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UNIVERSITI PUTRA MALAYSIA MOHAMMED ISA BAMMAMI FK 2015 40 IMPACTS OF SOIL COMPACTION ON EMITTER PERFORMANCE IN SUB-SURFACE DRIP IRRIGATION SYSTEM

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Page 1: UNIVERSITI PUTRA MALAYSIApsasir.upm.edu.my/56673/1/FK 2015 40RR.pdf · universiti putra malaysia mohammed isa bammami fk 2015 40 impacts of soil compaction on emitter performance

UNIVERSITI PUTRA MALAYSIA

MOHAMMED ISA BAMMAMI

FK 2015 40

IMPACTS OF SOIL COMPACTION ON EMITTER PERFORMANCE IN SUB-SURFACE DRIP IRRIGATION SYSTEM

Page 2: UNIVERSITI PUTRA MALAYSIApsasir.upm.edu.my/56673/1/FK 2015 40RR.pdf · universiti putra malaysia mohammed isa bammami fk 2015 40 impacts of soil compaction on emitter performance

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IMPACTS OF SOIL COMPACTION ON EMITTER PERFORMANCE IN SUB-

SURFACE DRIP IRRIGATION SYSTEM

By

MOHAMMED ISA BAMMAMI

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in

Fulfillment of the Requirements for the Degree of Master of Science

May 2015

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COPYRIGHT

All materials obtained within the thesis, including without limitation text, logos, icons,

photographs and all other artwork, is copyright material of Universiti Putra Malaysia

unless otherwise stated. Use may be made of any material contained within the thesis

for non-commercial purposes from the copyright holder. Commercial use of material

may only be made with the express, prior written permission of Universiti Putra

Malaysia.

Copyright Universiti Putra Malaysia

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DEDICATION

This thesis is dedicated to the Almighty Allah who has been my helper, sustainer,

provider, guide, source of encouragement, keeper and my all in all throughout the

course of my studies and also to my parents (Alhaji Isa Mohammed and Hajiya Fatima

Mohammed) whose prayers and support has kept me going. Finally to my brothers

Mohammed Isa, Adamu Mohammed and Sadiq Mohammed, my sisters Fatima and

Maryam who are always by my side and ready with any kind of assistance.

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Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfillment of

the requirement for the degree of Master of Science

IMPACTS OF SOIL COMPACTION ON EMITTER PERFORMANCE IN SUB-

SURFACE DRIP IRRIGATION SYSTEM

By

MOHAMMED ISA BAMMAMI

May 2015

Chairman: Md Rowshon Kamal, PhD

Faculty: Engineering

This research focuses the effect of soil compaction on performance of the Subsurface

Drip Irrigation (SDI) system; since the emitters in this system are buried, by operating

heavy farm machineries on the field, compaction is bound to occur and secondly

finding methods of improving emitter performance, mainly in circumstances where the

soil is compacted. Subsurface drip irrigation provides the required amount of water and

fertilizer, directly onto the plant root zone with a high efficiency. However, SDI

performance is often affected by poor distribution uniformity of emitters. Therefore,

the aim of this study is to investigate the variation of the emitters’ discharge rate and

wetting patterns on SDI system performance due to soil compaction. To achieve this

objective an experiment consisting of an air tank, water reservoir, digital flow meter,

digital penetrologger, pressure gauge, emitters with three discharge rates of 2, 4, and 8

L/hr, three different soil samples loosely packed in lysimeters were carried out.

Emitters were buried at a depth of 10 cm, 20 cm, and 30 cm in the lysimeters. External

load was applied onto the soil surface while monitoring the discharge rate of emitters

using the digital flow meter. The soil cone index was determined at different soil depth

using the digital penetrologger. Data collected from these two devices were then used

to establish a relationship between soil cone index and emitter discharge coefficient.

Using the relationship developed, by imputing cone index (MPa) into the equation; the

decrease in emitter discharge rate q can be predicted. A significant negative correlation

was found between the cone index and emitter discharge rate. For all experiments using

three soil samples, a substantial decrease in emitter discharge and emitter wetting

diameter was observed. A decrease of 60% to 100% in the emitter discharge rate

depending on the soil exposure to loading was recorded and 15% to 50% decrease in

wetting diameter were recorded depending on the soil type and decrease in emitter

discharge rate. Data obtained from the experiment was further fed into the HYDRUS

software to simulate the wetting pattern of the emitters before and after compaction. A

significant decrease in emitter discharge rate with the increase in a soil cone index was

observed and consequently, a decrease in emitter wetting diameter. This study has

shown a greater effect of compaction on emitter discharge rate compared to emitter

wetting diameter. To ameliorate the effect of compaction on the emitter performance,

the emitter operating pressure was increased from 1 bar to 1.5 bars; even at higher soil

cone index, emitter discharge rate increases with the increase of operating pressure.

