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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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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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