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Deficit Irrigation for Wheat Cultivation Under Limited Water Supply Condition
Md. Hossain Ali
DISSERTATION.COM
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Deficit Irrigation for Wheat Cultivation Under Limited Water Supply Condition
Copyright © 2008 Md. Hossain Ali All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval
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ISBN-10: 1-59942-686-2 ISBN-13: 978-1-59942-686-0
Deficit Irrigation for Wheat Cultivation Under Limited Water Supply Condition
A Dissertation Submitted to the
Bangladesh Agricultural University, Mymensingh
In Partial fulfillment of the Requirements for the Degree of
Doctor of Philosophy
By
Md. Hossain Ali
Department of Irrigation & Water Management
Bangladesh Agricultural University
Mymensingh
March, 2008
5
Declaration
I declare that, except where otherwise stated, this dissertation is entirely my own work and has
not been submitted in any form to any other University for any degree.
Date: 11.03.2008 (Md. Hossain Ali)
7
Acknowledgements
The author would like to avail the opportunity to express his deepest sense of gratitude and
profound respect to his supervisor, Dr. Md. Rafiqul Hoque, Professor, Department of Irrigation
and Water Management, Bangladesh Agricultural University (BAU), Mymensingh, Bangladesh,
for his support, direction, encouragement, valuable suggestions and constructive criticism, during
the course of this study and preparing the manuscript.
The author is greatly indebted to his co-supervisor, Dr. A. A. Hassan, Chief Scientific Officer,
and Head, Agricultural Engineering Division, Bangladesh Institute of Nuclear Agriculture (BI-
NA); and member of the supervisory committee, Dr. M. A. Khair, Professor, Department of Irri-
gation and Water Management, BAU, for their valuable suggestions and critical review while
preparing the manuscript.
Thanks are due to the authority of BINA for grant me the fellowship under ‘Research and Devel-
opment Project, BINA’, funded by the Government of Bangladesh.
Sincere thanks are due to the staff members of Agricultural Engineering Division, Plant Physiol-
ogy Division, and Soil Science Division of BINA, and BINA sub-station, Ishurdi, for their assis-
tance and cooperation in various ways during the work.
The author would like to extend his thanks to all of the following: Mr. R. K. Dutta, Head, Crop
Physiology Division, BINA, for his permission to use the laboratory facility; Dr. M. A. Sattar,
Head, Soil Science Division, BINA, for his permission to use the Pressure Plate Apparatus; Dr.
Md Ali Azam, Principal Scientific Officer, Plant Breeding Division, BINA, for his assistance in
grain moisture content determination; A. K. M. Azad, Senior Scientific Officer (SSO) and for-
mer in-charge, BINA sub-station, Ishurdi and Dr. M. Badaruddin, SSO and present in-charge,
BINA sub-station, Ishurdi, for their co-operation and assistance during the field work; Md. Rafi-
qul Islam, SO, Agronomy Division, BINA, to facilitate in using his Ice Box for carrying plant
samples.
The author wishes to express his special appreciation and thanks to his family members for their
support, understanding, and patient during the work.
The author
9
Biographical Sketch
The author was born on 31st December, 1966 in Jamalpur District, Bangladesh. He is the second
son of Md. Abdur Rahim and Joygun Nesa. He passed his Secondary School Certificate (SSC)
examination securing first division in 1982 from Battala High School, Jamalpur and Higher Sec-
ondary Certificate (HSC) examination securing first division in 1984 from Nandina College, Ja-
malpur, Bangladesh. He completed his B.Sc.Ag.Engg. (Hons) degree (securing first class, 5th po-
sition in merit) from ‘Bangladesh Agricultural University, Mymensingh, Bangladesh’ in 1988.