Emitters buried at deeper lateral depth, have shown a higher resistance to soil

compaction. In conclusion, this study has shown that emitter discharge rate and wetting

diameter decreases with the increase in soil cone index and encourages deeper lateral

depth and higher operating pressure depending on a soil cone index.

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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai

memenuhi keperluan untuk ijazah Master Sains

KESAN PEMADATAN TANAH KE ATAS PRESTASI PEMANCAR PADA

SISTEM PENGAIRAN TITIS BAWAH PERMUKAAN

Oleh

MOHAMMED ISA BAMMAMI

May 2015

Pengerusi: Md Rowshon Kamal, PhD

Fakulti: Kejuruteraan

Kajian ini memberi tumpuan terhadap kesan pemadatan tanah ke atas prestasi sistem pengairan

titis bawah permukaan (SDI); sejak pemancar dalam sistem ini ditanam, dengan mengendalikan

jentera berat di ladang, pemadatan tanah pasti akan berlaku dan kedua mencari kaedah untuk

meningkatkan prestasi pemancar, terutamanya dalam keadaan tanah yang dipadatkan. Pengairan

titis bawah permukaan menyediakan jumlah air dan baja yang diperlukan terus ke zon akar

tumbuhan dengan kecekapan yang tinggi. Walau bagaimanapun, prestasi SDI sering dipengaruhi

oleh keseragaman pengagihan pemancar yang rendah. Oleh itu, tujuan kajian ini adalah untuk

menyiasat perubahan kadar pelepasan pemancar dan corak kebasahan pada prestasi sistem SDI

disebabkan oleh kepadatan tanah. Untuk mencapai matlamat ini satu eksperimen yang terdiri

daripada tangki udara, takungan air, meter aliran digital, penetrologger digital, tolok tekanan,

pemancar dengan tiga kadar pelepasan 2, 4, dan 8 L/jam dan tiga sampel tanah pada kelonggaran

berbeza dibungkus menggunakan lysimeter telah ditanam di bawah permukaan tanah pada

kedalaman 10, 20, dan 30 cm. Beban luaran telah dikenakan ke atas permukaan tanah sambil

kadar pelepasan daripada pemancar dipantau menggunakan meter aliran digital. Indeks kon tanah

ditentukan pada kedalaman tanah yang berbeza menggunakan penetrologger digital. Data yang

dikumpul daripada kedua-dua peranti kemudiannya digunakan untuk membina hubungan antara

indeks kon tanah dan pekali kadar alir pemancar. Menggunakan hubungan yang dibangunkan

dengan memasukkan indeks kon tanah (MPa) ke dalam persamaan; penurunan dalam kadar

pelepasan pemancar, q dapat diramalkan. Korelasi negatif yang signifikan didapati wujud antara

indeks kon tanah dan pemancar kadar pelepasan, q. Dalam semua ujikaji yang dijalankan ke atas

ketiga-tiga sampel tanah, penurunan yang ketara dalam pelapasan pemancar dan garis pusat

pembasahan pemancar diperhatikan. Pengurangan sebanyak 60% hingga 100% dalam kadar

pelepasan pemancar bergantung kepada pendedahan tanah kepada bebanan telah dicatatkan dan

15% hingga 50% pengurangan dalam diameter kebasahan telah dicatatkan bergantung kepada

jenis tanah dan penurunan kadar pelepasan pemancar. Data yang diperolehi daripada eksperimen

terus dimasukkan ke dalam perisian Hydrus untuk menyimulasikan corak kebasahan bagi

pemancar sebelum dan selepas pemadatan tanah. Penurunan ketara dalam kadar pelepasan

pemancar dengan peningkatan dalam indeks kon tanah diperhatikan dan akibatnya, diameter

kebasahan pemancar tealh menurun. Kajian ini telah menunjukkan kesan pemadatan tanah adalah

lebih besar terhadap kadar pelepasan pemancar berbanding garis pusat pembasahan. Untuk

memperbaiki kesan pemadatan prestasi pemancar, tekanan pemancar telah ditingkatkan daripada

