, brown, 3 mm
long, seeds lie longitudinally, obliquely or horizontally inside pods.
Flowering July – September, fruiting March – May. On dry sites on
heavy clays Sunt sheds its leaves soon after the rains have stopped or
flood water has receded. On favourable site rains its leaves much
longer and in some places it is ever green (Andrews, 1952).
2.2.2.2 Species
Acacia nilotica is generally accepted as a single, natural though
exceedingly variable species. It is at present divisible into nine
subspecies (FAO, 1982). Subspecies nilotica (Bereave, 1957).
Subspecies cupressiforms (Ali and Farugi, 1969). Subspecies
adstringens (Schumach, Thonn and Roberty, 1948). Subspecies
leiocarpa (Brenan, 1957). Subspecies kraussiana (Benth; Brenan,
1957). Subspecies indica (Benth, 1942). Subspecies tomentosa (Benth,
Brenan, 1957). Subspecies subalata (Vatke Brenan, 1957). Subspecies
hemispherica (Ali and Farugi, 1969).
2.2.2.3 Distribution
The species as a whole is widely distributed in subtropical and
tropical Africa (Fig. 9 Appendix B) from Egypt and Mauritania
southward to south Africa and in Asia eastward to India. Acacia
nilotica is occasionally cultivated elsewhere (Brenan, 1983). In
Sudan Acacia nilotica occurs naturally along Nile rivers and their
affluents in narrow interrupted strips (Fig. 8a Appendix B), the
natural occurrence of such strips is very meagre south of Jebelain. It
is, however raised successfully in a number of central Forest Reserve
in upper Nile as far south as Tawifikia some 12 miles south of
Malakal (Yahyia, 1982).
According to El Amin (1973) subspecies nilotica is mainly
found along the white Nile while subspecies tomentosa is mainly
found along the Blue Nile. Acacia nilotica is characteristic of hot dry
regions but does not thrive under less than 400 mm unless irrigated. It
can stand flooding up to 6 months and seedling can stand total
submersion for several weeks. It can also grow on heavy clay soil if
not too dry or water logged but growth is checked in saline soils
53
(Booth, 1949). On the “maya” and the lower slopes of the “gerf” and
“karab” of the flood basins which are seasonally flooded, Sunt forms
pure stands and no other species is ever found to compete with it
(Booth, 1969). On the upper slopes of the “gerf” though rarely
flooded, the available moisture is enough to maintain the species
growth provided that competition with other species like Zizyphus
spinachrist and Tamarix aphylla is eliminated (Foggie, 1968).
2.2.2.4 Light relationship
Sunt is a strong light demander, and will not grow even under
light shade, branchy when it grows single or in open stands. It is an
indigenous species to the region, and under favourable conditions
regenerates freely or naturally and more successfully in the flood
basins, than any other species so that there is no quest of species
choice for these sites (Booth, 1966). Knowledge of these ecological
characteristic of Sunt has been useful in the afforestation techniques
used for its plantation establishment on these sites (Booth, 1966).
2.2.2.5 Regeneration (Natural and Artificial)
The natural regeneration, however, is not enough to restock cut
over coupe areas. This is because many adverse conditions affect the
young seedlings such as:(a)
Flooding: Flooding is an important factor in the regeneration
and subsequent development of Sunt forest, affect regeneration
through water logging when it is prolonged (Yahyia, 1973).
(b)
Browsing Animals: According to Yahyia (1973) browsing
animals which shortly after the rainy season find nothing to
browse in the vicinity turns to forests, and stock like sheep and
cattle which are normally grazier turn into browsers and live on
the forests.
(c)
The deep and far reaching cracks in the clay soil. Which
developed during the summer, rupture the roots of the young
seedling and expose them to the hot, desiccating winds thus much
of the regeneration is killed (Yahyia, 1973).
54
All the plantation of the location have been established
artificially by either pit sowing at 2 x 2 metres (wider sowing distance
produce a branchy coarse crops) or broad-casting of seeds (Wunder,
1966). For the seed to germinate, prolonged submersion in water may
be necessary. Else, it is treated with concentrated sulphuric acid which
partially consumes the leathery testa and renders it absorptive to water
and capable of germination (Wunder, 1966).
In general pit sowing is the standard establishment technique on
the upper slopes of the “gerf” and “karab” which are flooded for short
periods. Shallow pits are made at spacing of 2 metres by 2 metres with
native hoes (Toria), and six seeds sown per pit. The seed is lightly
covered with fine soil after sowing 6 pounds of seed per feddan are
needed in pit sowing (2.7 kg per feddan = 6 kg per hectare) (Wunder,
1966).
Seed broad casting on the other hand is the standard practice on
the regularly flooded: “maya” and the lower slopes of the basin. On
sites where pit sowing is practiced, advantage is sometimes taken of
the taungya system to reduce the weeding and establishment cost.
These two techniques constitute the main methods of plantation
establishment (Yahyia, 1973). It is difficult to transplant Sunt, and
sowing is cheap and effective. Broadcasting require 30 pounds of seed
per feddan (13.5 kg per feddan = 30 kg/hectare) (Wunder, 1966).
2.2.2.6 Root system
The seedling rapidly develops a strong tap-root and naturally
this tap-root penetrates to considerable depths. A depth of 100 ft (30
metres) has been recorded in India. From the tap-root lateral roots
develop, which often also then produce sinker roots, which again
penetrate deeply (Badi, 1965).
2.2.2.7 Tending
Tending operation is done around the 6th year before thinning
commences. Sunt is susceptible to weed and grass competition and
thorough weeding is necessary in the first two year, especially on
“gerf” lands and land infested with “addar” grass (Sorghum sp.). The
most economical way of doing tending is to grow a field crop, such as
maize, with the Sunt. The maize must not be sown so thickly as to cast
excessive shade over the Sunt (Smith, 1962).
2.2.2.8 Beating-up
Beating-up by resowing blanks may be necessary in the year of
establishment and the variation in amount of flooding may necessitate
55
two or three re-sowings. Beating-up in the second and subsequent
years should only be done where there are large gaps in crops, and
blank caused by the death of one or two seedlings in the rows should
be left (Smith, 1962).
2.2.2.9 Thinning
However, the thinning intensity, the final stocking and the
rotation age have been a subject of continuous discussion and trials.
Earlier thinning prescription attempted by Booth (1949), Jackson
(1959), Deveer (1961) did not include numerical guides except for the
final crop where an average of 50-60 trees per feddan were to be
retained (Ahmed, 1976). The thinning prescription of Booth (1949)
was a summary of a general thinning programme as it appeared in his
statement “the continuation of thinning begun in 1947/48 in immature
Sunt leaving trees which would produce sleeper logs before the forest
is cut”. Jackson (1959) recommended heavy thinning for the first three
thinnings during the period of rapid height growth, and light thinning
for the rest of the time. In South Africa Craib’s (1939) reported that
numerical thinning gave good result in Acacia mollissima (Wattle)
and Pinus patula plantations where wide escapement and early
thinning were adopted. Smith (1962) advocated mathematical
approaches as being more objective than other type of thinning. The
first numerical guide to thinning practice in Sunt stands was made
by Foggie (1968) based on the provisional yield tables for Sunt by
Khan (1964). Ahmed (1976) summarized the quantitative guide of the
yield tables and outlined the method of their application. Thinnings
subsequent to the first thinning are mainly low thinnings aiming at
promoting plus trees. Suppressed or dying trees can be left since they
do not harm the favoured individuals. Larson (1982) argued that in
both even-aged and non even-aged forest, the largest trees continue to
grow faster than the smaller trees. Suppressed and dying trees are only
felled if they are merchantable or posing a hygiene hazard. Otherwise
they are left to fill the lower canopy. The first thinning should not be
left too long because many of the stem will be too drawn out or so
suppressed that they cannot quickly recover. Delaying thinning delays
the age of maximum growth. More light is needed for higher
increment in later growth stages. But too heavy thinning may be
unprofitable (Stratmann, 1982). Zajaczkowski (1978) stated that over
thinning of older stands and under thinning of younger stands can
cause large losses in increment. Therefore, the best thinning intensity
should be sought. Heavy early thinning leads to the culmination of
56
current annual increment within the shortest possible time. Hiley
(1967) remarked that when plantations are heavily thinned, the trees
grow in girth more rapidly reaching the merchantable size at an earlier
age. Further more the length of the thinning cycle should be inversely
proportional to the rate of growth. It is shorter for light demanders
than shade bearers but long enough to ensure that the volume record is
worth while. Too long thinning intervals are not desirable since they
might lead to loss in gross volume production.
2.2.2.9.1 How the thinning technique is carried out?
With a native hoe the seedling is singled to one for pit-sown
seedlings and to spacing of 2 metres by 2 metres for broadcasting
and/or natural regeneration (Wunder, 1966).
a)
2.2.2.9.2 Why the thinning technique is carried out?
When the plant 25-30 ft (7.5 m) the canopy closed and height
growth becomes very rapid and there is intense competition within
the stands, some trees soon establish themselves as dominant, if the
forest is left unthinned rapidly suppress and kill out the remainder
(Ahmed, 1976).
b)
During this period also wolf trees cause great damage by
causing the other trees to bend away from their heavy crown,
beside this the deformed stems should be thinned out, an exception
can be made in areas difficult to regenerate where any thing that
can be grown is of value (Ahmed, 1976).
2.2.2.9.3 Where the thinning technique is carried out?
Acacia nilotica is a strong light demander, fast growing species
giving high yields on good sites (e.g. Fung) and respond for saw-log
production (timbers). The development of mean diameter depends on
the spaces obtained by the thinning. Principally with view to salvaging
the trees which would otherwise be suppressed and die. On the other
hand at a slow growing stand, destined to produce firewood only,
thinning is unnecessary (e.g. North of Sennar dam) (Booth, 1949).
2.2.2.9.4 When the thinning technique is carried out?
57
If the seed is sown at the beginning of the rainy season (July)
the plant will be about two feet in December. At this height the
thinning technique is carried out. Flooding conditions or late sowing
will postpone the operation but it should be completed before the next
rainy season after planting. To remove the wolf and deformed trees
the thinning operation begins at about six year. Due to the rapid
growth of Sunt, thinning operation should be carried out at frequent
intervals, not exceeding three years (Ahmed, 1976). In good quality
crops the period of most rapid height growth ends at about the twelfth
year, when the tree is about 60 feet (18 metres) high. After this height
the growth continue at a moderate rate until about the fifteenth year,
after that it becomes slow. Thus heavier thinning should be
concentrated between the 6th and 12th years when the trees should
approximately be at the final spacing of about 50 plants/feddan (110
plants/hectare) (Booth, 1949).
2.2.2.10 Rotation age
The definition of the rotation age has also been a controversial
subject, Booth (1949) recommended 35 years as the probable rotation
suitable for the production of the size expected to satisfy the
utilization for which the crop was managed. While Jackson (1959)
suggested that 30 years could be a suitable age. Foggie (1968) agreed
with Booth (1949) on a 35 years rotation age.
2.2.3 Injuries to which the crops are liable
Yahyia (1973) classified crop injuries as follows:2.2.3.1 Man
Illicit cutting for building poles and fuel wood is about the only
direct injuring incurred by man. However, these fellings are constantly
checked by forest guards and do not constitute a danger to forest crop.
Man may also cause injury to crop by allowing his animals into
regeneration area or by starting a fire willfully or through negligence
(Booth, 1949).
2.2.3.2 Animals
a) Domestic animals
Browsing domestic animals like goats and camels can be a
major cause of failure of regeneration. Enormous number of goats are
reared in all villages near the riverine forests especially on the east
bank beside the normal herds. As most of the areas outside the
reserves lie barren of vegetation, the goat herds live almost completely
58
on the forest, and do great harm to young regeneration (Yahyia, 1973).
The thorne fence erected by coupe contractors normally rot after the
first rainy season. These animals together with sheep and cattle also
do harm to young regeneration through trampling. Enormous amount
of pods are eaten from the forest floor by goats (camels pick them
from tree crown even when green) thus reducing the amount of seed
for supplementary natural regeneration (Booth, 1966).