He also completed his M.Sc.(Agril. Engg.) in Irrigation & Water Management from the same
University in 1995. He did his M. Engg. Sci. degree from ‘The University of Melbourne, Aus-
tralia’, in 1999. He joined at ‘Bangladesh Rural Electrification Board (REB)’ as Assistant Gen-
eral Manager (Member Service) in 1993. Later, he joined at ‘Bangladesh Institute of Nuclear
Agriculture (BINA)’ in 1994, as Scientific Officer. He was promoted as Senior Scientific Officer
in 2001. He has published 47 research papers in different national and international journals, one
text book (Agricultural Meteorology, from Bangla Academy, Dhaka, Bangladesh, ISBN: 984-07-
4586-7), and seven popular articles. He is member/life-member of several national /foreign pro-
fessional societies.
The author is married to Anjumanara Begum and blessed with one daughter, Sanjida Afiate, and
one son, Irfan Sajid.
The author
11
Abstract
Vertical and horizontal expansion of irrigated agriculture to feed the increasing population has
contributed to excessive groundwater withdrawal and affected the availability of water in terms
of both quality and quantity. To sustain agricultural growth, strategic measures should be
adopted to reduce water consumption while minimizing adverse effect on yield. The effect of
deficit irrigation on wheat yield was studied in three consecutive years (2002-03 to 2004-05) in
field and pot at the experimental farm of Bangladesh Institute of Nuclear Agriculture, Ishurdi,
Bangladesh. Ten irrigation treatments were imposed in a randomized complete block (RCB) de-
sign covering full deficit, no deficit at all, single deficit at different stages, and alternate deficits.
Water deficit was created by withholding irrigation at different growth stages. The results indi-
cate that deficit irrigation strategies affected all aspects of plant growth (leaf area index, chloro-
phyll content, root growth, nutrient uptake, plant height) adversely. Yield attributes were affected
by deficit irrigation treatments although they are not statistically significant in all cases. Differ-
ences in yield attributes among the partial deficits (i.e. single stage or alternate stage deficits) and
no deficit treatments were small, but there was a sharp difference between partial or no deficit,
and full deficit treatment. The grain and straw yields were significantly affected by treatments.
Differences in grain and straw yield among the partial- and no-deficit treatments were small, and
statistically insignificant in most cases. The greatest effect on yield was observed with the addi-
tion of first increment of water at CRI stage. Within all treatments, the well-irrigated treatment
produced the highest grain yield. When compared within single-deficit treatments, the grain yield
reduction was in the order to water deficit at phases: CRI> maximum tillering > booting – head-
ing >flowering- soft dough. Within two deficit strategies, the treatment having alternate irriga-
tion at CRI and booting –heading phase produced higher grain yield over the other one; and this
treatment produced statistically similar yield to those of single-deficit and no-deficit treatments.
This strategy showed the highest harvest ratio, indicating higher proportional accumulation of
assimilates to grain. The crop coefficient (kc) under different ET0 methods for early, crop devel-
opment, middle, and late period ranged from 0.54 to 0.96, 0.95 to 1.36, 1.2 to 1.62, and 0.68 to
1.05, respectively. The Penman-Monteith method resulted in relatively higher kc value than those
of other methods. Non-significant differences were observed by pair ‘t’ test between kc values
determined by various ET0 methods. When the values were averaged over years and methods, a
12
kc value of 0.77, 1.17, 1.41, and 0.89 were found for early, crop development, middle and late
period, respectively. The yield response factor (ky) varied with the growth phase and also among
seasons. On average, the ky for early, maximum tillering, booting-heading, and flowering-soft
dough stages was 0.27, 0.21, 0.25, and 0.17, respectively. The sensitivity index (λi, of Jensen
model) for early, vegetative, booting-heading, and flowering-soft dough phases was 0.35, 0.22,
0.31, and 0.14, respectively. A more sensitive growth stage had a higher value of λi, and there-
fore water supply is more important at early and booting-heading phases. Deficit irrigation effec-
tively boosted water productivity. On average, the single irrigation at early stage (T10) in addition
to post-sowing irrigation saved about 68 % water in comparison to well-irrigated plot (T9) with a
yield reduction of 19 %. Between two alternate deficit strategies, treatment having irrigation at
early and booting-heading stages (T7) saved 39 % water coupled with 16% yield reduction com-
pared to well- irrigated plot. Marginal productivity of irrigation water associated with treatment
T10 and T7 was about two folds of the others. Within the single deficit treatments (T3 to T6), rela-
tive water savings were almost similar (27 – 31 %), but had differences in relative yield reduc-
tion (6 - 2 %). The highest relative yield reduction was associated with deficit at CRI, followed
by tillering, and then booting-heading stage. The highest net financial return from both land- and
water-limiting condition was obtained from alternate deficit treatment (treatment T7). From the
evaluation of yield, irrigation amount, irrigation water productivity, relative water savings, rela-
tive yield reduction, and maximum profit under limited water resource condition, it can be con-
cluded that when limited quantities of water is available, preference should be given to irrigate
first at CRI (if one irrigation is available), then at CRI and booting-heading (if two irrigations are
available), and next at CRI, maximum tillering and booting-heading (if three irrigations are
available) stages of growth.