1 bar kepada 1.5 bar; walaupun pada indeks kon tanah yang lebih tinggi, kadar pelepasan

pemancar meningkat dengan peningkatan tekanan operasi. Pemancar ditanam pada kedalaman

yang lebih mendalam secara sisi, telah menunjukkan ketahanan yang lebih tinggi terhadap

pemadatan tanah. Kesimpulannya, kajian ini telah menunjukkan bahawa kadar pelepasan

pemancar dan diameter kebasahan berkurangan dengan peningkatan indeks kon tanah dan

menggalakkan kedalaman sisi yang lebih mendalam dan tekanan operasi yang lebih tinggi

bergantung kepada indeks kon tanah.

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AKNOWLEDGEMENTS

Immense adoration, glorification, supplication and gratitude are due to ALMIGHTY

ALLAH for the gift of life, health, vision and endless mercies upon me. No doubt, Dr

Md Rowshon Kamal (Chairman), Dr. Aimrun Wayayok and Mr Mohamed Azwan b.

Mohamed Zawawi and Mr Hafiz are indeed a perfect team and a delight to every

student. Numerous thanks to Prof Ir Dr Mohd Amin Mohd Soom and Dr Rowshon for

their great support and assistance throughout the work, for providing guidance and

inspiring drill in soil and water analysis. To the following friends for the quality time

spent Elhayat, Radatech, Leko, Emeka Okoli Jude, Abba Babakura, Abdul Gwadowali,

Versace Golden, Abdussamad, Aminu Dogo, Abiso, Talha Ibrahim and numerous other

internationals and Nigerian friends too many to inscribe. My profound gratitude goes

to my parents, Alh. Mohammed isa, and Haj. Fatima mohammed, for their endless

supports towards the successful completion of my master’s program. I also deem it

necessary to express my sincere appreciation to my brothers, Dr. Mohammed Isa, Dr.

Adamu Mohammed and Engr. Sadiq Bammami and my sisters Fatima and Maryam

Bammami for their encouragement and patience, who are always by my side and ready

with any kind of assistance. Esteem appreciation to my siblings, nieces, nephews, aunts

and cousins.

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APPROVAL

I certify that a Thesis Examination Committee has met on 03 April 2015 to conduct the

final examination of Mohammed Isa Bammami on his Master of Science Thesis

entitled “IMPACT OF SOIL COMPACTION ON EMITTER PERFORMANCE IN

SUB-SURFACE DRIP IRRIGATION SYSTEM” In Accordance with the Universities

and University College Act1971 and the constitution of the Universiti Putra Malaysia

[P.U.(A) 106] 15 March 1998. The Committee recommends that the student be

awarded the Master of Science degree.

Members of the Examinations Committee were as follows:

______________________PhD

Lecturer

Faculty of ………………

Universiti Putra Malaysia

(Chairman)

………………………….., PhD

Lecturer

Faculty of ……………….

Universiti Putra Malaysia

(Internal Examiner)

………………………….., PhD

Lecturer

Faculty of …………………

Universiti Putra Malaysia

(Internal Examiner)

………………………….., PhD

Lecturer

……………………………

(External Examiner)

_______________________

ZULKARNAIN ZAINAL, PhD

Professor and Deputy Dean

School of Graduate Studies

Universiti Putra Malaysia

Date: 13 May 2015

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This thesis was submitted to the Senate of Universiti Putra Malaysia and has been

accepted as fulfillment of the requirements for the degree of Master of Science. The

members of the Supervisory Committee were as follows:

Md Rowshon Kamal, PhD

Senior Lecturer

Faculty of Engineering,

Universiti Putra Malaysia

(Chairman)

Aimrun Wayayok, PhD Senior Lecturer

Faculty of Engineering,

Universiti Putra Malaysia

(Member)

Mohamed Azwan b. Mohamed Zawawi Senior Lecturer,

Faculty of Engineering,

Universiti Putra Malaysia

(Member)

_______________________

BUJANG KIM HUAT, PhD

Professor and Dean

School of Graduate Studies

Universiti Putra Malaysia

Date

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Declaration by graduate student

I hereby confirm that: this thesis is my original work;

quotations, illustrations and citations have been duly referenced;

this thesis has not been submitted previously or concurrently for any other degree at

any other institutions;

intellectual property from the thesis and copyright of thesis are fully-owned by

Universiti Putra Malaysia, as according to the Universiti Putra Malaysia (Research)

