Assembling and Performance Evaluation of Centre Pivot Irrigation System New Hamdab Irrigation Project Northern State, Sudan

ASSEMBLING AND PERFORMANCE EVALUATION OF CENTRE PIVOT IRRIGATION SYSTEM NEW HAMDAB IRRIGATION PROJECT NORTHERN STATE, SUDAN

By Zuhair Abdalmalik Elhassan B.Sc. (Agric.) Honours University of Khartoum 1999

A Thesis Submitted to the University of Khartoum in partial Fulfillment for the requirement of the Degree of Master of Science in agriculture

Supervisor: Dr. Amir Bakheit Saeed

Dept. of Agricultural Engineering Faculty of Agriculture University of Khartoum

April 2008

1 TABLE OF CONTENTS

Page TABLE OF CONTENTS i LIST OF TABLES iii LIST OF FIGURES iv LIST OF PLATES v LIST OF MAPS vii DEDICATION viii ACKNOWLEDGEMENT ix ABSTRACT x ARABIC ABSTRACT xi CHAPTER ONE: INTRODUCTION 1 CHAPTER TWO: LITERATURE REVIEW 3 2.1 Irrigation methods 3 2.1.2 Sub-irrigation system 3 2.1.1 Surface irrigation systems 3 2.1.3 Drip (trickle) irrigation system 4 2.1.4 Sprinkler (overhead) irrigation systems 4 4 2.1.4.1 Advantage of sprinkler irrigation systems 5 2.1.4.2 Disadvantage of sprinkler irrigation systems 5 2.2 Sprinkler system classification 2.2.1 Permanent system 6 6 2.2.2 Semi-permanent system

2 6 2.2.3 Portable systems 6 2.3 Centre pivot irrigation system 2.3.1 Centre pivot with corner attachment 8 2.3.2 Linear move irrigation system 8 9 2.4 System performance 10 2.4.1 The uniformity coefficient (CU) 12 2.4.2 Distribution uniformity or pattern efficiency (DU) 12 2.4.3 Application efficiency (Ea%) 13 2.5 Irrigated agriculture in Sudan 13 2.6 Future prospects of modern irrigation CHAPTER THREE: MATERIALS AND METHODS 18 3.1 Prelude 18 21 3.2 Pivot assembly 36 3.3 Hydraulic performance 3.3.1 Uniformity coefficient (CU) 47 47 3.3.2 Distribution uniformity or pattern efficiency (DU) 47 3.3.3 Application efficiency (Ea%) 48 3.3.4 Overall Irrigation efficiency 48 3.3.5Percentage of loss in the cultivable area

3 50 3.4 Irrigation water measurements 50 3.5 Measurement of irrigation water at centre pivot system 51 3.6 Plant parameters 51 3.6.1 Plant height (cm) 51 3.6.2 Crop density 51 3.6.3 Number of tillers 51 3.6.4 Spike length 51 3.6.5 Number of seeds/spike 51 3.6.6 Weight of 1000 grain 51 3.6.7 Stem thickness CHAPTER FOUR: RESULTS AND DISCUSSION 52 4.1 Technical performance 52 52 4.1.1 Uniformity coefficient 53 4.1.2 Uniformity distribution (DU) 54 4.1.3 Application efficiency (Ea%) 4.2 Plant parameters 55 4.2.1 Plant density, number of leaves, leaf area index, stem size 55 and plant height 4.2.2 Weight of 1000 grain, number of seeds/plant and 61 yield(kg/fd)

CHAPTER FIVE:CONCLUSIONS AND 70 RECOMMENDATIONS 5.1 Conclusions 70 5.2 Recommendations 70 REFERENCES 72 APPENDICES 75

LIST OF TABLES . Table Title Page

2.1 Agricultural Activities in Sudan 15 3.1 Climate data from Karima metreological station (1941-1970) 19 4.1 Plant density (Number of plants/m2) 56

4.2 Number of leaves per plant 56

4.3 Leaf area index (mm2) 56

4.4 Stem size (mm) 57

4.5 Plant height (cm) 57

4.6 Weight of 1000 grain (gm) 62

4.7 Number of seeds per plant 62

4.8 Yield (kg/fd) 62

4.9 Amount of water applied per feddan (m3/fed) 62

4.10 Center pivot at 100% speed 63

4.11 Center pivot at 40% speed 66

LIST OF FIGURS

Fig Title Page

3.1 Concrete pad with 4 anchor bolts 27

3.2 Drop pipe and sprinkler 29

4.1 Center pivot at 100% speed 65

4.2 Center pivot at 40% speed 68

7 LIST OF PLATES

Plate Title Page

3.1 A boom truck and nylon strap 22

3.2 Center pivot complete package 24

3.3 Center pivot concrete pad and trench 25

3.4 Center pivot head fixed to its legs 26

3.5 The pipes are laid and bolted together 28

3.6 The pipes of span 30

3.7 Complete span 31

3.8 Weldment connected to pivot 32

3.9 Towing wheel 33

3.10 Rubber hose with clamps 34

3.11 Collector ring 35

3.12 Diesel engine with single stage pump 37

3.13 Diesel engine with double stage pump 38

3.14 Suction basin 39

3.15 PVC pipes (∅ 9″) 40

3.16 Zee pipe from single stage pump 41

3.17 Zee pipe from double stage pump 42

8 Plate Title Page

3.18 Flow meter 43

3.19 Pressure gauge 44

3.20 Catch cans 45

3.21 Water measurement 46

3.22 Wheel track 49

4.1 Wheat under center pivot 58

4.2 Wheat in the pilot farm (surface irrigation) 59

4.3 Wheat in the tenant farm (surface irrigation) 60

5.1 Potato under center pivot 72

LIST OF MAPS

Map Title Page

3.1 New Hamadab agricultural project 20

This work is dedicated,

To my Father Mother,

Brothers

Sisters

& all my friends

11 ACKNOWLEDGMENT

My praise be to Allah, who gave me health to complete this work, also I would like to express my sincere gratitude and thanks to my supervisor Dr. Amir Bakheit Saeed for his guidance, encouragement and help to carry out this work. Finally, I would like to express deep thanks to all those who gave me help during the progress of this work particularly Dr. Ali Widaa, Eng. Abdulbagi Abuagla, Eng. Khalid Mubashar , Shaza Alrayeh & Miss Bilghies.