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Table of Contents Declaration .................................................................................................................................5
Acknowledgements ....................................................................................................................7
Biographical Sketch ...................................................................................................................9
Abstract ....................................................................................................................................11
Table of Contents .....................................................................................................................13
List of Figures .................................................................................................................................. 17 List of Tables ...........................................................................................................................18
List of Appendices ...................................................................................................................20
List of Abbreviations ...............................................................................................................21
List of Symbols ........................................................................................................................23
Chapter 1: Introduction 1.1 General concept of irrigation ...........................................................................................25
1.1.1 Irrigation scheduling ...............................................................................................25
1.1.2 Full irrigation ..........................................................................................................26
1.1.3 Deficit irrigation ......................................................................................................26
1.2 Water resources for irrigation in Bangladesh ..................................................................28
1.2.1 Cropping pattern and water requirement ................................................................29
1.2.2 Consequences of excess withdrawal of groundwater in dry (winter) season .................................................................................................30
1.3 Crop diversification .........................................................................................................31
1.4 Deficit irrigation of wheat ................................................................................................31
1.5 Statement of the problem .................................................................................................32
1.6 Aim and objectives of the study .......................................................................................33
1.7 Scope and relevance of the study .....................................................................................33
14
Chapter 2: Literature Review 2.1 Deficit irrigation
A) Related work done in Bangladesh ...............................................................................35
B) Related work done outside Bangladesh .......................................................................40
2.2 Crop coefficient, Kc .........................................................................................................49
2.3 Yield response factor, Ky .................................................................................................54
2.4 Economic evaluation for deficit irrigation .......................................................................57
2.5 Yield function/ model ......................................................................................................59
Chapter 3: Materials and Methods
3.1 Description of experimental site ......................................................................................63
3.2 Wheat variety and irrigation treatment ............................................................................65
3.3 Crop culture .....................................................................................................................66
3.4 Statistical analysis ............................................................................................................71
3.5 Soil moisture monitoring .................................................................................................71
3.6 Plant growth and bio-chemical analysis ..........................................................................72
3.6.1 Leaf area index ........................................................................................................72
3.6.2 Leaf chlorophyll content .........................................................................................72
3.6.3 Reducing sugar........................................................................................................73
3.7 Determination of leaf water potential ..............................................................................73
3.8 Root study ........................................................................................................................74
3.8.1 Root sampling .........................................................................................................74
3.8.2 Root length density .................................................................................................74
3.9 Calculation of evapotranspiration ....................................................................................75
3.10 Crop coefficient (kc) .......................................................................................................77
3.10.1 Estimating reference crop evapotranspiration (ET0) ............................................78