Rules 2012;

written permission must be obtained from supervisor and the office of Deputy Vice-

Chancellor (Research and Innovation) before thesis is published (in the form of

written, printed or in electronic form) including books, journals, modules,

proceedings, popular writings, seminar papers, manuscripts, posters, reports, lecture

notes, learning modules or any other materials as stated in the Universiti Putra

Malaysia (Research) Rules 2012;

there is no plagiarism or data falsification/fabrication in the thesis, and scholarly

integrity is upheld as according to the Universiti Putra Malaysia (Graduate Studies)

Rules 2003 (Revision 2012-2013) and the Universiti Putra Malaysia (Research)

Rules 2012. The thesis has undergone plagiarism detection software.

Signature: ________________________ Date: 13th

May, 2015

Name and Matric No: Mohammed Isa Bammami and GS36536

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Declaration by Members of Supervisory Committee

This is to confirm that:

the research conducted and the writing of this thesis was under our supervision,

Supervision responsibilities as stated in Rule 41 in Rules 2003 (Revision 2012-

2013) were adhered to.

Signature _____________________________

Name of Chairman of Supervisory Committee

Md Rowshon Kamal, PhD

Signature ____________________________

Name of Member of Supervisory Committee

Aimrun Wayayok, PhD

Signature ____________________________

Name of Member of Supervisory Committee

Mohd Amin Mohd Soom, PhD

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1. TABLE OF CONTENTS

Page

ABSTRACT i

ABSTRAK ii

ACKNOWLEDGEMENTS iii

APPROVAL iv

DECLARATION vi

LIST OF TABLES iix

LIST OF FIGURES x

CHAPTER

1 INTRODUCTION 1 1.1 Background of the Study 1

1.2 Problem Statement 2

1.3 Research Objectives 3 1.4 Importance of the Study 3 1.5 Organization of Thesis 3

2 LITERATURE REVIEW 3 2.1 Introduction 3

2.2 Intensity of Compaction in Soil Profile 3 2.3 SDI Lateral Placements 4

2.4 Laterals within Soil Exposed to Compaction 4 2.5 SDI and Soil Hydraulic Properties 5 2.6 Emitter Wetting Pattern 8

2.7 Factors Influencing Emitter Wetting Pattern 9 2.8 Comparisons between Models Predicting Emitter Wetting Pattern 10 2.8 HYDRUS Application 13