Zuhair

12 ABSTRACT This study was conducted at new Hamdab agricultural project, one of the newly established resettlement projects associated with the implementation of Merowi Dam. The project lies on the western bank of the River Nile in the Northern state about 300 km north of Omdurman. Following the innovation technologies in the irrigation systems world wide, this study has come to make a comparison between modern irrigation systems and traditional ones in aspects of operation costs, irrigation water requirement and expected yield. The study comprised an updated comprehensive survey on the centre pivot systems introduced in Sudan; then assembling five Zimmatic centre pivot systems on predetermined locations on the sandy area (high terrace) of new Hamdab project. The systems were then evaluated for hydraulic performance namely, uniformity coefficient (Cu), distribution uniformity (Du) and application efficiency (Ea). The centre pivot system was then compared with surface irrigated field plots (pilot farm) while considering the traditional method (tenant field) as a control and wheat as an indicator crop. The centre pivot system wwhen run at two speeds (40% and 100%) respectively gave the following results: 1- Uniformity coefficient (Cu) 75% and 85%. 2- Distribution uniformity (Du) 60% and 76%. 3- Application efficiency (Ea) 53% and 47%. . With respect to wheat growth parameters and yield attributes, the centre pivot irrigation system showed highly significant difference over the pilot farm and the tenant farms, the average productivities of wheat per feddan were respectively: 1532 kg, 464kg, 159 kg for center pivot, pilot farm and tenant farm.

13 On the other hand records of water consumed per feddan per season were 5344 m3 for the centre pivot and 9306 m3 for either one of pilot farm and tenant’s farm. The study clearly shows that center pivot irrigation system has gave prospects particularly in the high terrace soils in north Sudan.

14 اﻟﺨﻼﺻﺔ اﺟﺮﻳﺖ هﺬﻩ اﻟﺪراﺳﻪ ﻓﻲ ﻣﺸﺮوع اﻟﺤﺎﻣﺪاب اﻟﺠﺪﻳﺪة اﻟﺰراﻋﻲ ، اﺣﺪ ﻣﺸﺎرﻳﻊ اﻋﺎدة اﻟﺘﻮﻃﻴﻦ اﻟﺠﺪﻳﺪة اﻟﻤﺼﺎﺣﺒﺔ ﺳﺪ ﻣﺮوي. ﻳﻘﻊ اﻟﻤﺸﺮوع ﻋﻠﻰ اﻟﺠﺎﻧﺐ اﻟﻐﺮﺑﻲ ﻟﻨﻬﺮ اﻟﻨﻴﻞ ﻓﻲ اﻟﻮﻻﻳﺔ اﻟﺸﻤﺎﻟﻴﺔ وﻳﺒﻌﺪ ﺑﺤﻮاﻟﻰ 300 آﻠﻢ ﺷﻤﺎل أم درﻣﺎن. ﻣﻮاآﺒﺔ ﻟﻠﺘﻄﻮر اﻟﻌﺎﻟﻤﻲ ﻓﻲ ﻧﻈﻢ اﻟﺮي اﻟﺤﺪﻳﺜﺔ ﺟﺎءت هﺬﻩ اﻟﺘﺠﺮﺑﺔ ﻟﺘﻮﻃﻴﻦ ﺗﻘﺎﻧﺔ اﻟﺮي اﺣﺪﻳﺜﺔ ﻓﻲ اﻟﺴﻮدان ﺑﻌﺪ ﻣﻘﺎرﻧﺘﻬﺎ ﻣﻊ اﻟﻨﻈﻢ اﻟﺘﻘﻠﻴﺪﻳﻪ اﻟﺴﺎﺋﺪﻩ ﻣﻦ ﺣﻴﺚ ﺗﻜﻠﻔﺔ اﻟﺘﺸﻐﻴﻞ، آﻤﻴﺔ ﻣﻴﺎﻩ اﻟﺮي اﻟﻤﺴﺘﺨﺪﻣﻪ واﻻﻧﺘﺎﺟﻴﺔ اﻟﻤﺘﻮﻗﻌﺔ. هﺪﻓﺖ اﻟﺪراﺳﺔ ﻻﺟﺮاء ﻣﺴﺢ ﺷﺎﻣﻞ ﻋﻠﻰ ﻧﻈﻢ اﻟﺮي اﻟﻤﺤﻮري ﻓﻲ اﻟﺴﻮدان و ﺗﺮآﻴﺐ ﻋﺪد ﺧﻤﺴﺔ أﺟﻬﺰة ري ﻣﺤﻮري ﻣﺎرآﺔ (زﻳﻤﺘﻴﻚ)ﻋﻠﻰ ﻣﻮاﻗﻊ ﻣﺤﺪدة ﺳﻠﻔﺎ ﻋﻠﻰ اراﺿﻲ رﻣﻠﻴﺔ (ﺗﺮوس ﻋﻠﻴﺎ) ﻟﻤﺸﺮوع اﻟﺤﺎﻣﺪاب اﻟﺠﺪﻳﺪة و ﺗﻘﻴﻴﻢ ﺑﻌﺾ اﻟﺨﺼﺎﺋﺺ اﻟﻬﻴﺪروﻟﻴﻜﻴﻪ وﺑﺤﺴﺎب ﻣﻌﺎﻣﻞ اﻟﺘﻮزﻳﻊ(Cu) ، اﻧﺘﻈﺎﻣﻴﺔ اﻟﺘﻮزﻳﻊ (Du) وآﻔﺎءﻩ اﻻﺿﺎﻓﺔ (Ea) ﻻﺟﻬﺰة اﻟﺮي اﻟﻤﺤﻮري. ﺗﻤﺖ ﻣﻘﺎرﻧﺔ ﻧﻈﺎم اﻟﺮي اﻟﻤﺤﻮري ﺑﻨﻈﺎم اﻟﺮي اﻟﺴﻄﺤﻲ اﻟﻤﺘﺒﻊ ﻓﻲ ﻣﺰرﻋﺔ ﺗﺠﺮﻳﺒﻴﺔ ﺑﺎﻟﻤﺸﺮوع واﻋﺘﺒﺎر اﻟﻤﺰارع اﻟﺘﻘﻠﻴﺪﻳﺔ ﻟﻠﻤﺰارﻋﻴﻦ آﻤﺮﺟﻊ ﻣﻊ اﻋﺘﺒﺎر ﻣﺤﺼﻮل اﻟﻘﻤﺢ ﻓﻲ هﺬﻩ اﻟﻤﻮاﻗﻊ ﻣﺤﺼﻮﻵ ﻣﺆﺷﺮﺁ ﻟﻠﺘﺠﺎرب. ﺗﻢ اﺧﺘﻴﺎر اﺣﺪ هﺬﻩ اﻻﺟﻬﺰﻩ اﻟﺨﻤﺲ ﺑﻌﺪ اآﻤﺎل ﻋﻤﻠﻴﺔ اﻟﺘﺮآﻴﺐ و ﺗﺸﻐﻴﻠﻪ ﺑﺎﻟﺴﺮﻋﺘﻴﻦ اﻟﻘﻴﺎﺳﻴﺘﻴﻦ 40 ٪ و 100 ٪ ﻋﻠﻰ اﻟﺘﻮاﻟﻲ وآﺎﻧﺖ ﻧﺘﺎﺋﺞ اﻟﺨﺼﺎﺋﺺ اﻟﻬﻴﺪروﻟﻴﻜﻴﺔ ﻋﻠﻲ اﻟﺘﻮاﻟﻲ آﺎﻻﺗﻲ: 1- ﻣﻌﺎﻣﻞ اﻟﺘﻮزﻳﻊ (Cu) 75 ٪ و 85 ٪ . 2- إﻧﺘﻈﺎﻣﻴﺔ اﻟﺘﻮزﻳﻊ (Du) 60 ٪ و 76 ٪. 3- آﻔﺎءة اﻟﺘﻮزﻳﻊ (Ea) آﺎﻧﺖ 53 ٪ و 47 ٪. ﻣﻘﺎرﻧﺔ ﻋﻮاﻣﻞ اﻟﻨﻤﻮ واﻹﻧﺘﺎﺟﻴﺔ ﻟﻠﻘﻤﺢ ﺑﺎﻟﺮي اﻟﻤﺤﻮري ﻣﻊ آﻞ ﻣﻦ اﻟﻤﺰارع اﻟﺘﺠﺮﻳﺒﻴﺔ واﻟﺘﻘﻠﻴﺪﻳﺔ أﻇﻬﺮت ﻓﺮوﻗﺎ ﻣﻌﻨﻮﻳﺔ ﻋﺎﻟﻴﺔ ﻟﻠﺮي اﻟﻤﺤﻮري ﻋﻠﻲ اﻟﻤﺰراع اﻟﺘﺠﺮﻳﺒﻴﺔ واﻟﺘﻘﻠﻴﺪﻳﺔ، وآﺎﻧﺖ اﻧﺘﺎﺟﻴﺔ ﻓﺪان اﻟﻘﻤﺢ ﻋﻠﻲ اﻟﺘﻮاﻟﻲ آﺎﻟﺘﺎﻟﻲ : 1- اﻟﺮي اﻟﻤﺤﻮري 1532 آﺠﻢ . 2- اﻟﻤﺰارع اﻟﺘﺠﺮﻳﺒﻴﺔ 464 آﺠﻢ . 3- اﻟﻤﺰارع اﻟﺘﻘﻠﻴﺪﻳﺔ 159 آﺠﻢ . وﻣﻦ ﻧﺎﺣﻴﺔ أﺧﺮى ﺗﻢ ﺗﺴﺠﻴﻞ آﻤﻴﺎت اﻟﻤﻴﺎﻩ اﻟﻤﺴﺘﻬﻠﻜﺔ ﻓﻰ اﻟﻤﻮﺳﻢ ﻟﻠﻔﺪان وآﺎﻧﺖ 5344 ﻣﺘﺮ ﻣﻜﻌﺐ ﻟﻠﺮى اﻟﻤﺤﻮرى،9306 ﻣﺘﺮ ﻣﻜﻌﺐ ﻟﻜﻞ ﻣﻦ اﻟﻤﺰارع اﻟﺘﺠﺮﻳﺒﻴﺔ واﻟﺘﻘﻠﻴﺪﻳﺔ. ﻣﻤﺎ ﺳﺒﻖ ﺗﺘﻀﺢ ﻣﻼءﻣﺔ اﻟﺮى اﻟﻤﺤﻮرى ﻟﻈﺮوف اﻟﺴﻮدان ﺧﺎﺻﺔ ﻓﻰ أراﺿﻰ اﻟﺘﺮوس اﻟﻌﻠﻴﺎ ﻓﻴﻤﺎ ﻳﺘﻌﻠﻖ ﺑﺰﻳﺎدة اﻻﻧﺘﺎج وﺗﺤﺴﻴﻦ ﻧﻮﻋﻴﺘﻪ ﻣﻘﺎرﻧﺔ ﺑﺎﻟﻨﻈﻢ اﻟﺘﻘﻠﻴﺪﻳﺔ.