3.10.2 Expression of kc ....................................................................................................81
3.11 Determination of yield response factor (Ky) ..................................................................81
3.12 Water productivity indices .............................................................................................82
3.12.1 Water productivity ................................................................................................82
3.12.2 Productivity of irrigation water .............................................................................82
15
3.12.3 Marginal productivity of irrigation water .............................................................83
3.13 Economic analysis .........................................................................................................83
3.13.1 Partial budget analysis ..........................................................................................83
3.13.2 Full budget analysis ..............................................................................................84
3.14 Study of yield function/model .......................................................................................85
3.14.1 Determination of crop sensitivity factor for Jensen model ...................................85
3.14.2 Comparison of yield reduction using CROPWAT model ...................................86 Chapter 4: Results and Discussion
4.1 Weather condition during the crop growing period .........................................................87
4.2 Irrigation frequency and total irrigation water under different treatments ......................91
4.3 Leaf water potential .........................................................................................................93
4.4 Physiological reactions to imposed water deficit .............................................................94
4.4.1 Leaf area index ........................................................................................................94
4.4.2 Chlorophyll content of leafs....................................................................................96
4.4.3 Reducing sugar........................................................................................................98
4.4.4 Root density and its distribution .............................................................................98
4.5 Soil moisture extraction ...................................................................................................99
4.6 Nutrient uptake...............................................................................................................102
4.7 Growth and yield attributes of field experiment ............................................................103
4.8 Yield attributes and yield of pot experiment ..................................................................106
4.9 Responds of grain and straw yield .................................................................................107
4.10 Harvest ratio and Harvest index ...................................................................................113
4.11 Yield and ET relationship ............................................................................................115
4.12 Protein content of wheat grain .....................................................................................118
4.13 Crop coefficient ...........................................................................................................118
4.13.1 Crop coefficient under well irrigated condition ..................................................118
4.13.2 Crop coefficient under deficit control .................................................................124
4.13.3 Crop coefficient for single-stage deficit .............................................................126
4.14 Yield response factor ...................................................................................................129
4.14.1 For individual growth period ..............................................................................129
16
4.14.2 For whole growing period ...................................................................................132
4.15 Evaluation of yield model / function for deficit irrigation ...........................................134
4.15.1 Sensitivity index of Jensen model.......................................................................134
4.15.2 Evaluation of other forms of equation ................................................................135
4.16 Water productivity and productivity of irrigation water ..............................................137
4.17 Marginal productivity of irrigation water and relative water saving ...........................142
4.18 Economic evaluation ....................................................................................................142
4.18.1 Economic evaluation under land-limiting condition ...........................................142
4.18.2 Economic evaluation under water-limiting condition .........................................145
Chapter 5: Summary, Conclusion, and Recommendation 5.1 Summary ........................................................................................................................151
5.2 Conclusion .....................................................................................................................155
5.3 Recommendation for future research .............................................................................157
References ..............................................................................................................................159
Appendices .............................................................................................................................181
17