3 METHODOLOGY 13 3.0 Introduction 13

3.2 Research Design 13

3.1 Experimental Setup 13

3.2 Wetting Pattern 14

4 RESULTS AND DISCUSSION 17 4.1 Relationship between Emitter Discharge and CI 17

4.2 Relationship between Emitter Discharge Coefficient and CI 43

4.3 Response of Emitter Wetting Pattern to Change in Soil CI 52

5 SUMMARY, CONCLUSION AND RECOMMENDATION 83

5.1 Summary 83

5.2 Recommendations 85 REFERENCES 86

APPENDIX 88

BIODATA OF STUDENT 114

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LIST OF TABLES

Table Page

4. 1 Measured soil properties from particle size analysis. 17

4.2 Observed discharge rates under different compaction rates, soil depth and

operating pressures for the loamy sand soil sample for all sdi emitters. 18

4.3 Correlation between discharge rate of 8 l/hr and cone index in loamy sand 18

4.4 Ccorrelation between discharge rate of 4 l/hr and cone index in loamy sand 21

4.5 Correlation between discharge rate of 2 l/hr and cone index in loamy sand 23

4.6 Observed discharge rates under different compaction rates, soil depth and

operating pressures for the sandy clay loam soil sample 26

4.7 Correlation between discharge rate of 8 l/hr and cone index in sand clay loam 27

4.8 Correlation between discharge rate of 4 l/hr and cone index in sandy clay loam 29

4.9 Correlation between discharge rate of 2 l/hr and cone index in sandy clay loam 32

4.10 Observed emitter discharge rates under different compaction rates, soil depth and

operating pressures for the sandy clay soil sample 35

4.11 Correlations between discharge rate of 8 l/hr and soil cone index 36

4.12 Correlation between4 l/hr emitter buried in sandy clay and cone index 38

4.13 Correlations between discharge rate of 2 l/hr and soil cone index 40

4.14 Average coefficient of discharge (k) of 8 l/hr emitter at 1, 1.25 and 1.5 bar. 43

4.15 Average coefficient of discharge (k ) of 4 l/hr emitter at 1, 1.25 and 1.5 bar. 45

4.16 Average coefficient of discharge (k) of 2 l/hr emitter at 1, 1.25 and 1.5 bar. 47

4.17 Summary of wetting pattern differences between the buried emitter’s best

performance wetting pattern at initial soil cone index and worst emitter

performance wetting at the final cone index recorded in loamy sand. 62

4.18 Summary of wetting pattern differences between the buried emitter’s best

performance wetting pattern at initial soil cone index and worst emitter

performance wetting at the final cone index recorded in sandy clay loam. 72

4.19 Summary of wetting pattern differences between the buried emitter’s best

performance wetting pattern at initial soil cone index and worst emitter

performance wetting at the final cone index recorded in sandy clay. 82

4.20 General equations for determining coefficient of emitter discharge rate at a given

cone index (mpa). 84

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LIST OF FIGURES

Figure Page

4. 1 Decrease of discharge rate with increasing compaction C.I (MPa) in loamy

sand for 8 L/hr emitter. 19

4.2 Reduction of discharge rate from 8 L/hr emitter operating at 1, 1.25, and 1.5

bar with increase in C.I (MPa). 19

4.3 8 L/hr emitter discharge rates versus emitter lateral depth. 20

4.5 Reduction of discharge from 4 L/hr emitter operating at 1 bar in loamy sand

with increase in compaction C.I (MPa) 22

4.6 Reduction of 4 L/hr emitter operating at 1, 1.25, and 1.5 bar with increase in

compaction C.I (MPa) 23

4.7 Variation of nominal emitter discharge rates with 4 L/hr with emitter lateral

depth. 24

4.8 Reduction of discharge from 2 L/hr emitter operating at 1 bar in loamy sand

with increase in soil compaction C.I in MPa 25

4.9 Reduction of discharge of 2 L/hr emitter operating at 1, 1.25, and 1.5 bar in

loamy sand with increase in compaction C.I (MPa). 25

4.10 Variation of nominal emitter discharge rate of 2 L/hr buried in loamy sand

with emitter lateral depth (cm). 27

4.11 Reduction of discharge from 8 L/hr emitter at 1 bar in sandy clay loam with

increase in soil compaction C.I (MPa). 28

4.12 Decrease in discharge of 8 L/hr emitter operating at 1, 1.25, and 1.5 bar in

sandy clay loam with increase in soil compaction C.I (MPa). 29

4.13 Variation in nominal discharge of 8 L/hr emitter buried in sandy clay loam

with emitter lateral depth 30

4.14 Decrease in discharge for 4 L/hr emitter operating at 1 bar in sandy clay

loam with increase in soil compaction C.I (MPa). 31

4.15 Decrease in discharge of 4 L/hr emitter operating at 1, 1.25, and 1.5 bar in

sandy clay loam with increase in soil compaction C.I (MPa). 32

4.16 Variation in nominal discharge rate of 4L/hr emitter buried in sandy clay

loam 33

4.17 Decrease in discharge of 2 L/hr emitter at 1 bar in sandy clay loam with

increase in soil compaction C.I (MPa). 34

4.18 Decrease in discharge of 2 L/hr emitter operating at 1, 1.25, and 1.5 bar in

sandy clay loam with increase in soil compaction C.I (MPa). 34

4.19 Emitter buried in sandy clay loam with discharge rate of 2 L/hr with

increase in emitter lateral depth. 36

4.20 Reduction of discharge rate from 8 L/hr emitter operating at 1 bar in sandy

clay with increase in soil compaction C.I (MPa) 37

4.21 Reduction of discharge rate from 8 L/hr emitter operating at 1, 1.25, and

1.5 bar in sandy clay with increase in soil compaction C.I (MPa). 37

4.22 Variation in nominal emitter discharge with 8 L/hr buried in sandy clay

with emitter lateral depth (cm). 39

4.23 Reduction of discharge rate from 4L/hr emitter operating at 1 bar in sandy

clay with increase in soil compaction C.I (MPa). 39

4.24 Reduction of discharge rate from 4 L/hr emitter operating at 1, 1.25, and

1.5 bar in sandy clay with increase in soil compaction C.I (MPa). 40

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4.25 Variation of nominal emitter discharge of 4 L/hr buried in sandy clay