15 CHAPTER ONE INTRODUCTION

Irrigation is the artificial application of water to the soil for the purpose of crop production. Irrigation water is applied to supplement the water available from rainfall and the contribution to soil moisture from the ground water. In many areas of the world, the amount and timing of rainfall are not adequate to meet the moisture requirement of crops and irrigation is essential to raise crops necessary to meet the needs of food and fiber. The major constraints to produce more food to meet the increasing demands of the world population are land and water. One possible approach to conserve these scarce resources may be through improving the performance of the existing irrigation projects. Sudan is mainly an agricultural country rich with natural resources that need to be utilized efficiently for self-sufficiency and with excess for export. Water resources in Sudan are mainly from rain, rivers, seasonal streams and under ground aquifers, while the Nile and its tributaries are considered the main conventional source of water for reliable agricultural development. The distribution of water obtained from the Nile and its tributaries is governed by two main bilateral agreements between Sudan and Egypt signed in 1929 and 1959. According to the 1959 agreement Sudan is allotted an annual share of 18.5 milliards m3 as measured at Aswan. Additional supplies of water can be available through water conservation projects such as the Jongli canal, which if completed could have saved about four milliards m3 annually to be shared equally between Sudan and Egypt.

16 The application of improved and /or modernized irrigation methods and techniques is expanding rapidly in Sudan as a result of the increasing demand for higher irrigation efficiency. This will save large quantities of water, which would have otherwise been lost through evaporation, run off and deep percolation in the conveyance network or at the on farm level. The overhead (sprinkler) irrigation systems gains preference or adaptability in most topographic conditions without extensive land preparation and also because of their flexible components and efficient control of water application. The centre pivot is a moving irrigation system with a lateral that rotates around a fixed (pivot) point. The system was first patented in 1952 as described by Pair et al. (1975). Use of centre pivot systems has grown rapidly in recent years because of their low labor requirement, in addition to their capabilities of time with minimum supervision. The objectives of this study include the following. 1. Assembling of preselected centre pivot irrigation systems in a newly established irrigation project. 2. Evaluation of the system performance a) Hydraulically (coefficient of uniformity and distribution uniformity). b) in relation to conventional irrigation system (crop growth parameter and yield component attribute

17 CHAPTER TWO LITERATURE REVIEW

Irrigation historically has played and will continue to play a critical role in agricultural development. It supplies the water needed for crop growth when rainfall is limited. The increasing need for crop production for growing population is causing rapid expansion of irrigation throughout the world. The global irrigated area increased from about 40 million hectares in 1965 to about 241.6 million hectares in 1991 (FAO, 1993).