Other damage done to regeneration by goats is the cutting of the
leader shoot, sometimes to ground level, and sometimes it is actually
uprooted. The result is a stunted, delayed growth and reduction in the
density of stocking, and failure of regeneration altogether in extreme
cases (Booth, 1966).
Grazing, however, is not without benefits to the forest. In forest
areas where the regeneration period has been passed, grazing by sheep
and cattle is beneficial in minimizing grass competition. Another
benefit drawn from goats is that the Sunt seed which passes through
their intestines gets treated with stomach juices and germinates easily
when passed to the forest floor. Damage done by goats out weight the
benefits (Yahyia, 1973).
b) Wild animals
These include hedge hog, Grey Monkey (Cerecopthecus
aethiops), baboons and rats. The hogs do not harm Sunt crops. Grey
monkey and baboons besides occasionally grubbing the germinating
Sunt seed do no damage. Rats girdle young seedlings at the root-collar
by gnawing the bark and thus kill regeneration (Latif, 1968).
2.2.3.3 Insects
Die-back disease is found north of Sennar it is caused by a
beetle from the Buprestidae called Shenoptera chalcichroa arenosa,
ob. (Peake, 1956). The disease seldom kills the tree, but its effect can
be gauged by the large reduction in yield when the infestation is
severe. The symptom of the disease is stag headedness when the
branches above the point of attack get killed. The disease has been
known for long; no measures have been taken to curb it as damage
seems to be tolerable (Peake, 1956).
2.2.3.4 Birds
Zarzur (Quelea quelea aethiopica) generally appear only in
Sennar range, where they do slight damage. When found in large
numbers may break the branches (Yahyia, 1973).
2.2.3.5 Plants
59
Seid grass (Cyperus rotendus) and Dis (Cyperus sp.) perennial
sedge dominate the area cleared and make regeneration difficult. Both
are killed by shade. Adar grass (Sorghum sp.) an annual grass which
forms dense clumps 5 ft high can be difficult to eradicate in
regeneration areas. It can be killed by flooding or shade when the trees
develop closed canopy which is obtained after 4 or 5 years on good
sites (Ahmed, 1976). Climbers and creepers are confined to Fung area
and do not constitute a danger to Sunt. But Sunt is liable to damage by
creepers particularly in its early life so regular creeper cutting is
necessary (Booth, 1949).
2.2.3.6 Fire
Occasionally, however, willful fire or a fire crossing the fireline
from the adjoining cultivation land may touch the forest, in which case
damage in regeneration areas or in very young pole stands may occur
(Jackson, 1959).
2.2.3.7 Wind
It is damage is not strong (Yahyia, 1973).
2.2.3.8 Thunder
During the rainy season is not of frequency occurrence (Booth,
1949).
2.2.4 Rate of Growth
According to Badi (1989) rate of growth varies enormously
with the soil and flooding conditions. First quality Sunt in the Fung
area reaches 96 ft (29 metres) in height with dominants 17.5 inches
(44 cm) in diameter at 24 year old. Whereas fifth quality trees of the
same age only attain 32 ft (9.6 metres) by 11 inches (28 cm) in
diameter.
2.2.5 Ownership and legal position
According to Booth (1949), the land of all the forest has been
acquired and registered under the land Acquisition and the land
settlement and Registration Ordinance, 1925. The forests have been
gazetted as Central Forest Reserves under the Central Forest
Ordinance, 1932. All rights were expropriate when the forests were
constituted as Central Reserves. These rights include hunting, fishing,
seed collection, grazing, cultivation and collection of minor forest
produce such as gum and honey. Rights of the way have been
60
registered across some forests for the prompt passage of the public
and their animals from village to watering-places. The land occupied
by such right of the way is excluded from the areas gazetted as Central
Reserves.
i-
2.2.6 Uses
According to Yahyia (1973) Acacia nilotica is the most
important plantation, indigenous species in central Sudan yielding:a) Timber
Timber of Acacia nilotica is hard and durable suitable for:Round wood: Mainly for construction, boat
building, agricultural implements fence post and withies
(falakab).
ii-
Fuel wood: Used in industry for brick
burning and bakeries and for domestic use as charcoal.
iii-
Sawn wood: This is needed for railways
sleepers, native beds and carpentry.
i-
The Sunt forest being managed on short rotation do not produce
big dimension of timber. Acacia nilotica yields high volumes of sawn
timber averaging 223 m3 per ha at 30-35 years is possible in “gerf”
and “karab” sites (Goda, 1987).
b) Other minor produce
Tan: Pods (garad) and bark.
ii-
Fodder: Pods and leaves provide good
fodder for domestic animals during the dry seasons
(Yahyia, 1973).
2.3 Acacia tortilis
One of the most important species in Africa is Acacia tortilis
. This species, with its various taxonomic forms, has a wide
distribution in the arid zones of the world occurring from Senegal
in the west, to Arabia in the east and from Palestine in the north
61
to South Africa in the south (Brenen, 1959; Halevy and Orshan,
1973). In the Sudan, according to Harrison and Jackson (1958),
the semi-desert vegetation with rainfall of 75-300 mm covers
190,000 square miles of which 72,000 square miles are covered by
Acacia tortilis, Maerua crassifolia, desert scrub. Thus the
vegetation type dominated by Acacia tortilis comprises 37.9% of
the Semi-desert Scrub Division.
In the Sudan the species was studied by Crowfoot (1928),
Sahni (1968) and El Amin (1976) and on worldwide basis by
Brenan (1959), Fahn (1974) and Anderson and Brenan (1974,
1975). These studies revealed that three subspecies are found in
the Sudan: Acacia tortilis subsp. raddiana, subsp. spirocarpa and
subsp. tortilis. Their vernacular names are ‘Seyal’ (Arabic),
‘Sammur’ (Arabic) and ‘Towar’ (Hadandawa) respectively. They
are not confused by the natives in the areas where the taxon with
its subspecies occurs. This usage is consistent with Brenan’s (1959)
division of the complex.
Acacia tortilis occurs on on-flow sites which receive drainage
water. On these sites, subspecies raddiana occurs along the
seasonal water-courses while subspecies spirocarpa occurs away
from them.
Smith (1949) discussing the distribution of tree species in
relation to rainfall and soil texture, showed the following sequence
62
of occurrence of species belonging to the genus Acacia in the
Sudan from north to south with increasing rainfall.
Acacia ehrenbergiana, A. nubica, A. tortilis, A. mellifera,
A.
fistula,
A.
senegal,
A.
seyal,
A.
drepanolobium,
A.
campylacantha, A. sieberiana, A. albida, A. hebecladoides and A.
abyssinica. Thus A. tortilis occurs mostly in the north.
According to Harrison and Jackson (1958), the tree species
occurring in association with A. tortilis is Maerua crassifolia
Forsk. In recent years this species has disappeard particularly in
areas where over-grazing is common. The ground flora associated
with A. tortilis has been described by Jackson and Harrison
(1958), Halwag (1962) and Obeid and Mahmoud (1971) and
constitutes mainly grass species of the genus Aristida but are
replaced by Schoenfelia gracillis Kunth - on clay soils. On sandy
soils under higher rainfall, grass species of the genus Cenchrus
becomes abundant.
A. tortilis is known to be deciduous like most of the trees in the
region where it occurs. Tadmore et al. (1962), who studied the
phenology of the species in Palestine, found that leaf-shedding occurs
in summer and is associated with moisture availability. Stocker (1970)
coined the term ‘rain-green’ to signify the association of leafing with
moisture in Mauritania. Crowfoot (1928) observed that flowering
branches are devoid of the long white thorn, and only the short curved
63
thorns occur. Halevy and Orshan (1973) reported partial defoliation
before flowering occurs in sub sp. raddiana.
Floral biology received no attention, though seed and seed
production were studied by Peak (1952), Lamprey et al. (1974),
Janzen (1976) and Southgate (1978). These studies concentrated on
the biology of the Bruchids, while Lamprey et al. (1974) on the
interaction between Acacia, bruchid seed beetles and large herbivores.
The pods of Acacia trees are popular with cattle, sheep, goats,
elephants and antelopes. Ridley (1930) observed the method by which
animals disperse the fruits and seeds and how by passing the seed
unharmed they become more fit for germination. Acacia tortilis pods
are important feed source during the dry season. Seed survived in
relation to animal ingestion had not been studied. In the same manner
the effect of supplementation of animal feed with lucerne has not been
investigated.
Seeds may remain on the surface or may be buried in the
ground. These form the ‘seed bank’ of the species. Of these the buried
seeds were found to be of great importance in increasing the plant
population. No previous data was available on the fate of the buried
seeds.
Man through his animals causes a lot of damage to the natural
vegetation. The effect of conservation on the vegetation in semi-desert
areas had been evaluated by Halwagy (1962a, 1962b). However, the
effect of protection on the species was not evaluated. When a
population of plants is protected, it survives and is then subjected to
regulation by the environment. Several authors have pointed to the
64
phases of the life cycle when regulation of numbers in a population
occurs and agents involved in regulation Watkinson and Harper
(1978).
Studies on population dynamics are many particularly
population flux and survivorship (Sarukchan and Harper, 1978);
Kushwaha et al. (1981). Except for the study of the effect of coppicing
on Acacia tortilis, Bosshard (1966).
Most of the Acacia species in the semi-desert indeed in the
savanna region in the Sudan, leaf during or just before the rains and
are thus described as ‘rain-green’. The only exception is Acacia
albida, which is described as ‘rain-deciduous’. Flowering, on the other
hand, takes place during or after the rains and the seeds ripen before
the on-set of the next rains, within this broad picture certain variations
occur.
The area on which radiana and spirocarpa species grow are
grossly disturbed by human interference. The pods, and eventually the
leaves of both subspecies, are shaken off trees by herds men to feed
goats using local ‘muhjam’ (a long stick with wooden hook at its end).
Further, the leaves of spirocarpa in Khartoum and the neighbouring
White Nile province, are sometimes attacked by the Acacia bag worm
Auchmophilla kordofansis Rebel. The larva of this psychid feeds on
the leaves, mostly at night, during the summer rains. After the rains
less and less feeding takes place and the larva pupates in the bag and
eventually develops into an adult (Thoraton, 1957).
CHAPTER THREE
MATERIALS AND METHODS
65
The experiment was conducted in season 2003/04 in three
different sites, under rainfed conditions, to study the effect of three
water harvesting techniques, on water conservation and plant growth.
3.1 The study area
3.1.1 Location
The experiment was carried out at the White Nile state (latitude
12o-13o58`N; longitude 31o-33o18`E) and the altitude is approximately
500 m above mean sea level (Fig. 3.1). The three sites on which the
experiment was conducted were:
a-
Abu Humra Forest, Eldueim circle: It is situated in the west
bank of the White Nile (latitude 13o19` N, longitude 32o22.5` E)
138 km south of Khartoum. This site represents Northern White
Nile State.
b-
Elgazira Aba Forest, Kosti circle: It is situated in the east bank
of the White Nile (latitude 12o40` N, longitude 32o32` E), about
216 km south of Khartoum.
c-
Khur Kileikis Forest, Kosti circle: It is situated in the east bank
of the white Nile (latitude 12o25` N, longitude 32o35` E), about 250
km south of Khartoum. This site represents southern White Nile
state.
66
67
3.1.2 Geomorphology and soils
The study area is a gentle undulating plain. Isolated hills cover
some parts of the plain. The southern part is covered with a network of
seasonal streams flowing in the White Nile river. Parts of the state lies
in an area which is covered by the Nubian group (Nubian sand stone
formation), which is predominantly formed of sand stones and grits of
lower to upper cretaceous age (Whiteman, 1971).
The underlying geological formation of the whole area is the
Nubian series flowing from south to north. The White Nile river
traverses the vast clay plain. The soil of these plain is referred to as
“cracking clays” a term that describes the cracking nature of the soil
during the hot dry weather and excessive swelling when wet, also it is
characterized by low infiltration rates. The whole of the plain surface
is covered with mantle of “alluvial” hydromorph clay. The upper most
clay bed may be from 6-10 metres in depth overlying alternating
layers of sandy and silt alluvial beds. Evidence of the underlying
alluvial beds has been drawn from deep water wells near settlement
areas. During the rainy season, the clay soil absorb water, swells and
closes the cracks, when water saturated the clay it becomes
impermeable and most of the surface water is drained by run-off
(Yahyia, 1973).