List of Figures 3.1 Location map of the experimental site .............................................................................64
3.2 (a) Partial view of (i) Field plots, and (ii) pot experiment during 2004-05 .....................69
3.2 (b) View of the individual treatment plots at dough stage during 2004-05 .....................70
3.3 Schematic view of the root sampling area .......................................................................75
4.1 Features of climatic elements during the growing seasons ..............................................88
4.2 Rainfall amount during the crop growing period .............................................................90
4.3 Pattern of (a) extra-terrestrial radiation, and (b) ET0 (P-M method)
throughout the growing periods ......................................................................................92
4.4 Yield and ET, and yield and irrigation water relationship .............................................117
4.5 Crop coefficient of well watered treatment as a function of DFS under
different ET0 methods ....................................................................................................122
4.6 Crop coefficient of well watered treatment as a function of growing-
degree-days (GDD) under different ET0 methods .........................................................123
4.7 Crop coefficient for well watered treatment as a function growth stage .......................124
4.8 Crop coefficients for deficit control as a function of DFS under
different ET0 methods ....................................................................................................127
4.9 Relative yield decrease versus relative ET deficit for individual growth stages ...........130
4.10 Relative yield decrease versus relative ET deficit for whole growth period .................... 133
4.11 Pattern and mathematical relation between (a) ET vs. WP, and
(b) IR vs WP, IWP ......................................................................................................141
4.12 (a) Yield vs applied water, (b) Cost and revenue function under land
limiting condition .........................................................................................................146
4.13 Cost and revenue curve under water limiting condition ..............................................149
18
List of Tables
3.1 Detail of irrigation treatments ..........................................................................................66
3.2 Calendar of operation of different cultural practices in different years ...........................68
4.1 Monthly average weather variables and ET0 for the crop seasons and
long-term average ............................................................................................................89
4.2 Number of irrigation and total water use under different treatments ...............................93
4.3 Leaf area index under different deficit treatments ...........................................................94
4.4 Chlorophyll content and reducing sugar of leaf during 2003-04 .....................................97
4.5 Chlorophyll content and reducing sugar of leaf during 2004-05 .....................................98
4.6 Component of ET under different treatments ................................................................101
4.7 Nutrient retention in soil under different irrigation strategies .......................................103
4.8 Growth and yield attributes of wheat under different treatments ..................................105
4.9 Correlation matrix of yield and yield components ........................................................106
4.10 Yield attributes and yield in pot experiment ................................................................107
4.11 Grain and straw yield under different treatments ........................................................109
4.12 Harvest ratio and harvest index under different treatments .........................................114
4.13 Irrigation amount and yield under different treatments ...............................................115
4.14 Crop coefficient of wheat under different ET0 methods in well irrigated treatments ..120
4.15 Crop coefficient of wheat in deficit treatment under different ET0 methods ................... 125
4.16 Crop coefficient for single-stage deficit ............................................................................. 128
4.17 Yield response factor for different growth stages .............................................................. 131
4.18 Sensitivity index (λ, of Jensen model) of wheat yield to water deficit at
various growth stages ....................................................................................................135
4.19 Simulated yield with CROPWAT and observed yield reduction .................................... 136
4.20 Water productivity and productivity of irrigation water under different treatments ....... 139
4.21 Average of water productivity and productivity of irrigation water
under different treatments ..............................................................................................140
4.22 Average of relative yield reduction and irrigation water savings
under different treatments ..............................................................................................143
19
4.23 (a) Partial budget analysis of wheat production without considering
opportunity cost of irrigation water ...............................................................................144
(b) Full budget analysis without considering opportunity cost of
irrigation water ..............................................................................................................143
4.24 (a) Partial budget analysis of wheat production considering opportunity
cost of irrigation water ...................................................................................................148