2.1 Irrigation methods The four basic methods of irrigation are surface or gravity irrigation, sub-surface irrigation (sub-irrigation, which may use tile drain lines), trickle irrigation and sprinkler irrigation (Scherer, 1998).

2.1.1 Surface irrigation systems In the surface method of irrigation, water is applied directly to the soil from a channel located at the upper reach of the field. Water may be distributed to the crops by border strip, check basin or furrows.

2.1.2 Sub-irrigation system Water is applied below the ground surface. Water reaches the roots through the capillary action. Water may be introduced through open ditches or underground pipeline (Michael, 1978).

18 2.1.3 Drip (trickle) irrigation system Is one of the latest methods of irrigation, which is becoming increasingly popular in areas with water scarcity and salt problems. It is a method of watering plants frequently and with a volume of water approaching the consumptive use of the plant and would minimize such conventional losses as deep percolation, runoff and soil water evaporation (Michael, 1978)

2.1.4 Sprinkler (overhead) irrigation systems Is the method of applying water to the surface of the soil in the form of spray, somewhat as in ordinary rain. This method of irrigation was started about 1900. The first agricultural sprinkler systems were an out growth of city lawn sprinkling. Before 1920 sprinkling was limited to truck crops, nurseries and orchards (Israelsen et al., 1967). A sprinkler “throws” water through the air in an effort to simulate rainfall whereas the other three irrigation methods apply water directly to the soil, either on or below the surface (Scherer, 1998).

2.1.4.1 Advantage of sprinkler irrigation systems 1. Land with irregular topography can be irrigated with minimum leveling and disturbance of the topsoil. The same applies to shallow soils. 2. On sloping lands runoff and soil erosion that usually accompany surface irrigation can be eliminated. 3. Sandy or other highly permeable soils can be irrigated without excessive losses by deep percolation, thrust reducing the danger of creating drainage problems. 4. Field ditches are not necessary. Thus, increasing the area available for crop production and eliminating the problem of ditch maintenance.

19 5. Where the available water supply is a small continuous stream, greater efficiency in both water and labor will result when the water is applied using sprinkler irrigation methods. 6. The sprinkler irrigation method is well adapted to light applications of water for the purpose of seed bed preparation, seed germination and transplanting and thinning of seedlings (FAO, 1960).

2.1.4.2 Disadvantage of sprinkler irrigation systems 1. High initial costs of the equipment. 2. Operating costs usually are higher than for irrigating by surface methods. 3. Irrigation using sprinkler is not well adapted to conditions where water supply is available intermittently. Unless, the sprinkler system can be operated almost continuously, the investment in equipment may become as high as to make its use prohibitive. 4. Moving the portable lines when the soil (especially heavy clay) is soft and wet is an unfavorable task. 5. Mechanical difficulties must be expected: sprinkler fail to rotate, nozzle may get clogged, couplers may leak, or the engine may require attention (FAO, 1960).

2.2 Sprinkler system classification The sprinkler systems are classified as permanent, semi permanent (semi-portable), portable set move and solid set or continuous move systems (James, 1988).

2.2.1 Permanent system A fully permanent system has buried main line, sub-main and laterals with stationary pumping plant and/or water source. As

20 Sprinkler head (or nozzles) is permanently located on each riser (James, 1988).

2.2.2 Semi-permanent system Have portable lateral line, permanent main line and stationary water source and pumping plant. The main line is usually buried. The risers are located at suitable intervals on the laterals (James, 1988).

2.2.3 Portable systems The fully portable system has portable lateral pipelines with sprinklers and a portable pumping plant (FAO, 1960).

2.3 Centre pivot irrigation system The centre pivot has at times been referred to as the most significant piece of technology to change the face of agriculture since the invention of the tractor. Its ability to irrigate “hilly” terrain and irregular shaped fields has greatly influenced the development of land in arid climates and increased the ability to produce, even in dry years (Valley-Standard, 1998). The centre pivot was so named because of its radial rotation around a centre point. The centre point is called the pivot (Valley-Standard, 1998). This self-propelled sprinkler system rotates around the pivot point and has the lowest labor requirements of the systems considered. It is constructed using a span of pipe connected to movable towers. It irrigates approximately 125.5 hectares (299 fed) or more out of a square quarter section. Centre pivot systems are either electric, water, or oil-drive and can handle slopes up to 15 percent. Sprinkler packages are available for low to high operating pressures (55 to 80 psi) at pivot point. Sprinkler can be mounted on top of the spans or on drop-tubes, which put them closer to the crop. The water application is controlled by the speed of

21 rotation Scheres (1998) and James (1988) reported that the depth of water applied by centre pivot system is determined by the speed at which the lateral rotates around the field. The maximum hour per revolution to prevent runoff can be estimated by the following equation suggested by James: 24 , Dm Sr ≤ 2.1 DDIR Where: Sr = Rotational speed of centre pivot lateral (h/revolution). Dm = Depth of water that can be applied per irrigation without runoff (mm/day). DDIR = Design of daily irrigation requirement (mm/day). Centre pivots are adaptable to any crop heights and are particularly suited to lighter soils. They are generally not recommended for heavy soils with low infiltration rates. Deep wheel tracks can be a problem on some soils, but there are a number of management methods available to control this problem. Electric drive pivots are the most popular due to flexibility of operation. Computerized control panel allows the operator to specify speed changes at any place in the field, reverse the pivot turns on auxiliary pumps at specified time and many other features (James, 1988). 2.3.1 Centre pivot with corner attachment Corner attachment systems are available, which allow irrigation of most corner areas missed by a conventional centre pivot system. Depending on the method of corner irrigation, pivot systems with corner attachments will irrigate 124 to 172.5 feddan out of 193.6 feddan quarter section. The most common method of corner irrigation has an additional span, complete with tower, attached to the end of the centre pivot systems main line, which swings out in the corners. As it

22 swings out, sprinkler is turned on to irrigate the corner. The movement of the moving span is controlled either by a buried wire or mechanical switch (Scherer, 1998). Another type of corner system uses several guns mounted on the end of the centre pivot system main line. The guns are activated in sequence from smallest to largest and back again as the machine moves past the corner (Scherer, 1998).