The predominant topsoil at the southern parts is dark cotton clay
soil “vertisols”. At the northern parts the soil texture is fine, the
alkalinity is high and there is relatively poor leaching by surface
water. Scattered sedentary wide sand sheets (Goz) are present in the
west part of the White Nile.
68
3.1.3 Climate
The area of the experiment lies within the tropical hot semi-arid
zone. The climate is characterized by cold dry winters and hot rainy
summers “June to September” with a peak in August. The mean
annual rainfall ranges between 600 mm - 300 mm. Ten year mean
monthly rainfall distribution and the total annual rainfall in the study
area, for fifty years (1953-2002) shows the great variability of rainfall
(Table 1 Appendix A). It also shows that the climate of the study area
was wetter than at present. The rain generally falls as heavy thunderstorms with dry intervals between them.
The maximum temperature reaches 41.1oC in April, a second
peak of 30oC is reached in October. With the onset of rain temperature
falls to an average maximum of 31.1oC during August, because during
the rainy season the relative humidity is high. During DecemberJanuary period maximum temperatures are 36oC with a minimum of
15oC. The mean daily minimum temperature is at its highest 24-25oC,
in June and its lowest 13-14oC in January. Generally the coldest
month is January and the hottest month is April. During the rainy
season the prevailing winds are from the south east and during the dry
season from the north east, abundant sun-shine (average, 9.4 hours per
day), and a wide diurnal temperature range (minimum 17oC at night,
and maximum 46oC during the day). The relative humidity trend is
influenced by the temperature and rainfall, reaching its maximum in
August and minimum in April - May (SMD, 2000).
3.1.4 Landuse and vegetation
Agriculture has been practiced in the study area for centuries
and crop production is based on rainfall through various traditional
farming systems. Recently the irrigated schemes were practiced in
both sides of the White Nile. The northern part of the state lies in the
Acacia tortilis. Maerua crassifolia desert scrub type of vegetation
(Harrison and Jackson, 1958), where there is a sharp division into
hard-surfaced off-flow soils more or less completely bare of
vegetation, at one extreme and on-flow soils that have scrub bushes
and even some trees at the other extreme. At Abu Humra the
69
experiment was carried out on an off-flow soil and it contains a few
trees of raddiana near large khors and fine grooves of spirocarpa
away from khors. The associated Maerua crassifolia had been almost
wiped out by grazing animals.
The reserve lies near the village of Abu Humra and is roamed
by goats which are dominant and to a lesser extent by sheep which
browse and/or feed on pods of Acacia species during the long dry
season. Subsp. Spirocarpa is dominant in the reserve. The village
protect the bushes of spirocarpa and the few trees of raddiana from
felling by intruders as they form an important source of feed for their
animals. However, they occasionally, practice selective felling of one
or two stems of spirocarpa which is multi-stemed for their own use
and to sell in neighbouring Eldueim.
3.2 Layout of experimental field
The randomized block design (R.B.D) was selected. At each of
the three sites the soil type and slope gradients of the experimental site
were selected according to the following criteria:
1.
The available natural slope 1 - 2 percent.
2.
Areas with uniform soil texture and slope gradient.
An area of 2000 m2 (20 m width, 100 m length) was selected and
adjusted according to the uniformity and direction of slope, by
reorientation, so that no leveling was needed.
There are several methods of surveying contours, the water tube
method was chosen to use on the terrain in the area (Fig. 3.2).
70
Determination of contour lines was made with the water tube
level technique (Wright, 1984).
Components of the level:
-
One length of clear plastic tubing, 6-10 mm inside diameter
10-20 m long.
-
Two poles about 1.5 m long.
-
Four rubber straps made from inner tube to attach tubing to
poles.
-
Two rubber straps to mark the water levels in the tube.
-
One to two litres water.
71
72
Method of use:1.
Uncoil the tubing and lay it on the ground, stretching out any
bends.
2.
From a container of water held at shoulder height, siphon water
into one end of the tube, sucking from the other end, or fill the tube
by pouring into a funnel at one end.
3.
Remove any air bubbles.
4.
Tie each end of the tube to one of the poles. Then place both
poles together on a flat, smooth surface and hold them vertical
side-by-side. Add or remove water as a necessary to ensure that the
water levels are about 0.4-0.5 m below the tube ends.
5.
Attach a rubber strap to each tube so that it marks the position
of the water level.
6.
Place one of the poles so that it marks the end of the contour
whose alignment is to be determined. Take the second pole along
the suspected line of the contour, moving it up and down the slope
until the water level matches with the position of the rubber
marker. The second pole is now standing on the same contour as
the first, and a peg should be driven into the ground to mark the
spot.
7.
The second pole now remains stationary while the first one is
carried forward to look for a third point on the contour line.
8.
Proceed in the same manner until a suitable length of contour
has been marked out.
73
Hints:1.
Work during the coolest time of the day because heat causes
the tube to stretch, requiring frequent realignment of the rubber
straps which mark the water level. To re-adjust, repeat steps 4 and
5 above.
2.
Raising one end of the tube much higher than the other can spill
water. If this occurs repeat step 4 and 5.
3.
When starting on a new site, begin by tracing the highest
contour line required. If there are water - courses visible, start each
line on the main water-course and work away from it, first on one
side and then the other.
3.3 Water conservation treatments (techniques)
The adopted techniques were carried out before the onset of the
rainy season at the three sites, each site represented by a block. The
block as a combination of species, and the treatments was divided into
four equal plots of dimension 20 m x 25 m (Fig. 3.3). One of the four
plots remained as a control i.e no water harvesting technique was
used. The technique selection was based on the local farmers technical
know how and the availability of local construction materials. The
other plots were as follows:
a)
Crescent-shaped or curved terraces also called simi-circular
earth
74
bunds (T1):
75
A hybrid design amalgamating elements of the micro catchment
concept with aspect of the contour ridges techniques. The system
involves constructing ridges in short arcs (crescent-shaped).
The arcs lie on the contour at their ends, but dip below it at their
mid point. These arcs or “hoops” can be regarded as small micro
catchments, open of their up slope side and receiving runoff from out
side their immediate area.
Procedure
Earthen bunds were raised with “hoes” 30 cm around the
saucer-shaped pit (where the seedlings were planted). The distance
between crescent horn and the centre (seedling) equaled one-third (1⁄3)
the distance between the two centres (the distance between every two
centres within rows was 3 metres and between rows 2 m). The terraces
were placed on the contour line alternatively across the slope in order
to receive the sheet flow between upper terraces, Fig. 3.3 (a).
b) Triangular or v-shaped configuration (T2):
The triangle was 5 x 5 x 7 m. The two equal sides represent the
wings or dikes and the water come through the third side.
In all micro catchments as the name implies, there are small
often roughly square patches of bare ground which shed runoff into
basin excavated in the lowest corner, low earth bunds 20 - 30 cm high
from boundaries to micro catchment area and direct runoff into this
basin where typically single trees are planted. The dimension vary
with rainfall, soil and types of trees (or other plants) being grown.
76
Measuring 2 x 2 x 4 m with planting basin 25 cm deep and 2 m
square using hand tools.
Procedure: A pit 1.4 x 1.4 m and 0.25 m deep was dug at the right
angle of the triangle. A 30 - 40 cm high earthen dike was raised along
the two equal sides or wings of the triangle, the height of the dike was
graded from 30 cm at the point of intersection of the two equal sides
to 15 cm at the end of the wings. The water catchment techniques
were designed alternatively and perpendicular to slope direction and
distance between each two centres was 4 m within the rows and 2 m
between rows.
When the upper line was filled, excess water flows at the dike
edges forward lower one. The seedlings were planted in the angles of
the triangle that represent the water catchment. Crop was planted
along the inner side of the dike. There was a good chance for weeds
and herbs to grow on the area inside and behind the hole, Fig. 3.3 (b).
c) Ditches (trenches) with width and depth of 30 cm (T3):
This technique is found in most parts of central Sudan
particularly in areas with clay soils. The distance between each two
trenches were 2 metres. Trenches were laid perpendicular to the slope
direction. Soil was raised 30 cm towards the lower side. The distances
between plants were 2 m within the rows, Fig. 3.3 (c).
c)
Control or traditional, practice (To):
This plot was left flat ground to represent field practices
adopted by traditional farmers. Shallow pits were made at spacing of
2 x 2 m i.e. without employing any conservation measures.
77
78
79
80
3.4 Seedlings
The species selected for the experiment were Acacia tortilis
(Seyal) and Acacia nilotica (Sunt) which has a water proof testa. For
the seed to germinate prolonged submersion in water was done. Else,
it was treated with concentrated sulphuric acid which partially
consume the leathery testa and rendered it absorptive to water and
capable of germination. The seeds were also free from Die-back
disease. It was thought unwise to establish plantation from seeds
because of the losses that might be caused by dry spells. Seedlings
raised in nursery have better chances in a plantation (Badi, 1999).
Therefore the seedlings were raised in Kosti nursery in May to be
about two feet high when transplanted at the onset of the rainy season
in July to give the seedlings the full benefit of the rainy season. The
species were transplanted on the same day.
In all treatments including control plots the two species Acacia
nilotica and Acacia tortilis were sown in alternative rows i.e in one
row Acacia nilotica and the next Acacia tortilis and so on.
3.5 Fencing
A plantation was started very cautiously in well-fenced areas on
an experimental scale to avoid grazing by goat herds living almost
completely on the forest and do a great harm to young trees, so thorn
fences were erected.
3.6 Meteorological data
Rainfall: During all the season rain gauges were installed at
each site in order to measure rainfall amount in millimeters and
duration in hours. The other meteorological data was obtained from
the nearest meteorological stations (from Kosti and El Dueim).
3.7 Planting
After the first showers, seedlings were transplanted on each plot
at each site. In the pit plots the seedlings were placed at the middle
and the root zone was covered with fine soil. In trench plots the
seedlings were planted half way up on the side of the trench to avoid
81
possible water logging to the roots at spacing two meters. In the
crescent shaped and v-shaped plots the seedlings were planted half
way of inner side of the terrace. In the control plots the seedlings were
planted in shallow pits to cover the root zone at spacing of 2 x 2 m.
3.8 Soil characteristic (soil mechanical and physical properties)
Soil mechanical and physical analyses were performed at the
Soil Science Laboratory of the Faculty of Agriculture, University of
Khartoum.
a) Soil class:
Soil class was determined using the hydrometer method
proposed by (Bouyoucus, 1951). Samples were taken from four
random pits (60 cm deep) which were dug on each plot on the three
locations. From each plot 2 samples were taken at a depth of 30 cm
and 60 cm below the soil surface. A mean for each depth was taken to
represent soil class. Samples were taken before the rainy season.
b) Bulk density (g/cm3)
Three randomly selected locations each of an area of one metre
square were dug to a depth of one metre. Five clods, each of
approximately 5 cm in diameter were taken at an increment of 20 cm
from the surface to 60 cm depth. The mean bulk density of each depth
was calculated to give the value in g/cm3.
Many techniques have been proposed for estimation of soil bulk
density (Blake, 1965; Baver et al., 1972; Landon, 1984) which were
divided into two main groups:
82
1.
Methods requiring removal of a known volume of undisturbed
soil:
i- Core methods
ii- Coat sample methods
iii- Excavation
methods
2.
Radiation methods, which depend on condition of high energy
x-rays and gamma rays by soil in-situ:
i- x-rays diffraction and absorption
ii- Gamma rays scattering and absorption.
So the clod method was adopted in which the clod mass in air
(w1) was measured, then the clod was coated with paraffin wax, the
coated clod mass in air (w2) was measured, so the coated clod was
submerged in water then the volume of the coated clod (v2) was
obtained.