versus emitter lateral depth (cm) 41

4.26 Reduction of discharge rate from 2 L/hr emitter operating at 1 bar in sandy

clay with increase in soil compaction C.I (MPa). 42

4.27 Reduction of discharge rate from 4 L/hr emitter operating at 1, 1.25, and

1.5 bar in sandy clay with increase in soil compaction C.I (MPa). 42

4.28 Variation of nominal emitter discharge rate of 2 L/hr emitter buried in

sandy clay with emitter lateral depth (cm). 44

4.29 Plot of discharge coefficient (k) against C.I (MPa) for 8 L/hr at 1 bar. 44

4.30 Plot of discharge coefficient (k) against C.I (MPa) for 8 L/hr at 1.25 bar. 45

4.31 Plot of discharge coefficient (k) against C.I (MPa) for 8 L/hr at 1.5 bar. 46

4.32 Plot of discharge coefficient (k) against C.I (MPa) for 4 L/hr at 1 bar. 46

4.33 Plot of discharge coefficient (k) against C.I (MPa) for 4 L/hr at 1.25 bar. 47

4.34 Plot of discharge coefficient (k) against C.I (MPa) for 4 L/hr at 1.5 bar. 48

4.35 Plot of discharge coefficient (k) against C.I (MPa) for 2 L/hr at 1 bar. 49

4.36 Plot of discharge coefficient (k) against C.I (MPa) for 2 L/hr at 1.25 bar. 50

4.37 Plot of discharge coefficient (k) against C.I (MPa) for 2 L/hr at 1.5 bar. 51

4.38 Operational strategies to maintain designed discharge rate with increase in

compaction. 53

4.39 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 10 cm

depth in loamy sand soil 54

4.40 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 10 cm

depth in loamy sand soil. 55

4.41 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 20 cm

depth in loamy sand soil 56

4.42 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 30 cm

depth in loamy sand soil 57

4.43 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 30 cm

depth in loamy sand soil 58

4.44 Wetting patterns for buried emitter with discharge of 4 L/hr buried at 10 cm

depth in loamy sand soil 59

4.45 Wetting patterns for buried emitter with discharge of 4 L/hr buried at 20 cm

depth in loamy sand soil 60

4.46 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 10 cm

depth in loamy sand soil 61

4.47 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 20 cm

depth in loamy sand soil 63

4.48 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 30 cm

depth in sandy clay loam soil. 64

4.49 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 10 cm

depth in sandy clay loam soil 65

4.50 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 20 cm

depth in sandy clay loam soil 66

4.51 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 30 cm

depth in sandy clay loam soil 67

4.52 Wetting patterns for buried emitter with discharge of 4 L/hr buried at 10 cm

depth in sandy clay loam soil 68

4.53 Wetting patterns for buried emitter with discharge of 4 L/hr buried at 20 cm

depth in sandy clay loam soil 69

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4.54 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 10 cm

depth in sandy clay loam soil 70

4.55 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 20 cm

depth in sandy clay loam soil 71

4.56 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 30 cm

depth in sandy clay loam soil 73

4.57 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 10 cm

depth in sandy clay soil 74

4.58 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 20 cm

depth in sandy clay soil 75

4.59 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 30 cm

depth in sandy clay soil 76

4.60 Wetting patterns for buried emitter with discharge of 4 L/hr buried at 10 cm

depth in sandy clay soil 77

4.61 Wetting patterns for buried emitter with discharge of 4 L/hr buried at 20 cm

depth in sandy clay soil 78

4.62 Wetting patterns for buried emitter with discharge of 4 L/hr buried at 30 cm

depth in sandy clay soil 79

4.63 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 10 cm

depth in sandy clay soil 80

4.64 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 20 cm

depth in sandy clay soil. 81

4.65 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 30 cm

depth in sandy clay soil 88

4.66 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 10 cm

depth in loamy sand soil. 89

4.67 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 20 cm

depth in loamy sand soil 90

4.68 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 30 cm

depth in loamy sand soil 91

4.69 Wetting patterns for buried emitter with discharge of 4 L/hr buried at 10 cm

depth in loamy sand soil. 92

4.70 Wetting patterns for buried emitter with discharge of 4 L/hr buried at 20 cm

depth in loamy sand soil 93

4.71 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 10 cm

depth in loamy sand soil 94

4.72 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 20 cm

depth in loamy sand soil 95

4.73 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 30 cm

depth in loamy sand soil. 96

4.74 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 10 cm

depth in sandy clay loam soil 97

4.75 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 20 cm

depth in sandy clay loam soil 98

4.76 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 30 cm

depth in sandy clay loam soil 99

4.77 Wetting patterns for buried emitter with discharge of 4 L/hr buried at 10 cm

depth in sandy clay loam soil 100

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4.78 Wetting patterns for buried emitter with discharge of 4 L/hr buried at 20 cm