2.3.2 Linear move irrigation system The linear move (sometimes called a lateral move) irrigation system is built the same way as a centre pivot with moving towers and spans of pipe connecting the towers. The main difference is that all the towers move at the same speed and in the same direction. Water is pumped into either one of the ends or into the centre. Water can be supplied to the linear system either through a canal, by dragging a supply hoses, which is connected to a main line, or by connecting and disconnecting from hydrants as the linear moves down the field. The lateral movement makes it difficult to power a linear move sufficient with electricity. Usually, a diesel motor with a generator is mounted on the main drive tower and supplies the power needed to operate the irrigation system. The primary advantage of the linear is that it can irrigate rectangular fields up to a 625 m along and 312.5 m wide. Due to the high capital investment cost, linear are used on high value crops such as potatoes, and other vegetables (Scherer, 1998).

2.4 System performance Operating an irrigation system differently than assumed in the design will alter the application rate, uniformity of coverage, and subsequently the application uniformity.

23 Uniformity is how evenly the sprinkler package delivers water over the ground (Zoldoske et al., 1997). This is important to know because uneven or non uniform systems cerates areas those are either too wet or too dry. This non-uniformity causes havoc with irrigation scheduling. For centre pivot uniformity which is the measure of the variation in the depth of applied water, is of greater importance than any of the other performance measures such as efficiency (Heerman et al., 1980). The uniformity of centre pivot is solely dependent upon the operating parameters and the hydraulic design of system. Uniformity coefficients from centre pivot should exceed 90%, a performance level with which sprinkler and machine manufacturers readily agree, but a level that is infrequently attained in field (Raine and Foley, 2002). The uniformity of centre pivot in US is also variable, value of the Heerman and Hein coefficient, CUHH ranged from 70% to 86%. Operating with excessive pressure results in smaller droplets, greater potential for drift, and accelerating wear of the sprinkler nozzles. Pump wear tends to reduce operating pressure and flow. With continued use, nozzle wear results in an increase in nozzle opening, which will increase the discharge rate, while decreasing the wetted diameter. Clogging of nozzles or crystallization of main lines can result in increased pump pressure but reduce operating pressure. An operating pressure below design pressure greatly reduces the coverage diameter and application uniformity (Evan et al., 1996). As stated by Evan et al. (1996) centre pivot and linear move irrigation systems can be evaluated by placing a row (transect) of spray cans parallel to the system. The distance between spray cans should not exceed 15 m, but 7.5 m or less is generally recommended. Uniformity coefficient, distribution uniformity (pattern efficiency), of

24 the centre pivot and linear move irrigation systems can be measured using spray cans as described by Evan et al. (1996).

2.4.1 The uniformity coefficient (CU) A measurable index of the degree of uniformity from any size sprinkler operating under a given condition has been developed and is known as uniformity coefficient. The measurement of uniformity most commonly used by the industry is the Christiansen’s coefficient of uniformity (CU) expressed as a percentage as stated by Zoldoske and Salomon (1988) as follows: D CU = (1 − ) × 100 2.2 M Where: CU = Christiansen’s coefficient of uniformity (%). D = Average absolute deviation from the mean application rate, (mm). M = Average application rate, (mm). There are three important features of the (CU) formula that should be recognized and considered when interpreting (CU) values. The first is that due to the absolute value used in determining (D), (CU) treats over and under-watering (relative to the mean value (M) equally. (D) may be thought of as an average “penalty” function – it assigns a penalty to each catchments of individual application amount. The penalties assigned to application amount are the same equally above and below the mean. Secondly, the computation of (D) assigns penalties in what is mathematically called “a linear fashion”. This means that the penalty assigned to each catchment’s is in direct proportion to the amount by which it deviates from the mean. The third feature of (CU) is that it is an average measurement. By

25 comparing the average absolute deviation (D) to the mean application (M), (CU) indicates on average how uniform the sprinkler pattern is. It can give no indication of how bad a particular localized area might be, or how large that critical area might be. There is no question that (CU) has been a valuable tool in the design and evaluation of sprinkler irrigation systems. But the three features of (CU) noted above have caused a discount in the significance of (CU). “Over — and under — watering should be treated the same, they say” large deviations from the mean are far more significant than small ones. The penalty should be more proportionate to its size as suggested by some researchers. Still others state, the average conditions are of no concern to us, as what is needed to be known in the critical area”. Christiansen’s (CU) has also, been criticized unfairly, it seems that it is possible for two very different sprinkler application pattern to result in the same (CU), while this observation is true, it is not really fair to criticize (CU) for this “defect”. This potential exists for any and all coefficients that have been or could be invented. This is an unavoidable consequence of trying to represent a whole array of values (all individual application amounts) by a single indicator value. This “defect” is a trade-off that is necessary if it is required to have the convenience of referring to a single performance indicator. In spite of these criticisms, and in spite of the development of computers, elegant statistical analysis, and numerous other formulae for uniformity measure, CU is still the single most used yardstick for water uniformity (Zoldoske and Salomon, 1988).

2.4.2 Distribution uniformity or pattern efficiency (DU) This method sort all data points in the overlap area and ranks them from low to high with the mean value for lowest (25) percent

26 (low quarter) divided by the mean value for the entire area. However, this method does not take into account the location of water value or any benefit, which might be derived from water values immediately adjacent to the low values (Zoldoske and Salomon, 1988). Distribution uniformity or pattern efficiency can therefore be stated in the following form: DU = Average low quarter caught in the cans × 100 2.3 Average depth caught in all cans Where: DU = Distribution Uniformity.

2.4.3 Application efficiency (Ea%) The application efficiency of the centre pivot irrigation systems is calculated using the average depth of application as monitored by the systems flow meter (wf) and the average depth of water caught in the spray cans (ws). Then the application efficiency (Ea%) is calculated using the following equations: ws Ea % = × 100 2.4 wf The irrigation methods used in most projects in Sudan (Gezira, New Halfa, Rahad, Suki …etc) is a combination of border and short furrows. The Gezira and Rahad have conducted irrigation trials and studies on long furrows, which were used in Rahad experimental fields and Kenana fields. Water for crops grown under irrigation is applied through different forms of surface irrigation. In pump irrigated schemes water is lifted to the ground surface by pumping and then conveyed to the field by the action of gravity, while in the other irrigated schemes water is directly diverted from dam’s reservoirs via a network of canals to the field.