The wax mass (w3) = (w2) - (w1)
The wax volume (v3) = (w3) 0.9
Then the volume of the clod (v1) = (v2) - (v3)
So the bulk density = (w1) / (v1)
Where: 0.9 = The wax density in g/cm3
w1 = clod mass (gs)
v1 = clod volume (cm3)
3.9 Infiltration rate (cm/h)
Steady state infiltration rate was measured before rainy season
for each treatment (plot) using double ring infiltrometer following the
procedure described by Michael (1978). The double ring infiltrometer
83
was made of 0.2 cm thick metal sheet and consisted of two concentric
cylinders, 40 cm height with diameter of 30 cm for the inner ring and
40 cm for the outer one (Fig. 3.4). The infiltrometer was pressed
firmly in the soil and hammered gently with the help of wooden plate
until it was driven to a depth of 10 cm in the soil. A filter paper was
placed at the bottom of the inner cylinder to prevent disturbing the
surface of the soil, then water was poured gently into the inner
cylinder. The space between the inner and the outer cylinders was
filled immediately with water after filling the inner one to prevent the
horizontal water movement. Reading of the depth of the ponded water
in the inner cylinder was taken every 5 minutes then the rate of water
intake over the time is measured as described by Michael (1978).
The infiltration rate equations, for the different sites, were determined
before rainy season.
84
85
In order to evaluate the infiltration characteristic of the soil, a
functional relationship between accumulated infiltration (I) and
elapsed time (t), which is represented by the following equation, was
used:
I = ktn
(3.1)
In which:
I = accumulated infiltration (cm) in time t (min).
t = elapsed time (min).
n and k are characteristic constants
The data of I virsus t were plotted on a log-log paper and the
best fitting straight line was drawn through the plotted points. The
values of n (slope of the straight line) and k (the distance of the point
where the straight line cuts y-axis which indicates the initial rate of
infiltration) were determined from the linear relationship between I
and t.
Since the infiltration rate decreases with time and approaches
zero in case of heavy soils, the constant c, which is the basic
infiltration rate, was added so that the infiltration rate at long time will
not turn to zero.
The instantaneous infiltration rate (i) at any time (t) is obtained
by differentiating the above equation (3.1).
dI = nktn-1 + C = i
(3.2)
dt
Substituting the values of n, k and c in equation (3.2) ∴i = dI/dt
The basic infiltration rate (I) was also calculated for each treatment as
a mean of the last three instantaneous infiltration rate values.
86
3.10 Soil moisture content (%)
The soil moisture content was taken monthly starting at 15th
October. This parameter was determined gravimetrically. Soil samples
were augered from different locations on the three sites at 0.2 m
increment from the surface to a depth of 0.6 m. The samples were
oven dried at 105oC for 24 hours and weighed to determine moisture
content on dry weight basis (Michael, 1978).
Moisture content % = wt of wet sample-wt of oven dry sample x 100
wt of oven dry sample
Where: wt = the sample weight in gs
3.11 Plant parameters measurements
The effect of the conservation techniques on plant performance
was evaluated by measuring the following variables which were taken
monthly starting at 15th October.
1.
Plant survival: All survived plants were counted and divided by
the total numbers of the plant per plot to get % of survival.
2.
Plant height (cm): Twenty plants from each treatment were
randomly
selected,
tagged
and
labeled
for
plant
height
measurements. Plants were measured from soil surface to the top
of the plant using measuring tape (cm).
3.
The diameter at collar: A varnier caliper was used to get the
diameter in mm at the upper end of the stem.
4.
Number of branches per each plant were counted.
87
5.
Moisture content of the plant: In which 5 plants were randomly
selected and weighed in fresh and dry state (80oC for 48 hrs), the
average was obtained.
The dry matter = fresh wt-dry wt
dry wt
All measurements were analyzed and presented in tables or
graphs.
Data of each trail were analyzed as randomized block design
(R.B.D.) by standard analysis of variance techniques. Means of
significant (P < 0.05) were separated using Duncan’s Multiple Range
Test Procedure (Steel and Torrie, 1980).
88
CHAPTER FOUR
RESULTS AND DISCUSSION
4.1 Soil analysis
Table 1 Appendix D shows the particle distribution for the
different sites, depths and treatments. The amount of sand particles
was greater in the upper 30 cm than in the depth 30-60 cm for all
treatments in which the soil texture was sandy clay for the upper part
at all sites while the underlying layer was clay at all sites. This might
be due to eroded slope of the upper terraces where the sand and some
gravel was exposed as a result of erosion. This result is in agreement
with the findings of Goda (1987) who worked in the same area.
4.2 Soil physical properties
Soil bulk density, infiltration rates and soil moisture content
were measured prior to treatment application but soil moisture content
was measured monthly after the on set of the rainy season.
4.2.1 Soil bulk density
Table 2 Appendix D shows the results of the bulk density
values in g/cm3 for each 20 cm increment from the soil surface to
depth of 60 cm. The bulk density was found to increase with depth,
with an average of 1.36 g/cm3 at Humra, 1.44 g/cm3 at Aba and 1.67
g/cm3 at Kileikis where the average bulk density was found to be the
greatest. This result may be attributed to the soil texture of the three
sites (Table 1 Appendix D). Therefore as the clay percentage increases
the bulk density also increases (Fig. 4.1). This result is in agreement
with the findings of Salah (1991).
89
Fig. 4.1.
90
4.2.2 Infiltration rate
Table 3 Appendix D shows the observed instantaneous
infiltration rate (cm/h), the average values of basic infiltration rate
(cm/h) and the average values of the accumulated infiltration depth
(cm) versus opportunity time.
For all water harvesting measures, the initial infiltration rate
values were higher at the beginning of the measurement. The values
then decreased gradually and continued for more than half an hour
before reaching a relatively steady-state condition. At Humra area the
instantaneous infiltration rate of the first five minutes elapsed time
was 30.4, 29.2, 26.8 and 24.8 cm/h for crescents, intersections, ditches
and control treatments, respectively. The basic infiltration rate of 6.4
cm/h at 50 minutes elapsed time for crescents while 4.4, 3.3 and 3.2
cm/h at 40 minutes elapsed time for intersections, ditches and control,
respectively. The accumulated infiltration depth of 60 minutes elapsed
time was 13.0, 10.8, 10.5 and 8.5 cm for crescents, intersections,
ditches and control, respectively. At Aba the instantaneous infiltration
rate of the first five minutes elapsed time was 28.4, 26.4, 24.8
and 16.8 cm/h for crescents, intersections, ditches and control,
respectively. The basic infiltration rate values were found to be 6.4
and 4.4 cm/h at 45 minutes elapsed time for crescents and
intersections, and 3.2 and 2.8 cm/h at 40 minutes elapsed time for
ditches and control. The accumulated infiltration depths after one hour
from the beginning were 11.7, 10.2, 9.8 and 7.9 cm for crescents,
intersections, ditches and control respectively. At Kileikis the initial
infiltration rate of the first five minutes elapsed time was 20.0, 15.2,
91
14.5 and 11.2 cm/h after crescents, intersections, ditches and control,
respectively. The final infiltration rate was 6.0, 4.4, 3.0 and 2.5 cm/h
for 45 minutes elapsed time for crescents, intersections, ditches and
control, respectively. The accumulated infiltration depth after 60
minutes elapsed time was 11.1, 8.9, 7.9 and 7.6 cm for crescents,
intersections, ditches and control treatments, respectively. Fig 4.2
shows the curves of accumulative infiltration depth (cm) and
instantaneous infiltration rate cm/h for the aforementioned treatments.
From the obtained results at the three different sites the basic
infiltration rate can be described more or less as moderate. This
moderate infiltration rate is a characteristic of the soil class (Table 1
Appendix D) of the experimental area which is sandy clay.
4.2.3 Soil moisture content (SMC)
The soil moisture content was closely linked to the amount of
rainfall during the rainy season. Table 4 Appendix D shows the
monthly rainfall records for the experimental sites during the season
2003/04. The total seasonal rainfall was 240 mm at Humra, 314.2 mm
at Aba and 380.4 mm at Kileikis. The records of soil survey (1976) for
arid and semi-arid zone gave a range for the means of annual rainfall
from 250-400 mm at the northern part and 400-800 mm at the
southern part, Humra which lies within the northern part, Aba in the
middle and Kileikis within the southern part deviated slightly from the
mean range i.e their records were less than the mean range. The three
sites represented different sets of climatic conditions. The southern
site was wetter with a total rainfall of 380.4 mm.
Fig. 4.2.
92
The total rainfall of the southern site was 205.2 mm below longterm average (585.6 for the last 50 years). It was above long term
average only during October at Kileikis site. At Humra site rains
started late (July) and ceased earlier (September), while at the other
two sites (Kileikies and Aba) rains started in June and ceased in
October. At all sites August had a much higher rainfall approximately
50%, 60% and 75% of the total at Kileikis, Aba and Humra
respectively. Also, during August long continuous periods of rains and
cloudy weather prevailed.
Fig 4.3 and Table 5 Appendix D show the total monthly rainfall
received at the sites during the experimental period, as well as the
50-year monthly average (1953-2002).
The effect of the experimental treatments and sites on soil
moisture content measurements were carried out as described in
section 3-10. Fig 4.4 and Table 6 Appendix D show the means of soil
moisture content. Analysis of variance for soil moisture content for
different time intervals were shown in Table 12 Appendix D. The soil
moisture content was closely linked to the amount of rainfall during
the rainy season. Table 4 Appendix D shows that a considerable
variation in rainfall was encountered during season 2003/04,
consequently a considerable variation in soil moisture content
resulted.
The analysis of variance for the soil moisture content Table
12 Appendix D at the four different treatments after the 1st, 2nd, 3rd, 4th,
5th, 6th and 7th readings showed a highly significant difference
93
Fig. 4.3.
94
Fig. 4.4.
95
(P ≤ 0.01) existed among the treatments, while 8th, 9th and 10th
readings showed no significant difference between them (P ≥ 0.05).
After the first seven readings crescents and intersections were not
significantly different from each other but were significantly different
from the ditches and the control which were not significantly different
from each other. This result showed that crescents and intersections
were the best treatments to conserve moisture compared to ditches and
control. The result of all readings showed that the crescents were the
best followed by intersections, ditches and control respectively. After
the 8th and 9th readings the moisture level decreased due to the effect
of summer period and increased after the 10th reading due to the onset
of rains.
These results agreed with the findings obtained by Badi (1963).
The reasons for the low moisture content obtained by the control
treatments may be attributed to the high surface soil bulk density, low
porosity, retarded infiltration and low water holding capacity of the
soil compared to the other treatments.
The analysis of variance for soil moisture content (Table 12
Appendix D) at the three sites after the 1st, 2nd and 3rd readings showed
a significant difference (P ≤ 0.05), after 4th, 5th, 6th and 7th readings
showed a highly significant difference (P ≤ 0.01) and after 8th, 9th and
10th readings showed no significant difference (P ≥ 0.05) among the
blocks. The results of all readings at Kileikis was the best followed by
Aba and Humra. The first seven readings at Humra showed a
significant difference from Kileikis and Aba, which showed no
significant difference between them. The 8th and 9th readings showed
that the level of the soil moisture content decreased due to the effect
of summer period and the level of the moisture content at the 10th
reading increased due to the onset of rain.
96
4.3 The effect of the experimental treatments and sites on the
plant survival
All plant measurements were carried out as described in section
3-11. They were all affected by the soil moisture content throughout
the reading intervals. The data of plant survival were shown in
Fig. 4.5 (a and b) and Table 7 Appendix D. Analysis of variance for
plant survival for different time intervals were shown in (Table 12
Appendix D).
The analysis of variance for the plant survival (Table 12
Appendix D) for the 1st, 2nd, 3rd, 4th and 5th readings showed a highly
significant difference (P ≤ 0.01). The 6th and 7th readings although
showed a significant difference (P ≤ 0.05) and the final three readings
were not significantly different (P ≥ 0.05) for the Acacia nilotica and
Acacia tortilis. In all treatments, the crescents were the best followed
by intersections, ditches and control treatments. The 1st, 2nd, 3rd, 4th
and 5th readings showed no significant difference between crescents
and intersections. Also ditches and control showed no significant
difference but crescents and intersections were significantly different
from the ditches and control treatments. The last three readings were
not different. The 6th and 7th readings showed a significant difference
between crescents and control treatments, while intersections and
ditches showed no significant difference but both of them were not
significantly different from crescents and control treatments. All the
plants died at the ditches and control treatments after the 7th reading,
while the plants grown in the crescents and intersection continued to
survive. This result agreed with the finding of Choparts (1979) and
Perrier (1986).