depth in sandy clay loam soil 101

4.79 Wetting patterns for buried emitter with discharge of 4 L/hr buried at 30 cm

depth in sandy clay loam soil 102

4.80 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 10 cm

depth in sandy clay loam soil 102

4.81 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 20 cm

depth in sandy clay loam soil 104

4.82 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 30 cm

depth in sandy clay loam soil 105

4.83 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 10 cm

depth in sandy clay soil 106

4.84 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 20 cm

depth in sandy clay soil 107

4.85 Wetting patterns for buried emitter with discharge of 8 L/hr buried at 30 cm

depth in sandy clay soil 108

4.86 Wetting patterns for buried emitter with discharge of 4 L/hr buried at 10 cm

depth in sandy clay soil 109

4.87 Wetting patterns for buried emitter with discharge of 4 L/hr buried at 20 cm

depth in sandy clay soil 110

4.88 Wetting patterns for buried emitter with discharge of 4 L/hr buried at 30 cm

depth in sandy clay soil 111

4.89 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 10 cm

depth in sandy clay soil 112

4.90 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 20 cm

depth in sandy clay soil 113

4.91 Wetting patterns for buried emitter with discharge of 2 L/hr buried at 30 cm

depth in sandy clay soil 114

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CHAPTER ONE

INTRODUCTION

1.1 Background of the Study

With the rapid increase in population growth and climate change limiting the

availability of fresh water for domestic and agricultural purposes, finding new methods

of irrigation with higher efficiencies in terms of good water management and achieving

excellent crop yield simultaneously becomes a necessity to provide enough food for

our alarming increasing population growth.

Analysis on the use of available fresh water worldwide has shown that more than 70 %

of this precious commodity is used for agricultural purpose with poor on farm water

usage efficiency. Badr and Abuarab (2011) reported that about 85 % of water used in

Egypt, a country where water is a scarce commodity is used in irrigating agricultural

field, with poor on farm irrigation efficiency not exceeding 50 %. About 83 % of water

used in Nevada is used for irrigation purposes, 45 % of this water is lost due to

inefficiencies in irrigation processes while only 83 % part of the 55 % of water used in

Nevada agricultural fields is used by the plants and the rest lost by evaporation at the

soil surface (Nevada Water Facts, 1992). Drip irrigation has been suggested as the most

efficient method of irrigation with efficiency of more than 90 % whereas sprinklers are

50 % to 70 % efficient (No, 2005). Subsurface Drip Irrigation (SDI) is the underground

application of the required amount of water and nutrient directly to the plant root. A

well designed and managed SDI uniformly wets the root zone of the field maintaining a

dry soil surface.

Subsurface Drip Irrigation as defined by ASAE (American Society of Agricultural

Engineers) as “application of water below the soil surface through emitters, with

discharge rate generally in the same range as drip irrigation”. SDI can also be defined

on the basis of lateral depth placement, for a system to be classified under SDI requires

lateral placement below tillage depth ensuring lateral survival throughout the season

indicating a degree of permanence. In recent, SDI is widely used to irrigate field crops,

vegetables and fruits, since the development of plastic micro-irrigation technology. In

general, the advantages of SDI systems are to improved efficiency of nutrient uptake,

less water loss from the soil surface due to surface evaporation, zero runoff, less weed

germination and growth. Moreover, an SDI system allows the incorporation of fertilizer

in the irrigation water therefore simultaneously irrigating and applying fertilizer to the

plant. Drip irrigation was introduced in 1960s but more attention escalated on the

system in the 1980s. Yield response of over 30 different crops irrigated under SDI have

shown better or equal yield with a higher water use efficiency in comparison to any

other irrigation system including surface irrigation. In addition, SDI water use savings

ranges from 0 to 50 % when compared with traditional irrigation systems (Camp,

1998). Normally in SDI system setup, lateral depths ranges from 0.10 m to 0.70 m with

a spacing ranging from 0.25 m to 5 m.