27 2.5 Future prospects of modern irrigation The presence of topographic and soil type hindrances in the form of undulating lands, shallow soils, sandy soils of high permeability make surface irrigation methods for field crops very limited due to run off , deep percolation losses and high cost of leveling. On the other hand, modem irrigation systems will save area required for canals and ridges. Also, mechanized farm operation especially harvesting will be facilitated under modem irrigation methods (Pair et al., 1975). Development of agricultural production potential is a challenge that must be met to keep pace with the increasing population. Improved seed varieties, better cultural practices, better management and better processing methods are all essential. These coupled with the successful use of drip and sprinkler irrigation systems to develop new agricultural lands and to irrigate dry lands for increased production, have demonstrated one solution to the problem of increasing demand for food and fiber supplies. In this respect Sudan is considered as one of the largest countries, which has substantial potential for agricultural activities (Table 2.1) The use of modern irrigation systems is getting popularity in Sudan particularly centre pivot system Appendix (A) exhibits an up to date survey on the number, make and model of centre pivot systems introduced in Sudan. One of the biggest motives to switch to centre pivot irrigation is to save water. This is confirmed by Arns et al. (2005) who worked on rice and showed that with better management, a reduction of water usage can reach above 50% as compared to surface methods of irrigation. A yield of 4.5 t/ha was obtained for wheat under the centre pivot system as compared to an average yield of 2.5 t/ha normally obtained in the same area. This is considered as a very promising indication for expanding agricultural development

28 (horizontally and vertically) in the area by adopting centre pivot techniques (Saeed, 2001).

Table 2.1 Agricultural Activities in Sudan Agric. activity Area (million ha) Total Area of Sudan 250 Total cultivable area 84 Irrigated area 2 Mechanized rainfed area 6 Traditional rainfed 9 Natural pasture 39 Forests 64 Source: Ministry of Agriculture and Forestry (1997).

29 Hence, it is clear that centre pivot has a good opportunity to be adopted under Sudan condition. Osman (2002) studied the performance of centre pivot irrigation system in Elargam project, west Omdurman. The soil was sandy with moderate to high infiltration rates and a bulk density of 1.54g /cm3. The centre pivot system was run at two speeds 100% and 50% their respective application efficiencies were 86% and 89%, the uniformity coefficients were 48% and 81% where as the distribution efficiencies were relatively low at 77% and 70%. Alarki (2002) concentrated his study on the design and evaluation of sprinkler irrigation system in general. He ended up by providing a computer program, which give the most suitable specifications for the nozzles, laterals, mainline lengths and size of pump hydropower. Ali (2004) carried out performance evaluation on centre pivot at Ras Elwadi Scheme, River Nile state. For producing alfalfa (Lucerne) under sandy clay loam soil with bulk density 1.5 g/cm3 and basic infiltration rate ranging between 20 cm/hr to 32 cm/hr. the investigation showed that fewer than 50% speed, the application efficiency was 87.2%, the coefficient uniformity 83% and distribution uniformity 74%. The area lost by wheel tracks and service road was estimated as 1.4% of the total irrigated area. Salih (2004) made performance evaluation on the centre pivot and linear irrigation systems for producing alfalfa at Um Dom farm of the Arab company for Agricultural production and processing , Khartoum north. The systems were running at two different speeds, being 75% and 40% for the centre pivot and 90% and 45% for the linear systems the respective values of coefficient uniformity were 71.3% and 44.3% for centre pivot, while for linear system they were

30 72.7% and 70.2 % respectively. These values were considered low as compared to a normal value of 85%. For the distribution uniformity they also gave low values being 56.2% and 60.9% for the centre pivot and 64.3% and 59.2% for the linear system. On the other hand when the centre pivot was compared with traditional method for producing alfalfa and sorghum fodder showed an advantage from an economical view point. Adam (2006) studied the design and development of an automated sprinkler system at Faculty of Agriculture University of Khartoum demonstration farm, he ended up by providing a computer model using Microsoft Visual Basic 6.0 (sp.6), which was verified on a solid set (permanent) system, the evaluation of the automated sprinkler system gave values of distribution uniformity of 81% and 82% and for coefficient uniformity they were 88% and 89%, the application efficiencies were 90% and 78% respectively for one (square) pattern zone and for the whole system.

31 CHAPTER THREE MATERIALS AND METHODS

3.1 Prelude The experimental work was carried out during two seasons 2005/2006, 2006/2007. It consisted of assembling and evaluating the performance of centre pivot irrigation system in new Hamadab irrigation project. Which is one of four resettlement projects associated with the implementation of Merwai Dam. The project area is about 29000 Feddan, it lies on the western side of the River Nile about 20km from El Debba town.-El Debba province - Northern state. It is confined between lat. 17o55′11″ and 17o58′11″N and long 31-06 – 08 and 31 – 13 – 31E. The area of the project lies in a desert climate of an average annual rainfall of 12 mm (occurring mainly in July – August). The mean daily temperature is about 37oC and the mean minimum temperature is 22oC. The mean annual temperature is 29oC. The mean maximum temperature is 29.6oC. Table 3.1 shows climatic data for 30 years (1971 – 2000) as obtained from Karima Meteorological station. The project lies mainly in mordantly suitable land with erosion hazards and fertility limitation. The infiltration rate of the soil is within the range of 17 -18 cm/hr. The irrigation network is as shown in Map 3.1. It consists of a main canal taking water from a pump station situated on the western bank of the River Nile. It has four pumps each designed to deliver 3 5m /s. Four secondary canals (S1, S2, S3, S4) off take from both sides

Table 3.1 Climate data from Karima metrological station (1941-1970)

Temp. for 30 year Jan Feb. March April May June July Aug. Sept. Oct. Nov. Dec. Year Mean maximum 28.8 30.6 34.6 38.4 41.7 43.1 41.4 40.7 41.4 39.0 33.7 29.5 36.9 Mean minimum 12.6 13.6 17.1 21.1 24.7 26.8 26.9 27.3 26.7 24.0 19.0 14.0 21.2 Average annual 20.7 22.1 25.9 29.8 33.3 34.6 34.2 34.0 31.5 31.5 26.3 21.8 29.6 Average rainfall tr tr Tr tr tr tr 13 23 4 4 tr tr 41 (mm) Potential evapotran- 1312.9 1303.4 1887.9 1984.5 3038 2079 1953 11785 1764 1822.8 1562.8 1280.3 121773.2 spiration (mm)

Source: Climatological Normals (1941-1970) Sudan Meteorological Services.

Map 3.1 New Hamadab Agricultural Project

34 of the main canal. S1 and S2 off take before a booster pump station while S3 and S4 off take after a booster pump station, which has equal number of pumps, each delivering 2.4 m3/s. The secondary canals are further subdivided into branches, minors and field canals (Abu XXs and Abu VIs) thereby commanding the whole area which includes farmers tenancies, research and demonstration plots.Five centre pivot irrigation systems are located adjacently on the western side of S4.The study includes assembling of the centre pivot irrigation systems, then evaluating their performances with reference to hydraulic standards and compared to conventional irrigation practices after being planted with wheat and subjected to similar cultural practices except method of irrigation.