97
Fig. 4.5a
98
Fig. 4.5b
99
The analysis of variance for plant survival (Table 12 of
Appendix D) at the three experimental sites after the 1st, 2nd, 3rd, and
5th readings showed no significant difference (P ≥ 0.05). The 6th and
7th readings showed a significant difference (P ≤ 0.05). The final three
readings were not significantly different (P ≤ 0.05). Kileikis and Aba
throughout showed that the readings of Acacia nilotica were greater
than Acacia tortilis (Table 7 Appendix D). At all readings Kileikis
was the best followed by Aba and Humra. The 6th and 7th readings for
Kileikis and Aba were not significantly different from each other
while Humra was significantly different from both Kileikis and Aba.
The number of plants survived at the three site declined gradually
according to the low level of moisture due the effect of the summer
which increased the rate of evaporation.
4.4 The effect of experimental treatments and sites on the shoot
length (SL)
The data of shoot length were shown in Fig. 4.6 (a and b) and
Table 8 Appendix D. Analysis of variance for shoot length for
different time intervals were shown in Table 12 Appendix D.
The analysis of variance for the shoot length (Table 12
Appendix D) for the 2nd reading showed a highly significant
difference (P ≤ 0.01), but the 1st, 3rd, 4th, 5th, 6th, 7th, 8th, 9th and 10th
readings were not significantly different (P ≥ 0.05) from each other.
The 1st, 3rd and 7th readings showed a significant difference between
crescents and control treatments, while intersections and ditches were
100
Fig.4.6a
101
Fig.4.6.b
102
not significantly different from each other but both of them were not
significantly different from crescents. The 2nd reading of crescents and
control treatments were highly significantly different from each other,
while ditches were not significantly different from control treatments
and intersections which were not significantly different from
crescents. At the 8th, 9th and 10th readings the plants in ditches and
control treatments completely died while the plants grown in the
crescents and intersections continued to survive to the last reading.
This result coincided with the results obtained by Badi (1963).
The analysis of variance for shoot length (Table 12 Appendix
D) at the three experimental sites after the 1st, 2nd, 3rd, 4th, 5th, 7th, 8th,
9th and 10th readings were not significantly different (P ≥ 0.05). The 6th
reading showed a highly significant difference (P ≤ 0.01). At all
reading Acacia nilotica and Acacia tortilis grown at Kileikis gave the
best results followed by Aba and Humra respectively. Acacia tortilis
in Humra was better than Acacia nilotica in all readings. The 4th, 5th
and 7th readings showed a significant difference between Kileikis and
Humra while Aba was not significantly different from both Kileikis
and Humra. The 6th reading showed no significant difference between
Kileikis and Aba but Humra showed a highly significant difference
from both Kileikis and Aba.
103
4.5 The effect of the experimental treatments and sites on
diameter at collar (DCR)
The data of diameter at collar is shown in Fig. 4.7 (a and b) and
Table 9 Appendix D. Analysis of variance for diameter at collar for
different time intervals were shown in Table 12 Appendix D.
At all readings the best mean was given by crescents followed
by intersection, ditches and control treatments, respectively. The 1st
and 2nd readings showed that crescents, intersections and control
treatments were significantly different from each other while ditches
showed no significant different from intersection and control
treatments but still significantly different from crescents. In the
control treatments and ditches, the plants completely died at the 8th
reading i.e. the parameter ceased due to the death of the plant, on the
other hand crescents were the best. This result coincided with the FAO
(1976) results of the experiment of Arabic gum belt in Kordofan.
The analysis of variance for diameter at collar (Table 12
Appendix D) at the three sites after the first three and last four
readings showed no significant difference (P ≤ 0.05). The 4th and 5th
readings were significantly different (P ≤ 0.05) while the 6th reading
showed a highly significant difference (P ≤ 0.01). At all readings
Kileikis was the best followed by Aba and Humra respectively.
The 4th, 5th and 6th readings for Kileikis and Aba were not significantly
different from each other, while Humra showed a significant
difference from both Kileikis and Aba. The 7th reading showed a
104
fig. 4.7a
105
Fig. 4.7b
106
significant difference between Kileikis and Humra but Aba was not
significantly different from Kileikis and Aba. At all readings for
Acacia nilotica and Acacia tortilis Kileikis was the best followed by
Aba and Humra respectively. Acacia tortilis in Humra was better than
Acacia nilotica in all readings.
4.6 The effect of Experimental treatments and sites on the number
of branches per plant (NOB)
The data were presented in Fig. 4.8 (a and b) and Table 10
Appendix D. Analysis of variance for (NOB) for different time
intervals were shown in Table 12 Appendix D. The analysis of
variance for the (NOB) (Table 12 Appendix D) the 1st and 2nd readings
were highly significantly different (P ≤ 0.01).
The 4th, 6th, 7th, 8th, 9th and 10th readings were not significantly
different. At all readings the crescents were the best followed by
intersections, ditches and control, respectively. Both the 1st and 2nd
readings showed a significant difference between crescents,
intersections and control treatments, while ditches were not
significantly different from intersections and control treatments but
still significantly different from crescents. In the 3rd and 5th readings,
although the crescents were significantly different from control
treatments but both of them were not significantly different from
intersections and ditches which were not significantly different from
each others. All the plants of ditches and control treatments died at the
8th readings.
107
Fig. 4.8a
108
Fig. 4.8b
109
The analysis of variance for (NOB) at the three sites, all
readings except the 6th and 7th readings were not significantly
different (P ≥ 0.05), the 6th reading showed a highly significant
difference (P ≤ 0.01). At all readings Kileikis was the best followed by
Aba and Humra respectively. At the 6th reading Kileikis and Aba were
not significantly different from each other but significantly different
from Humra. The 7th reading showed a significant difference between
Kileikis and Humra but Aba was not significantly different from both
of them. All readings of Acacia nilotica and Acacia tortilis, Kileikis
was the best followed by Aba and Humra, respectively. Acacia tortilis
in Humra was better than Acacia nilotica in all readings.
4.7 The effect of experimental treatments and sites on the plant
moisture content (PMC)
The data of the plant moisture content is shown in Fig. 4.9
(a and b) and Table 11 Appendix D. Analysis of variance for (PMC)
for different time interval were shown in Table 12 Appendix D.The
analysis of variance for (PMC) (Table 12 Appendix D) in the four
different treatments the 1st and 2nd readings showed a highly
significant difference (P ≤ 0.01). All the other readings were not
significantly different (P ≥ 0.05) from each other. Through all
readings crescents were the best followed by intersections, ditches and
control respectively. At the 1st reading, the crescents, intersections and
control treatments were significantly different from each other, while
110
Fig. 4.9a
111
Fig. 4.9b
112
ditches showed no significant difference from intersections and
control treatments but still significantly different from crescents. The
2nd reading showed no significant difference between intersections,
ditches and control treatments but crescents showed a significant
difference from intersections, ditches and control treatments. The 5th
reading showed no significant difference between ditches and control
treatments but both of them were significantly different from
crescents which was not significantly different from intersections
which were not significantly different from both ditches and control
treatments. At the 8th reading all the plants in ditches and control
treatments died.
The analysis of variance for (PMC) (Table 12 Appendix D) at
the three sites after the first three and last four readings were not
significantly different (P ≥ 0.05) from each other. The 4th reading
showed a significant difference (P ≤ 0.05), the 5th and 6th readings
showed a highly significant difference and the 7th reading there was a
significant difference between Kileikis and Humra, however, Aba was
not significantly different from both of them. At the 4th, 5th and 6th
readings Kileikis and Aba showed no significant difference while
Humra was significantly different from both of them. At all readings
in Acacia nilotica and Acacia tortilis Kileikis was the best followed
by Aba and Humra respectively. Acacia tortilis in Humra was better
than Acacia nilotica in all readings.
113
CHAPTER FIVE
CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions
The following conclusions can be drawn from the results of this
study:
1.
Water harvesting techniques significantly affected soil physical
properties (bulk density, porosity, infiltration rate and moisture
content).
2.
Superiority in soil moisture content was achieved by crescents,
intersections, ditches and control treatments respectively.
3.
Crescents and intersections (network or diamonds) were found
to be economically and technically feasible specially in small
holdings than ditches and the control treatments because they
retain more moisture content.
4.
The effect of water harvesting techniques on water conservation
was consistent with plant parameters.
5.
The study indicated that plant parameters differences between
ditches and control were small when rainfall was below normal.
6.
Differences according to the plantation in the different three
sites Humra, Aba and Kileikis were due to variation in moisture
status, which was closely linked to the amount of rainfall water
accordingly Kileikis was superior to Aba and Humra respectively.
114
7.
The plant parameters of Acacia nilotica were better than Acacia
tortilis at Kileikis, while Acacia tortilis was better than Acacia
nilotica at Humra area.
5.2 Recommendations
According to the results obtained and conclusions drawn from
this study, the following recommendations can be made:
1.
For tree species, Acacia tortilis, subsp. Spirocarpa ‘Sammur’
(Arabic) is recommended for the study area.
2.
Further research should be conducted to investigate the
performance of different tree species under water harvesting
techniques used in this study.
3.
Further investigations are recommended to study other water
harvesting methods.
115
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of a Symposium - Morogoro, Tanzania - 1976, University of Dar es Salam, International
Development Research Centre, IDRC, P. 30.
Ahmed, A.E. (1976). On thinning Acacia nilotica stands along the
Blue Nile, Sudan Silve III (21).
Anderson, D.M.W. and Brenan, J.P.M. (1975). Chematoxanomic
aspects of the gum exudates from some sub-species of
Acacia tortilis (Forsk) Hayne. Biossieva 24: 307-309.
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APPENDICES
130
Appendix A
Table 1. Ten years mean monthly and the total annual rainfall values (mm) at Kosti Station (1953-2002).
Duration
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Total
1953-62
0.0
0.0
0.0
2.6
40.7
85.0
208.8
252.2
128.5
15.0
0.0
0.0
733
1963-72
0.0
0.0
0.0
3.1
17.3
89.0
203.0
220.0
119.2
27.1
0.0
0.0
680
1973-82
0.0
0.0
0.0
8.3
27.6
63.7
166.8
177.8
107.5
13.9
0.0
0.0
565
1983-92
0.0
0.0
0.0
6.8
38.6
57.0
136.3
164.2
45.2
11.9
0.0
0.0
460
1993-02
0.0
0.0
0.0
0.0
37.5
63.9
136.6
158.2
68.0
25.8
0.0
0.0
490
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
Appendix D
Table 1. Soil mechanical analysis for the three locations, different
depths and treatments.
Treatments
Intersection
Crescents
Ditches
Control
Intersection
Crescents
Ditches
Control
Intersection
Crescents
Ditches
Control
Depths
(cm)
0 – 30
30 - 60
0 – 30
30 - 60
0 – 30
30 - 60
0 – 30
30 - 60
0 – 30
30 - 60
0 – 30
30 - 60
0 – 30
30 - 60
0 – 30
30 - 60
0 – 30
30 - 60
0 – 30
30 - 60
0 – 30
30 - 60
0 – 30
30 - 60
Sand%
Silt%
(1) Humra
7
5
7
5
7
5
7
5
(2) Aba
40
7
38
5
44
7
40
5
47
7
38
5
45
7
39
5
(3) Kileikis
35
18
33
17
36
20
35
19
38
21
32
16
38
20
32
17
48
46
48
45
47
45
46
44
146
Clay%
Soil
texture
45
49
43
50
42
48
44
46
Sandy clay
Clay
Sandy clay
Clay
Sandy clay
Clay
Sandy clay
Clay
49
47
44
50
45
49
41
49
Sandy clay
Clay
Sandy clay
Clay
Sandy clay
Clay
Sandy clay
Clay
47
50
44
46
41
52
42
51
Sandy clay
Clay
Sandy clay
Clay
Sandy clay
Clay
Sandy clay
Clay
Table 2. The values of bulk density in g/cm3 for the three sites.