(b) Full budget analysis considering opportunity cost of irrigation water ...................149
20
List of Appendices 1.1 Long-term average of monthly total rainfall at two locations of Bangladesh ...............181
1.2 Water requirement of rice and wheat .............................................................................182
1.3 Trend of area, production and productivity of wheat and boro rice ..............................183
3.1 Cost of wheat production under non-irrigated condition (full budget analysis) ............184
3.2 Operating cost under different deficit strategies when opportunity
cost of irrigation is considered ......................................................................................185
4.1 Estimation of extra-terrestrial radiation .........................................................................186
4.2 Leaf water potential of leaf before 3rd irrigation during 2002-03 ..................................187
4.3 Root length density under different treatments during 2003-04 ....................................188
4.4 Root length density under different treatments during 2004-05 ....................................189
4.5 Soil moisture extraction pattern under different deficit strategies during 2002-03 .......190
4.6 Soil moisture extraction pattern under different deficit strategies during 2003-04 .......191
4.7 Soil moisture extraction pattern under different deficit strategies during 2004-05 .......192
4.8 Grain protein content under different treatments ...........................................................193
4.9 Crop coefficient of well irrigated treatment as a function of DFS
with combined data of ET0 methods .............................................................................194
4.10 Crop coefficient of well irrigated treatment as a function of growing-
degree-days (GDD) with combined data of ET0 methods ............................................195
4.11 Crop coefficient of deficit treatment as a function of DFS with
combined data of ET0 methods .....................................................................................196
21
List of Abbreviations
ASM Available soil moisture
BARI Bangladesh Agricultural Research Institute
BINA Bangladesh Institute of Nuclear Agriculture
CHU Crop heat unit
cm centimeter
CRI Crown root initiation
CSF Crop susceptibility
CWR Crop water requirement
DAS Days after sowing
DF Dilution factor
DMRT Duncan’s new multiple range text
ET Evapotranspiration
ETD Cumulative evapotranspiration deficit
FAO Food and Agricultural Organization
FC Field capacity
g gram
GDD Growing degree days
HUE Heat use efficiency
IW Irrigation water
kg Kilogram
LAI Leaf area index
LSD Least significant difference
m meter
ml milliliter
mm millimeter
nm nanometer
P-M Penman-Monteith
PTU Photothermal unit
RCB Randomized complete block
22
RLD Root length density
TSM Total profile soil moisture
UNESCO United Nations education, science and cultural organizations
vol. Volume
WP Wilting point
WUE Water use efficiency
23
List of Symbols
0C Centigrade temperature
A645 Absorbance at 645 nm wave length
A663 Absorbance at 663 nm wave length
cm/hr Centimeter per hour
cp Specific heat of air
E0 Evaporation of a free water surface
EET Water productivity
Eir Productivity of irrigation water
ET0 Reference evapotranspiration
ETa Actual crop evapotranspiration
ETc Crop evapotranspiration
ETm Maximum evapotranspiration
gm/cc Gram per cubic centimeter
ha Hectare
IW/CPE Ratio of irrigation water to cumulative evapotranspiration
K Potassium
kc Crop coefficient
Ky Yield response factor
kg/ha Killogram per hectare
kg/ha/day Killogram per hectare per day
kg/m3 Killogram per cubic meter
kPa Killo Pascal
log Logarithm to the base 10
m/sec Meter per second
m3/m3 Cubic meter per cubic meter
mg/gm Milligram per gram
MPir Marginam productivity of irrigation water
N Nitrogen
P Phosphorus
24
PH Soil reaction indication
R2 Coefficient of determination
Ra Extra-terrestrial radiation
Rs Global radiation
Sm-1 Second per meter
t/ha Metric ton per hectare
TB Base temperature
Tmax Maximum temperature
Tmean Mean temperature
Tmin Minimum temperature
v/v ratio of volume to volume
Wm-2 Weiber per square meter
Y Crop yield
Ya Actual yield
Ymax Maximum yield
Zn Zinc
θi Soil moisture content at ith layer
λ Sensitivity index of crop to water stress
Π Multiplication
ψ Leaf water potential
25
Chapter I
Introduction
1.1 General concept of irrigation
Plants need water for its proper growth and development. The demand for water by the
crop must be met by the water in the soil, via the root system. Application of water to
meet the crop water demand at proper time in proper way is termed as irrigation. If the
crop water demand is meet by other ways (such as rainfall, capillary rise from
groundwater table, etc.), there is no need of irrigation. Irrigation water requirement for
cereals and non-cereals are not same. Among cereals, irrigation water requirement of
rice is the highest. On the contrary, irrigation requirement of wheat is less compared to
rice. Proper irrigation scheduling also affects the irrigation requirement of different
crops.
1.1.1 Irrigation scheduling
The problem of irrigation scheduling consists of: (i) when to irrigate, (ii) how much to
irrigate, and (iii) how to apply irrigation water. The amount of irrigation is obtained
through field measurement or predicted through indirect method. The amount of
irrigation is defined as the depth of water needed to meet the crop water loss through
evapotranspiration under the growing environment. Although both timing and amount of
water applied affect irrigation water productivity, timing has the greatest effect on crop
yield and quality because at some growth stages, excessive soil moisture stress caused by
delayed irrigation can irreversibly reduce the potential yield or quality or both. Different