3.2 Pivot assembly The assembly is done with the help of an erection crew. The following tools are necessary items to carry out the assembly operation. 1. A boom truck with 15m height and 3 tons lifting capacity (Plate 3.1) 2. A medium size tractor with a loader. 3. A chain or nylon strap (Plate 3.1). 4. An electric impact wrench coupled with electric generator, alternatively a drive air wrench can be used. 5. A set of hand tools (different sizes) 6. GPS (Global Position System).

Plate 3.1 A boom truck and nylon strap

36 The centre pivot usually comes in 40ft container with all different items (Plate 3.2). After locating the exact position of the system with the help of the GPS, a concrete pad (Plate 3.3) is constructed according to specifications given by the manufacturer. The pivot head (Plate 3.4) weldment is fixed to the pivot legs and both are fixed by 4 anchoring bolts to the concrete pad (Fig 3.1). The spans are erected according to the following procedure. a. The pipes are laid and bolted together (Plate 3.5) b. Trust rods and trust angles are laid end – to – end along both sides of the pipe (Plate 3.5) c. Using the boom truck or the tractor with loader the pipes are bolted to truss rods and truss angles, starting from the first pipe followed by the second one and so on until the last pipe in span (Plate 3.5). d. Span cable, U-pipes and associated hardware (Fig 3.2) are installed prior to raising the span (Plate 3.6) e. Tower legs are bolted to the drive tube with motor mounting bracket facing the last tower of the pivot. f. The tower ties are then bolted. g. Other parts including motors, gearboxes, with tires, drive shafts and guard are mounted bolted and tightened (Plate 3.7). Towers are connected to each other starting with the first tower which is connected to the pivot weldment (Plate 3.8) using a rubber hose with clamps, connection is carried out to other spans using the boom truck, the strap (Plate 3.1) and the towing wheel (Plate 3.9) and rubber hoses with clamps (Plate 3.10). Electrical components such as control panel, collector ring (Plate 3.11), tower boxes and centre motors are connected.

Plate 3.2 Centre pivot a complete package

Plate 3.3 Centre pivot concrete pad and trench

Plate 3.4 Centre pivot head fixed to its legs

Fig 3.1 Concrete pad with 4 anchor bolts

Plate 3.5 The pipe are laid and bolted together

Fig 3.2 Drop pipe and sprinkler

Plate 3.6 The pipe of span

Plate 3.7 Complete span

Plate 3.8 Weldment connected to pivot

Towing wheel

Plate 3.9 Towing wheel

Plate 3.10 Rubber hose with clamps

Plate 3.11 Collect or ring

49 Drop pipes and nozzles are connected (Fig 3.2 and Plate 3.7) then the system is aligned and connected to the power and water source (open channel). A centrifugal pump driven by a diesel engine single or double stage (Plates 3.12 and 3.13) is connected to a suction basin (Plate 3.14) at the side of the channel. The pump is connected to the centre pivot system by interconnected PVC pipes (Plate 3.15). The pipe is connected at both ends to the pump and centre pivot system by zee pipes (Plates 3. 16 and 3.17). The centre pivot system is electrically powered from a generator operated by the diesel engine and checked by a voltmeter. The water flow rates and pressures from the pump and at the nozzles are monitored by cumulative flow meters (Plate 3.18) and pressure gauges (Plate 3.19) respectively. A safety device is incorporated in the system to safeguard the system against failures.

3.3 Hydraulic performance Uniformity coefficient, distribution uniformity (pattern efficiency), and Ea of the centre pivot irrigation system were measured using spray cans as described by Evan et al. (1996). The system was made to run at two different speeds (40,100%). Catch cans (44) (Plate 3.20) are placed at equal distances in a straight line from pivot point towards the outward direction. The system was allowed to pass over the cans and graduated measuring cylinder (Plate 3.21) are used to measure the volume of water being caught. A conversion factor based on the area of the can was used to convert the volume in milliliters to depth in millimeters. Wind speed and direction, relative humidity, temperature and time of test were recorded from Karima meteorological station.

Plate 3.12 Diesel engine with single pump

Plate 3.13 Diesel engine with double pump

Plate 3.14 Section basin

Plate 3.15 P.V.C pipes (∅ 9″)

Zee pipe

Plate 3.16 Zee pipe from single stage pump

Zee pipe

Plate 3.17 Zee pipe from double stage pump

56 Flow meter

Fan

Plate 3.18 Flow meter

Pressure gauge

Plate 3.19 Pressure gauge

Plate 3.20 Catch cans

Measuring cylinder

Plate 3.21 Water measurement

3.3.1 Uniformity coefficient (CU)

60 Christiansen’s coefficient of uniformity (CU) expressed as a percentage was determined as expressed by Zoldoske and Solomon (1988) following equation (2.2): D CU = (1− )×100 M 2.2 Where: CU = Christiansen’s coefficient of uniformity (%). D = Average absolute deviation from the mean application rate, (mm). M = Average application rate, (mm).

3.3.2 Distribution uniformity or pattern efficiency (DU) The distribution uniformity is computed by dividing the average low quarter caught in the cans by the average depth caught in all cans. This is expressed by equation (2.3) as suggested by Zoldoske and Salomon (1988): DU = Average low quarter caught in the cans × 100 2.3 Average depth caught in all cans Where: DU = Distribution uniformity (%)

3.3.3 Application efficiency (Ea%) The application efficiency of the centre pivot irrigation systems was calculated using the average depth of application as monitored by the system flow meter (Wf) and the average depth of water caught in the spray cans (Ws). Then the application efficiency (Ea%) was calculated using the following formula as suggested by Israelsen et al. (1967): ws Ea % = × 100 2.4 wf

61 wf is calculated using the flowing formula wf = GPM × 3.78 × 6 × T A × 4200 Where: GPM = Amount of water read at flow meter in gallons per mint T = time required to fionit one raud. A = Area in Fadden covered by the system.

3.3.4 Overall Irrigation efficiency The overall irrigation efficiency % = Application efficiency × Distribution uniformity 3 .1

3.3.5Percentage of loss in the cultivable area The area lost as wheel path (or track) (Plate 3.22) was calculated as follows: 1. The length from pivot point to outer edge of the first wheel path was measured using a metering tape, then the area of this circle was determined. 2. The length from pivot point to the inner edge of the first wheel path was measured and the area of this circle was determined. 3. The area lost by the first wheel path is calculated as the difference between the result of step (1) and (2). 4. This procedure is repeated for the other eight wheel paths. 5. The total area lost by wheels path is added to the area lost to the road. Then the loss in area is presented as a percentage of the total irrigated area.