Bulk density g/cm3
Depth (cm)
(1) Humra
(2) Aba
(3) Kileikis
0 – 20
1.33
1.41
1.62
20 – 40
1.37
1.44
1.66
40 – 60
1.39
1.47
1.73
Average
1.36
1.44
1.67
147
Table 3. The instantaneous infiltration rate (cm/hr), the average values of basic infiltration rate
(cm/hr) and the average values of the accumulated infiltration depth (cm).
Crescents
Intersections
Average acc.
Infilt. rate
Ditches
Average acc.
Infilt. rate
infilt. depth
(cm/hr)
Average
Infilt. rate
infilt. depth
(cm/hr)
(cm)
Control
Average
Infilt. rate
acc. infilt.
(cm/hr)
(cm)
acc. infilt.
(cm/hr)
depth (cm)
depth (cm)
(1) Humra
5
30.4
1.5
29.2
2.4
26.4
2.2
24.8
1.1
10
27.2
2.5
25
4.5
22
4.5
18
1.7
15
23.2
4.2
20
6.3
17
6.1
12
2.5
20
20
5.8
13.2
7.4
12
7.4
9.2
3.7
25
17
7.4
8.4
8.1
9.2
8.4
6.8
4.3
30
14
8.6
6
8.6
6.8
9.1
4.5
5
35
11.2
9.6
5
9
4
9.6
3.3
5.4
40
8.8
10.3
4.4
9.3
3.3
10
3.2
6
45
7.6
10.9
4.4
9.6
3.3
10.1
3.2
6.9
50
6.4
11.9
4.4
10
3.3
10.2
3.2
7.6
55
6.4
12.5
4.4
10.4
3.3
10.3
3.2
8.1
60
6.4
13
4.4
10.8
3.3
10.5
3.2
8.5
(2) Aba
5
28.4
1.8
26.4
2.2
24.8
2.7
16.8
1.4
10
24
3.5
22
4.1
19.6
3.4
14
2.5
15
20
5
17.5
5.6
14
4.2
12
3.5
20
16.4
6.3
14
6.7
9.2
5.5
10.4
4.3
25
13.5
7.4
11.2
7.4
6.4
6.5
8.5
5
30
10.8
8.3
8.8
8.1
4.4
7.4
6.5
5.2
35
9
9
6.8
8.6
3.7
8
4.4
5.8
40
7.5
9.7
5.2
9
3.2
8.5
2.8
6.2
148
45
6.4
10.2
4.4
9.3
3.2
8.9
2.8
6.8
50
6.4
10.7
4.4
9.6
3.2
9.3
2.8
7
55
6.4
11.2
4.4
9.9
3.2
9.5
2.8
7.3
60
6.4
11.7
4.4
10.2
3.2
9.8
2.8
7.9
(3) Kileikis
5
20
1.7
15.2
1.3
14.5
1
11.2
0.9
10
18.4
3.2
13.2
2.4
13
1.5
8.5
1.6
15
16.4
4.6
11.2
3.3
11.5
2
7
2.1
20
14
5.8
9.6
4.1
9
2.8
6.2
3.1
25
12.4
6.8
8
4.7
7.1
3.8
5
4.2
30
10.5
7.7
6.8
5.7
5.5
4.5
4.4
5
35
9.2
8.5
5.8
5.8
4.5
6.1
3.5
5.8
40
7.2
9.1
5
6.2
3.75
6.5
3
6.4
45
6
9.6
4.4
7.3
3
6.9
2.5
7
50
6
10.1
4.4
7.9
3
7.3
2.5
7.6
55
6
10.6
4.4
8.5
3
7.7
2.5
7.6
60
6
11.1
4.4
8.9
3
7.9
2.5
7.6
149
Table 4. Monthly rainfall records in mm/month at Kileikis, Aba
and Humra.
Months
Sites
Total
June
July
August
Kileikis
11.1
48.5
191.1
93.2
36.5
380.4
Aba
4.3
35.0
188.3
74.2
12.4
314.2
-
26.0
180.0
34.0
-
240.0
Humra
150
September October
Table 5. Monthly rainfall (mm) for the experimental sites and the
long-term average monthly rainfall (1953-2002).
Months
Location
Total
April
May
June
July
Aug.
Sept.
Oct.
Kileikis
-
-
11.1
48.5
191.1
93.2
36.5
380.4
Aba
-
-
4.3
35.0
188.3
74.2
12.4
314.2
Humra
-
-
-
26.0
180.0
34.0
-
240.0
4.7
34.4
71.3
170.3
195.6
93.7
18.7
585.6
Monthly
average
rainfall*
* Source: Kosti Meteorological Station.
151
Table 6. Duncan’s multiple range test for variable soil moisture
content in 10 readings.
Measurement
Experimental
sites
Means
Duncan
grouping
Kileikis
Aba
Humra
16.98
16.58
15.48
A
A
B
Kileikis
16.50
16.08
A
A
Aba
Humra
15.28
B
Kileikis
Aba
Humra
16.28
15.98
14.91
A
A
B
Kileikis
Aba
Humra
16.19
15.72
14.37
A
A
B
Kileikis
15.73
15.23
A
A
Aba
Humra
14.11
B
Kileikis
Aba
Humra
15.42
15.02
14.00
A
A
B
Kileikis
14.70
14.30
A
A
13.10
B
Experimental
treatment
T1
T2
T3
T4
T1
T2
Means
Duncan
grouping
17.50
17.30
16.10
15.40
17.00
16.60
A
A
B
B
A
A
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
15.63
14.90
16.80
16.60
15.40
14.70
16.40
16.20
14.92
14.60
16.20
16.00
B
B
A
A
B
B
A
A
B
B
A
A
T3
T4
T1
T2
T3
T4
T1
T2
14.87
14.50
15.90
15.40
14.40
14.10
13.97
13.31
B
B
A
A
B
B
A
A
T3
T4
Kileikis
12.00
A
T1
Aba
11.92
A
T2
8
Humra
10.22
A
T3
T4
Kileikis
12.00
A
T1
Aba
11.90
A
T2
9
Humra
10.00
A
T3
T4
Kileikis
14.75
A
T1
Aba
14.20
A
T2
10
Humra
14.08
A
T3
T4
Means with the same letter are not significantly different.
12.30
12.00
12.17
12.00
10.07
10.07
12.06
12.00
10.12
10.00
14.50
14.57
14.17
14.10
B
B
A
A
A
A
A
A
A
A
A
A
A
A
1
2
3
4
5
6
7
Aba
Humra
C.V
2.01
2.32
2.47
3.38
1.20
2.81
8.24
152
15.82
17.40
2.61
Table 7. Duncan’s multiple range test for plant survival in 10 readings.
Measure
ment
Experim
ental site
Kileikis
1
Aba
Humra
Kileikis
2
Aba
Humra
Kileikis
3
Aba
Humra
Kileikis
4
Aba
Humra
Means
79.50
74.50
69.50
72.50
67.50
62.50
67.50
62.50
57.0
64.50
59.50
54.50
Acacia nilotica
Experim
Duncan
C.V
ental
grouping
treat.
A
A
A
A
A
A
A
A
A
A
A
A
13.08
14.44
15.59
16.38
Acacia tortilis
Means
T1
84.00
T2
T3
81.00
70.00
T4
63.00
T1
77.00
T2
T3
74.00
63.00
T4
56.00
T1
72.00
T2
T3
69.00
58.00
T4
56.00
T1
69.00
T2
T3
66.00
55.00
T4
48.00
Duncan
grouping
A
A
B
Experim
ental site
Means
Kileikis
76.50
Aba
Humra
71.50
70.50
Duncan
grouping
A
A
A
C.V
6.71
B
A
A
B
Kileikis
69.50
Aba
Humra
64.50
63.50
A
A
A
7.41
B
A
A
B
Kileikis
64.50
Aba
Humra
59.50
58.50
A
A
A
8.0
B
A
A
B
B
153
Kileikis
61.50
Aba
Humra
56.50
55.50
A
A
A
8.40
Experimental
treat.
Means
T1
82.33
T2
T3
79.33
68.33
A
A
B
T4
61.33
B
T1
76.33
T2
T3
72.33
61.33
A
BA
B
T4
54.33
C
T1
70.33
T2
T3
67.33
56.33
A
A
B
T4
54.33
B
T1
67.33
T2
T3
64.33
53.33
A
A
B
T4
46.33
B
Duncan
grouping
Table 7 cont.
5
6
7
8
9
10
Kileikis
Aba
Humra
61.50
56.50
51.50
A
A
A
Kileikis
Aba
Humra
48.51
43.21
25.32
A
A
B
Kileikis
Aba
Humra
46.54
40.22
22.77
A
A
B
Kileikis
Aba
Humra
37.0
29.25
21.75
A
A
A
Kileikis
Aba
Humra
35.64
27.22
18.00
A
A
A
Kileikis
Aba
Humra
25.63
17.31
10.0
A
A
A
17.25
22.29
23.26
24.56
14.26
14.26
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
66.00
63.00
52.00
45.00
58.33
49.67
39.02
37.21
56.41
45.57
32.06
0.0
46.32
35.21
0.0
0.0
36.25
31.82
0.0
0.0
26.13
24.86
0.0
0.0
A
A
B
B
A
BA
BA
B
A
BA
BA
B
A
A
A
A
A
A
A
A
A
A
A
A
154
Kileikis
Aba
Humra
58.50
53.50
52.50
A
A
A
Kileikis
Aba
Humra
41.67
37.34
27.05
A
A
B
Kileikis
Aba
Humra
39.22
33.91
26.26
A
A
B
Kileikis
Aba
Humra
33.59
27.18
22.62
A
A
A
Kileikis
Aba
Humra
32.92
25.87
20.39
A
A
A
Kileikis
Aba
Humra
30.97
15.25
12.00
A
A
A
8.85
21.19
22.24
23.72
9.56
9.56
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
64.33
61.33
50.33
43.33
55.67
47.23
37.19
27.78
52.72
45.21
35.00
27.49
42.37
39.44
0.0
0.0
31.73
29.0
0.0
0.0
21.66
19.23
0.0
0.0
A
A
B
B
A
BA
BA
B
A
BA
BA
B
A
A
A
A
A
A
A
A
A
A
A
A
Table 8. Duncan’s multiple range test for shoot length in 10 readings.
Acacia nilotica
Measur
Experi
ement
mental
Duncan
Means
site
1
2
3
4
groupin
Acacia tortilis
Experi
C.V
mental
Means
Duncan
Experi
groupin
mental
g
site
Duncan
Means
groupin
g
treat.
T1
39.26
A
Kileikis
T2
36.27
BA
T3
29.21
BA
T4
21.26
B
T1
39.92
A
Kileikis
34.33
A
T2
36.88
BA
Aba
31.13
A
T3
29.86
BC
Humra
31.10
A
T4
23.75
C
T1
40.0
A
Kileikis
34.88
A
T2
36.92
BA
Aba
31.34
A
T3
29.43
BA
Humra
22.34
A
T4
21.32
B
T1
40.91
A
Kileikis
34.45
A
T2
36.34
A
Aba
32.94
BA
T3
29.89
A
Humra
23.74
B
T4
23.11
A
Kileikis
35.85
A
Aba
32.29
A
Humra
24.85
A
Kileikis
36.00
A
Aba
32.63
A
Humra
30.52
A
Kileikis
36.00
A
Aba
32.67
A
Humra
22.21
A
Kileikis
36.00
A
Aba
33.29
BA
Humra
23.61
B
20.37
10.66
14.22
12.91
155
ExperiC.V
mental
Means
Duncan
grouping
g
treat.
33.33
A
T1
38.84
A
Aba
30.98
A
T2
34.22
BA
Humra
25.18
A
T3
27.14
BA
T4
20.37
B
T1
39.81
A
T2
34.79
BA
T3
27.82
BC
T4
22.29
C
T1
39.97
A
T2
35.47
BA
T3
27.0
BA
T4
20.90
B
T1
40.90
A
T2
36.33
A
T3
29.29
A
T4
22.34
A
25.81
14.73
17.81
16.32
Table 8 cont.