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In contrast to conventional surface drip irrigation, the performance of SDI is a function

of the soil condition (soil hydraulic properties). The importance of uniformity of

discharge of any kind of irrigation system cannot be over emphasized. The discharge

rate of any irrigation system determines its irrigation scheduling and quantity of water

to be applied (Wu, 1992). Therefore, any error in discharge uniformity of any irrigation

system can lead to over or under irrigation or deprive the plants from required applied

nutrients especially in subsurface drip irrigation where the application process is not

visible to the eye since it is an underground process. Moreover, since we are

considering precision farming where the equal number of product per plant or equal

sizes of farm produce are required for easy handling and processing, achieving

uniformity of discharge becomes very essential.

The discharge of SDI is a function of soil condition and therefore, when embarking on

SDI system, the soil you are dealing with should come first. With detail study to

enhance this efficient method of irrigation, researchers discovered backpressures to be

one of the greatest limitations of SDI. Back pressures are pressures build up around the

emitter in adjacent and opposite direction, preventing the emitter from discharging

water at it’s designed and expected rate. (Gil, Sánchez, Juana, & Asce, 2011) reported

that positive water (back pressures) may develop around the emitter during irrigation

following the principles of flow from a point source. (Warrick & Shani, 1996) also

reported that emitters operating at a low pressure might discharge at lower rates as a

result of back pressures. The extent of decrease in this discharge depends on the soil

condition. When the infiltration rate of the soil is less than the rate at which water is

discharged by the emitter, pressure builds up around the emitter restricting water

movement away from the emitter.

To ensure uniformity of discharge of SDI system, the soil properties must be taken into

consideration. Farm mechanization is a key factor that can change the soil condition

and therefore, influencing the uniformity of discharge of SDI systems. Any change in

soil condition will have a direct effect on buried emitter’s discharge rate. Up till now,

no investigation has been done to assess the effect of farm mechanization on SDI

discharge rate and wetting pattern. However, researchers have worked and showed the

changes caused by farm machineries on different soils.

1.2 Problem Statement

Operation of farm machineries in the field accelerates soil compaction (Sekwakwa and

Dikinya, 2012) and the performance of Subsurface Drip Irrigation (SDI) depends on

soil condition (Diamantopoulos and Elmaloglou, 2012). Then, the heavy use of farm

machineries will alter the soil condition and subsequently the performance of

Subsurface Drip Irrigation (SDI) since SDI performance depends on soil condition. The

hypothesis of this study is therefore, compaction will affect buried emitter’s design

discharge rate and wetting pattern. The investigation of the variation of the emitter’s

discharge rate and wetting patterns on SDI system performance due to soil compaction

is essential for sustaining the desirable systems performance. This study will focus on

the effect on the changes in soil condition due to compaction on the performance of

buried emitters.

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1.3 Research Objectives

The main objective of this study was to investigate and develop the relationship in

determining optimal operating pressure in accordance to the decreasing of discharge of

SDI emitters and poor water distribution pattern due to the gradual soil compaction.

The specific objectives were:

1. To determine the relationship between the change in discharge with increase

in soil compaction and the most appropriate lateral depth that will reduce the

effect of compaction on discharge rate and wetting pattern..

2. To analyze the change in wetting pattern of buried emitters as compaction

increases using HYDRUS 2D.

1.4 Importance of the Study

The Importance of the study is highlighted below:

This study showed the impact of compaction on emitter discharge rates based on

the degree of soil compaction.

This study established the allowable amount of load the soil can resist without

affecting the rate of discharge of emitters and the soil moisture distribution.

The study suggested practices to reduce the effect of soil compaction such as

stop irrigation or cut off emitter discharge for a specified period before exposing

the soil to any machinery operation.

1.5 Organization of Thesis

This thesis presents the study in a top-down approach. It begins with the functional

description of the subject on Drip Irrigation systems and its importance over other

methods, and then elaborates on the shortcomings of the system. Chapter 2 is mainly

written for reviewing the methods used in this research and related applications for its

use. Intensive study was reported on factors that can affect SDI systems in this chapter.

Papers on HYDRUS 2D/3D which uses the Van Ganuchen model in stimulating

wetting pattern of buried sources was also critically reviewed and its use in related

applications are delineated. In Chapter 3, this study’s methodologies are explained in

full detail, the methods used in finding effects of compaction on emitter discharge and

also the emitter wetting pattern were fully reported and elaborately explained. Chapter

4, reports the experimental result of the research problem and analysis of the data

collected from experiments observed. Finally, in Chapter 5, detailed discussion on the

results obtained and conclusion in summary of the thesis, stating the achievements and

also identifying the future research direction of the work.

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