Gravels

Plate 3.22 Wheel track

63 3.4 Irrigation water measurements The water delivered by the pump was measured by a cumulative flow meter. At each secondary canal offtake measurements were done by well head regulator by the following relation, which was commonly used by the civil engineering.

Q = CA H 3.2 Where: Q = discharge (m3/s) C = constant = 3 A = pipe c.s area (m2) H = effective head (m) difference between u/s and d/s water levels. Surveying equipments (engineer’s level and staff rod) were used to determine (H) while a measuring tape was used to measure pipe internal diameter. The procedure was also used for Abu XXs field outlet pipes (FOP) at the field level. The total amount of water applied to the crop was estimated by the relation:- Average FOP flow rate × operating hrs × total number of irrigations. Then when divided by total area will give m3/feddan/season

3.5 Measurement at centre pivot system The amount of water pumped into a centre pivot system was measured by the flow meter (gallon/min), (Plate 3.18) which was converted into (m3/s) then multiplied by the operating time (hrs/day) and again multiplied by total number of irrigations.

64 Then when divided by total area will give m3/feddan/season.

3.6 Plant parameters The tools used to measure plant parameters included a ruler, a vernier and a weighing balance.

3.6.1 Plant height (cm) This was measured from plant emergence up to maturity stage using a ruler.

3.6.2 Crop density A one meter square grid was thrown at random and plants inside the square were counted to give number of plants/m2.

3.6.3 Number of tillers Number of tillers/plants was recorded.

3.6.4 Spike length The length of the spike was measured using a ruler.

3.6.5 Number of seeds/spike The number of seeds per each spike was counted and recorded.

3.6.6 Weight of 1000 grain Using an electronic weighing balance, 1000 seeds were cleaned and weighed.

3.6.7 Stem thickness Average stem thickness was measured using a vernier scale.

CHAPTER FOUR RESULTS AND DISCUSSION

4.1 Technical performance Application efficiency, (Ea %), uniformity coefficient (CU) and distribution efficiency (pattern efficiency), (DU) were the main variables considered for evaluating the performance of the centre pivot irrigation system under investigation. On the other hand the plant growth attributes and yield with its components were also considered in evaluating the system as compared to the conventional surface irrigation method. These parameters include plant height, leaf area index, number of leaves per plant, stem size, plant density, number of seeds per plant, 1000 grain weight and yield. Uniformity coefficient and distribution uniformity were the variables used for performance evaluation of centre pivot, whereas ,plant density, leaf area index, number of leaves, stem size, plant height, number of seeds per plant, weight of 1000 grain and yield were the variables used for comparing centre pivot irrigation systems with surface irrigation system.

4.2.1 Uniformity coefficient The uniformity coefficient for centre pivot irrigation system under investigation was determined using equation (2.1) as suggested by Zoldoske et al. (1988) and the data is given in the tabular form of appendix for centre pivot running at 40% and 100% speed respectively. Appendix (B) shows sample calculation of CU for the centre pivot irrigation system using equation (2.1) D CU = (1 − ) × 100 2.1 M Where:

66 CU = Christiansen’s coefficient of uniformity (%). D = Average absolute deviation from the mean application rate, (mm). M = Average application rate, (mm). a) CU for the centre pivot system are: i- Running at 40% = 75% ii- Running at 100% = 85% The CU value at 40% was lower than the 85% of value normally recommended for sprinkler systems (Michael, 1978). This low value of uniformity coefficient obtained under centre pivot can be attributed to clogging of nozzles in system, which were improperly calibrate.

4.2.2 Uniformity distribution (DU) This is determined using equation (2.2) and the data is given in the tabular form of Table 4.1 and 4.2 for centre pivot running at 40% and 100%. Respectively Appendix (C) show sample calculation of DU for the centre pivot irrigation using the following equation (2.3): DU = Average low quarter caught in the cans × 100 2.3 Average depth caught in all cans Where: DU = Distribution uniformity (%) a) DU for the centre pivot system: i- Running at 40% = 60% ii- Running at 100% = 76%

These DU values for the centre pivot irrigation system are considered low at 40% and high at 100% as compared to standard

67 values under ideal conditions, because under 100% speed the system move continuously where as under 40% the system stops 60% of running time and move only 40% which may result less uniform distribution.

4.2.3 Application efficiency (Ea%) This is determined using equation 3.3 and the data is given in the tabular form of Appendix (C) for the centre pivot running at 40% and 100%. ws Ea % = × 100 2.4 wf Where: WS = depth of water caught in the spray cans in (mm) wf = average depth of application as monitored by system flow meter in (mm). Ea = application efficiency %. Ea =for the centre pivot running at 40% = 53% Ea = for the centre pivot running at 100% = 47%.

These values of Ea are low compared to the result obtained by Osman 2004 at Ras Alwadi. This maybe due to the change in charting of nozzles as two towers of the system were dismantled and removed (the area of the centre pivot educed from 180 fed to 110 fed).

4.3 Plant parameters 4.3.1 Plant density, number of leaves, leaf area index, stem size and plant height

68 Tables 4.1, 4.2, 4.3, 4.4 and 4.5, Appendix (F) and Plates 4.1, 4.2 and 4.3 show that centre pivot result is greater plant density( number of plants/m2), number of leaves per plant, leaf area index, stem size(mm) and plant height (cm) significantly as compared to surface irrigation in pilot and tenant farms. The latter is considered control. This result may be attributed mainly to the highly uniform distribution of water by the centre pivot system. Also the precision sowing by the seed drill as compared to manual broadcasting used in the pilot and tenant farms. This result agrees with the findings of Saeed (2001), Salih (2004) and USDA (2005), who stated that plant growth and plant density increased under centre pivot compared to surface irrigation system. On the other hand the pilot farm has significant increase over tenant’s farm with respect to plant density(plant/m2), (Table 4.1), number of leaves per plant (Table 4.2), leaf area index (Table 4.3); but there are no significant differences in so far as the stem size and plant height are concerned (Tables 4.4 and 4.5), respectively.

69 Table 4.1 Plant density (number of plants/m2)

B1 B2 B3 B4 mean

Tenant farm 241 256 302 280 269.75b Centre pivot 540 492 620 465 529.25 a Pilot farm 120 129 120 115 121c