5
6
7
8
9
10
Kileikis
Aba
Humra
36.18
32.85
23.69
A
BA
B
Kileikis
Aba
Humra
36.30
32.96
23.94
A
A
B
Kileikis
Aba
Humra
35.70
32.97
23.98
A
BA
B
Kileikis
Aba
Humra
35.75
32.98
24.00
A
A
A
Kileikis
Aba
Humra
20.36
18.92
17.31
A
A
A
Kileikis
Aba
Humra
20.38
18.94
17.32
A
A
A
12.95
21.79
25.25
33.85
9.39
9.41
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
40.93
36.35
29.90
22.37
40.95
36.38
29.03
22.40
40.97
36.40
29.96
22.40
40.99
36.42
0.0
0.0
41.01
36.44
0.0
0.0
41.02
36.47
0.0
0.0
A
A
A
A
A
A
A
A
A
BA
BA
B
A
A
A
A
A
A
A
A
A
A
A
A
156
Kileikis
Aba
Humra
35.62
32.69
23.73
A
BA
B
Kileikis
Aba
Humra
35.68
32.73
23.95
A
A
B
Kileikis
Aba
Humra
35.69
32.82
23.96
A
BA
B
Kileikis
Aba
Humra
35.70
32.84
23.99
A
A
A
Kileikis
Aba
Humra
20.35
18.91
17.31
A
A
A
Kileikis
Aba
Humra
20.37
18.92
17.32
A
A
A
16.73
21.81
25.27
33.85
9.32
9.34
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
40.92
36.35
29.31
22.35
40.93
36.36
29.35
22.38
40.96
36.37
29.38
22.39
40.98
36.39
0.0
0.0
41.0
36.41
0.0
0.0
41.0
36.44
0.0
0.0
A
A
A
A
A
A
A
A
A
BA
BA
B
A
A
A
A
A
A
A
A
A
A
A
A
Table 9. Duncan’s multiple range test for diameter at color in 10 readings.
Acacia nilotica
Measur-
Experi
ement
mental
Duncan
Means
site
1
2
3
4
groupin
Acacia tortilis
Experi
C.V
mental
Means
Duncan
Experi
groupin
mental
g
site
Duncan
Means
groupin
g
treat.
T1
3.16
A
Kileikis
T2
3.14
B
T3
3.06
CB
T4
3.01
C
T1
3.18
A
Kileikis
3.14
A
T2
3.16
B
Aba
3.10
A
T3
3.08
CB
Humra
3.08
A
T4
3.02
C
T1
3.20
A
Kileikis
3.17
A
T2
3.16
A
Aba
3.12
A
T3
3.10
A
Humra
3.10
A
T4
3.04
A
T1
3.22
A
Kileikis
3.20
A
T2
3.20
A
Aba
3.15
A
T3
3.13
A
Humra
3.11
B
T4
3.06
A
Kileikis
3.13
A
Aba
3.10
A
Humra
3.06
A
Kileikis
3.15
A
Aba
3.11
A
Humra
3.07
A
Kileikis
3.18
A
Aba
3.12
A
Humra
3.09
A
Kileikis
3.21
A
Aba
3.16
A
Humra
3.10
B
5.24
4.86
8.55
9.40
157
ExperiC.V
mental
Means
Duncan
grouping
g
treat.
3.19
A
T1
3.16
A
Aba
3.09
A
T2
3.14
B
Humra
3.07
A
T3
3.06
CB
T4
3.00
C
T1
3.18
A
T2
3.16
B
T3
3.07
CB
T4
3.02
C
T1
3.20
A
T2
3.18
A
T3
3.09
A
T4
3.04
A
T1
3.22
A
T2
3.20
A
T3
3.12
A
T4
3.06
A
3.18
2.72
4.98
6.01
Table 9 cont.
5
6
7
8
9
10
Kileikis
Aba
Humra
3.24
3.18
3.11
A
Kileikis
Aba
Humra
3.19
3.20
2.36
A
Kileikis
Aba
Humra
3.30
2.45
2.37
A
Kileikis
Aba
Humra
2.44
2.46
1.60
A
Kileikis
Aba
Humra
1.71
1.66
1.60
A
Kileikis
Aba
Humra
1.73
1.68
1.61
A
A
B
A
B
BA
B
A
A
A
A
A
A
8.72
9.18
7.64
10.07
10.8
10.31
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
3.24
3.22
3.15
2.08
3.16
3.24
3.17
2.10
3.28
3.27
3.20
1.07
3.30
3.29
0.00
0.00
3.32
3.31
0.00
0.00
3.35
3.34
0.00
0.00
Kileikis
Aba
Humra
3.23
3.16
3.12
A
A
A
Kileikis
Aba
Humra
3.23
3.17
2.37
A
A
A
Kileikis
Aba
Humra
3.26
2.41
2.38
A
A
A
Kileikis
Aba
Humra
2.49
2.43
1.60
A
A
A
Kileikis
Aba
Humra
1.69
1.64
1.61
A
A
A
Kileikis
Aba
Humra
1.71
1.66
1.62
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
158
A
B
A
B
BA
B
A
A
A
A
A
A
7.56
8.26
6.58
9.27
9.45
9.86
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
3.23
3.22
3.14
3.08
3.24
3.22
3.15
2.07
3.26
3.24
3.17
1.06
3.28
3.26
0.00
0.00
3.30
3.28
0.00
0.00
3.33
3.31
0.00
0.00
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Table 10. Duncan’s multiple range test for number of branches/plant in 10 readings.
Measur
ement
Experi
mental
site
Kileikis
1
Aba
Humra
Kileikis
2
Aba
Humra
Kileikis
3
Aba
Humra
Kileikis
4
Aba
Humra
Means
1.49
1.44
1.39
1.52
1.46
1.40
1.55
1.48
1.41
1.58
1.50
1.43
Acacia nilotica
Experi
Duncan
C.V
mental
groupin
treat.
g
A
A
A
A
A
A
A
A
A
A
A
A
5.20
4.20
8.23
10.38
Acacia tortilis
Means
T1
1.53
T2
T3
1.50
1.40
T4
1.34
T1
1.55
T2
T3
1.52
1.42
T4
1.36
T1
1.57
T2
T3
1.54
1.44
T4
1.37
T1
1.59
T2
T3
1.57
1.47
T4
1.38
Duncan
groupin
g
A
B
CB
Experi
mental
site
Means
Kileikis
1.47
Aba
Humra
1.43
1.41
Duncan
groupin
g
A
A
A
C.V
Experimental
treat.
Means
5.67
T1
1.52
T2
T3
1.49
1.39
A
B
CB
T4
1.33
C
T1
1.54
T2
T3
1.52
1.42
A
B
CB
T4
1.35
C
T1
1.56
T2
T3
1.53
1.43
A
BA
BA
T4
1.36
B
T1
1.58
T2
T3
1.56
1.46
A
A
A
T4
1.38
A
C
A
B
CB
Kileikis
1.50
Aba
Humra
1.45
1.42
A
A
A
4.73
C
A
BA
BA
Kileikis
1.52
Aba
Humra
1.47
1.43
A
A
A
8.81
B
A
A
A
A
159
Kileikis
1.57
Aba
Humra
1.48
1.44
A
A
A
9.91
Duncan
grouping
Table 10 cont.
5
6
7
8
9
10
Kileikis
Aba
Humra
1.61
1.52
1.44
A
A
A
Kileikis
Aba
Humra
1.64
1.54
1.12
A
A
A
Kileikis
Aba
Humra
1.65
1.21
1.13
A
BA
B
Kileikis
Aba
Humra
1.30
1.22
0.76
A
A
A
Kileikis
Aba
Humra
0.90
0.84
0.78
A
A
A
Kileikis
Aba
Humra
0.92
0.85
0.79
A
A
A
13.48
16.73
18.19
19.93
8.47
8.99
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
1.61
1.58
1.49
1.40
1.63
1.61
1.52
0.98
1.65
1.63
1.54
0.48
1.67
1.65
0.00
0.00
1.69
1.67
0.00
0.00
1.72
1.70
0.00
0.00
A
BA
B
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
160
1.59
1.50
1.45
Kileikis
Aba
Humra
A
A
A
1.61
1.50
1.13
Kileikis
Aba
Humra
A
A
B
1.64
1.20
1.14
Kileikis
Aba
Humra
A
BA
B
1.28
1.21
0.78
Kileikis
Aba
Humra
A
A
A
0.89
0.83
0.79
Kileikis
Aba
Humra
A
A
A
0.91
0.85
0.80
Kileikis
Aba
Humra
A
A
A
12.48
17.81
18.58
19.93
7.31
7.85
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
1.60
1.57
1.48
1.39
1.62
1.57
1.50
0.96
1.64
1.62
1.53
0.51
1.66
1.64
0.00
0.00
1.68
1.66
0.00
0.00
1.71
1.69
0.00
0.00
A
BA
B
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Table 11. Duncan’s multiple range test for plant moisture content in 10 readings.
Measur
ement
1
2
3
4
Experi
mental
site
Kileikis
Means
1.62
Acacia nilotica
Experi
Duncan
C.V
mental
groupin
treat.
g
A
T1
Aba
1.57
A
Humra
1.52
A
4.00
Acacia tortilis
1.60
Duncan
groupin
g
A
Aba
1.55
A
Humra
1.53
A
1.66
Duncan
groupin
g
A
Experi
mental
site
Kileikis
T2
1.63
B
T3
1.52
CB
T4
1.45
C
Means
Means
C.V
5.19
Experimental
treat.
T1
Means
Duncan
grouping
1.65
A
T2
1.62
B
T3
1.51
CB
T4
1.44
C
Kileikis
1.65
A
T1
1.68
A
Kileikis
1.62
A
T1
1.67
A
Aba
1.59
A
T2
1.65
B
Aba
1.57
A
T2
1.64
B
Humra
1.53
A
T3
1.54
B
Humra
1.54
A
T3
1.53
B
T4
1.47
B
T4
1.46
B
4.00
5.18
Kileikis
1.67
A
T1
1.70
A
Kileikis
1.65
A
T1
1.69
A
Aba
1.61
A
T2
1.67
A
Aba
1.59
A
T2
1.66
A
Humra
1.54
A
T3
1.36
A
Humra
1.55
A
T3
1.55
A
T4
1.49
A
T4
1.48
A
T1
1.72
A
T1
1.71
A
T2
1.68
A
T3
1.58
A
T4
1.50
A
Kileikis
1.70
A
Aba
1.63
A
Humra
1.55
B
6.23
9.31
Kileikis
1.68
A
T2
1.69
A
Aba
1.61
A
T3
1.59
A
Humra
1.56
B
T4
1.51
A
161
7.21
10.40
Table 11 cont.
5
6
7
8
9
10
Kileikis
Aba
Humra
1.73
1.05
1.65
A
A
B
Kileikis
Aba
Humra
1.76
1.67
1.22
A
A
B
Kileikis
Aba
Humra
1.79
1.30
1.22
A
BA
B
Kileikis
Aba
Humra
1.40
1.32
0.84
A
A
A
Kileikis
Aba
Humra
0.97
0.91
0.84
A
A
A
Kileikis
Aba
Humra
0.99
0.92
0.86
A
A
A
13.44
17.10
18.55
19.92
8.00
8.50
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
1.74
1.71
1.62
1.53
1.76
1.74
1.64
1.06
1.78
1.76
1.66
0.56
1.80
1.78
0.00
0.00
1.82
1.80
0.00
0.00
1.85
1.83
0.00
0.00
A
BA
B
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
162
Kileikis
Aba
Humra
1.71
1.63
1.58
A
A
B
Kileikis
Aba
Humra
1.74
1.65
1.22
A
A
B
Kileikis
Aba
Humra
1.77
1.29
1.23
A
BA
B
Kileikis
Aba
Humra
1.38
1.30
0.84
A
A
A
Kileikis
Aba
Humra
0.96
0.89
0.85
A
A
A
Kileikis
Aba
Humra
0.98
0.91
0.86
A
A
A
14.47
17.51
18.51
20.05
7.12
7.63
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
T1
T2
T3
T4
1.73
1.70
1.61
1.52
1.75
1.73
1.63
1.05
1.77
1.75
1.65
0.55
1.79
1.77
0.00
0.00
1.81
1.79
0.00
0.00
1.84
1.82
0.00
0.00
A
BA
B
B
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Table 12. Analysis of variance for (SMC), (SUR), (SL), (DCR), (NOB) and (PMC) in 10 reading successively.
Source
d.f
TRT
BLK
Error
2
3
6
TRT
BLK
Error
2
3
6
TRT
BLK
Error
2
3
6
TRT
BLK
Error
2
3
6
TRT
BLK
Error
2
3
6
SMC1
3.24**
1.30*
0.13
SUR1
SP1
1948.44**
855.00ns
71.22
SP2
1759.33**
660.08ns
64.86
SL1
SP1
103.98ns
77.123ns
42.47
SP2
139.593ns
90.283ns
60.489
SMC2
3.02**
1.34*
0.13
SUR2
SP1
SMC3
3.67**
2.48*
0.14
SUR3
SP1
1821.21**
1787.2**
ns
753.42
72.31
SP2
988.17ns
70.41
SP2
1658.4**
1609.9**
645.58ns
65.47
SL2
SP1
132.73**
32.1ns
11.42
SP2
103.13**
13.8ns
17.76
945.25ns
64.36
SL3
SP1
348.67ns
257.81ns
86.66
SP2
311.8ns
261.52ns
89.14
SMC4
3.73**
1.97**
0.04
SUR4
SP1
1654.2**
972.0ns
72.37
SP2
1560.1**
937.67ns
67.48
SL4
SP1
278.67ns
424.3ns
99.27
SP2
264.2ns
311.3ns
101.16
Mean square (MS)
SMC5
SMC6
**
3.33
2.99**
3.31**
5.45**
0.03
0.16
SUR5
SUR6
SP1
SP1
1536.2**
930.58*
892.25ns
682.75*
73.61
69.14
SP2
SP2
1428.1** 851.63*
789.17ns
599.08*
69.52
62.72
SL5
SL6
SP1
SP1
270.1ns
252.23ns
436.52ns 149.05**
100.11
44.97
SP2
SP2
282.09ns
252.64ns
314.77ns 147.67**
102.05
90.35
163
SMC7
1.28**
8.96**
0.96
SUR7
SP1
871.71*
632.08*
123.5
SP2
721.89*
603.89*
170.2
SL7
SP1
532.9ns
155.46ns
52.22
SP2
492.5ns
154,34ns
52.11
SMC8
3.62ns
12.88ns
13.92
SUR8
SP1
722.1ns
601.4ns
182.1
SP2
700.0ns
596.75ns
133.64
SL8
SP1
767.14ns
138.55ns
65.9
SP2
638.8ns
180.16ns
65.78
SMC9
3.60ns
12.96ns
13.92
SUR9
SP1
532.71ns
319.8ns
102.11
SP2
323.7ns
229.1ns
89.21
SL9
SP1
1426.48ns
541.31ns
180.44
SP2
1425.27ns
539.62ns
180.01
SMC10
0.18ns
0.56ns
0.140
SUR10
SP1
233.1ns
133.7ns
56.3
SP2
145.2ns
117.8ns
45.7
SL10
SP1
1428.74ns
539.89ns
180.53
SP2
1427.54ns
539.61ns
180.52
Table 12 cont.
TRT
BLK
Error
TRT
BLK
Error
TRT
BLK
Error
TRT
BLK
Error
TRT
BLK
Error
2
3
6
2
3
6
2
3
6
2
3
6
2
3
6
DCR1
SP1
0.272**
0.005ns
0.019
SP2
0.202**
0.003ns
0.016
NOB1
SP1
0.068**
0.002ns
0.004
SP2
0.026**
0.005ns
0.004
PMC1
SP1
0.068**
0.002ns
0.004
SP2
DCR2
SP1
0.265**
0.014ns
0.019
SP2
0.213**
0.013ns
0.017
NOB 2
SP1
0.0838**
0.003ns
0.004
SP2
0.022**
0.007ns
0.004
PMC 2
SP1
0.063**
0.007ns
0.005
SP2
DCR3
SP1
1.229ns
0.893ns
0.609
SP2
1.091ns
0.654ns
0.587
NOB 3
SP1
0.327ns
0.124ns
0.131
SP2
0.343ns
0.125ns
0.181
PMC 3
SP1
0.330ns
0.226ns
0.149
SP2
DCR4
SP1
1.533ns
5.340*
0.554
SP2
1.352ns
3.763*
0.572
NOB 4
SP1
0.484ns
0.595ns
0.195
SP2
0.404ns
0.575ns
PMC 4
SP1
0.269ns
0.959*
0.169
SP2
DCR5
SP1
1.577ns
4.642*
0.548
SP2
1.396ns
3.341*
0.570
NOB 5
SP1
0.555ns
0.605ns
0.163
SP2
0.493ns
0.610ns
0.163
PMC 5
SP1
0.439ns
1.209*
0.114
SP2
164
DCR6
SP1
1.328ns
6.681**
0.867
SP2
1.146ns
5.421**
0.870
NOB 6
SP1
0.357ns
2.381**
0.188
SP2
0.304ns
2.520**
0.188
PMC 6
SP1
0.333ns
2.716**
0.215
SP2
DCR7
SP1
3.881ns
6.429ns
1.524
SP2
3.522ns
3.384ns
1.582
NOB 7
SP1
0.913ns
1.434ns
0.339
SP2
0.959ns
1.304ns
0.377
PMC 7
SP1
0.964ns
1.584ns
0.367
SP2
DCR8
SP1
1.350ns
4.048ns
1.350
SP2
1.039ns
3.433ns
1.039
NOB 8
SP1
0.315ns
0.941ns
0.315
SP2
0.617ns
0.987ns
0.317
PMC 8
SP1
0.343ns
1.027ns
0.343
SP2
DCR9
SP1
1.354ns
4.060ns
1.354
SP2
1.379ns
4.161ns
1.339
NOB 9
SP1
0.315ns
0.941ns
0.315
SP2
0.317ns
0.941ns
0.317
PMC 9
SP1
0.339ns
1.015ns
0.339
SP2
DCR10
SP1
1.358ns
4.071ns
1.358
SP2
1.353ns
4.172ns
1.353
NOB 10
SP1
0.319ns
0.952ns
0.319
SP2
0.318ns
0.950ns
0.318
PMC 10
SP1
0.340ns
1.020ns
0.340
SP2
TRT
BLK
Error
2
3
6
0.029**
0.005ns
0.008
0.024**
0.008ns
0.005
0.312ns
0.266ns
0.101
0.270ns
0.946*
0.145
0.466ns
1.234*
0.101
165
0.332ns
2.557**
0.227
0.996ns
1.278ns
0.337
0.347ns
1.010ns
0.347
0.323ns
1.127ns
0.323
0.340ns
1.019ns
0.340
Table 12 cont.
TRT
BLK
TRT
BLK
TRT
BLK
TRT
BLK
TRT
BLK
TRT
BLK
TRT
BLK
SMC1
0.001**
0.013*
SUR1
SP1
0.0007**
0.3883ns
SP2
0.0029**
0.1180ns
SMC2
0.001**
0.012*
SUR2
SP1
0.0008**
0.3883ns
SP2
0.0020**
0.127ns
SMC3
0.0008**
0.0033**
SUR3
SP1
0.0009**
0.051ns
SP2
0.0029**
0.3883ns
SMC4
0.0001**
0.0062**
SUR4
SP1
0.0038**
0.061ns
SP2
0.0029**
0.3883ns
SMC5
0.0001**
0.0001**
SUR5
SP1
0.0036**
0.138ns
SP2
0.0029**
0.072ns
SMC6
0.0025**
0.0005**
SUR6
SP1
0.0212*
0.0301*
SP2
0.0379*
0.421*
SMC7
0.0029**
0.0004**
SUR7
SP1
0.031*
0.029*
SP2
0.032*
0.013*
SMC8
0.4547ns
0.3190ns
SUR8
SP1
0.252ns
0.4542ns
SP2
0.158ns
0.127ns
SMC9
0.4547ns
0.3250ns
SUR9
SP1
0.125ns
0.4547ns
SP2
0.1293ns
0.062ns
SMC10
0.3784ns
0.0931ns
SUR10
SP1
0.125ns
0.4542ns
SP2
0.1787ns
0.073ns
SL1
SL2
SL3
SL4
SL5
SL6
SL7
SL8
SL9
SL10
SP1
0.077ns
0.223ns
SP2
0.061ns
0.298ns
DCR1
SP1
0.001**
0.223ns
SP2
0.004**
0.693ns
SP1
0.001**
0.234ns
SP2
0.007**
0.371ns
DCR2
SP1
0.001**
0.332ns
SP2
0.004**
0.510ns
SP1
0.072ns
0.0426ns
SP2
0.069ns
0.127ns
DCR3
SP1
0.213ns
0.458ns
SP2
0.303ns
0.426ns
SP1
0.078ns
0.222ns
SP2
0.073ns
0.134ns
DCR4
SP1
0.134ns
0.021*
SP2
0.213ns
0.034*
SP1
0. 062ns
0. 214ns
SP2
0. 071ns
0.134ns
DCR5
SP1
0.125ns
0.018*
SP2
0.187ns
0.015*
SP1
0.162ns
0.006**
SP2
0.161ns
0.001**
DCR6
SP1
0.369ns
0.007**
SP2
0.366ns
0.001**
SP1
0.116ns
0.094ns
SP2
0.126ns
0.061ns
DCR7
SP1
0.152ns
0.072ns
SP2
0.132ns
0.057ns
SP1
0.455ns
0.128ns
SP2
0.455ns
0.126ns
DCR8
SP1
0.455ns
0.129ns
SP2
0.343ns
0.137ns
SP1
0.455ns
0.126ns
SP2
0.455ns
0.126ns
DCR9
SP1
0.455ns
0.125ns
SP2
0.454ns
0.128ns
SP1
0.455ns
0.126ns
SP2
0.455ns
0.126ns
DCR10
SP1
0.455ns
0.125ns
SP2
0.448ns
0.128ns
166
Table 12 cont.
TRT
BLK
TRT
BLK
TRT
BLK
TRT
BLK
NOB1
SP1
0.003**
0.619ns
SP2
0.001**
0.416ns
PMC1
SP1
0.003**
0.619ns
SP2
0.004**
0.477ns
NOB 2
SP1
0.002**
0.568ns
SP2
0.001**
0.443ns
PMC 2
SP1
0.004**
0.477ns
SP2
0.006**
0.568ns
NOB 3
SP1
0.157ns
0.441ns
SP2
0.125ns
0.431ns
PMC 3
SP1
0.008**
0.442ns
SP2
0.186ns
0.292ns
NOB 4
SP1
0.115ns
0.599ns
SP2
0.132ns
0.105ns
PMC 4
SP1
0.191ns
0.266ns
SP2
0.288ns
0.041*
NOB 5
SP1
0.095ns
0.089ns
SP2
0.072ns
0.092ns
PMC 5
SP1
0.280ns
0.032*
SP2
0.076ns
0.010*
Sp1 : Acacia nilotica
Sp2 : Acacia tortilis
SMC: soil moisture content
SUR: survival
SL : shoot length
DCR: diameter at collar
NOB: number of branches
PMC: plant moisture content
**: Significant at (P ≤ 0.01)
* : Significant at (P ≤ 0.05)
ns: not significant
167
NOB 6
SP1
0.230ns
0.007**
SP2
0.258ns
0.002**
PMC 6
SP1
0.057ns
0.010*
SP2
0.230ns
0.007**
NOB 7
SP1
0.139ns
0.072ns
SP2
0.140ns
0.097ns
PMC 7
SP1
0.238ns
0.002**
SP2
0.139ns
0.071ns
NOB 8
SP1
0.455ns
0.126ns
SP2
0.440ns
0.125ns
PMC 8
SP1
0.125ns
0.050ns
SP2
0.455ns
0.125ns
NOB 9
SP1
0.455ns
0.126ns
SP2
0.445ns
0.125ns
PMC 9
SP1
0.455ns
0.125ns
SP2
0.455ns
0.125ns
NOB 10
SP1
0.455ns
0.129ns
SP2
0.445ns
0.125ns
PMC 10
SP1
0.455ns
0.125ns
SP2
0.455ns
0.125ns
168