Development of Deficit Irrigation Scheduling Strategies for Maize Crop under Gravity-drip Irrigation System.
ABSTRACT
Among other ways of effective water strategies are the of a drip irrigation and the of a deficit scheduling strategy which is not common in the study area.
Effective water management is a key to improving agricultural water management, enhancing crop production, and improved the sustainability of irrigated agriculture.
In the past, the outcome of any water management strategy could only be known after field experiment, in recent times, means of evaluating the implications of irrigation schedules without field experiment is fast gaining grounds with the use of models.
However, there is need for proper evaluation of developed irrigation scheduling options with the use of models for optimal water management and crop response, before recommendations can be made to relevant bodies.
This research work presents scenarios studies for different developed irrigation scheduling options for a drip irrigated maize crop at the Institute for Agricultural Research (I.A.R) irrigation farm Samaru-Nigeria during 2012/2013 and 2013/2014 cropping season using a computer-based model.
The experiment consisted of eight (8) treatments replicated three times and laid in a randomized complete block design.
The water application was regulated at selected crop growth stages. The test crop was SAMMAZ 14 early maturity maize variety.
AquaCrop, a decision support model was calibrated and validated with data obtained from the field, and later used to simulate impact of developed scheduling strategies on yields, soil water balance, and water productivity of a drip-irrigated Maize.
TABLE OF CONTENTS
TITLE PAGE………………………………………….…………….……………………ii
DECLARATION…………………………………………………………………………………………………………iii
CERTIFICATION……………………………………………………………………………………………………….iv
DEDICATION……………………………………………………………………………………………………………..v
ACKNOWLEDGEMENT …………………………………………………………………………………………..vi
ABSTRACT……………………………………………………………………………………………………………….vii
TABLE OF CONTENTS……………………………………………………………………………………………iix
LIST OF TABLES ……………………………………………………………………………………………………. xiv
LIST OF FIGURES …………………………………………………………………………………………………. xvii
LIST OF PLATES…………………………………………………………………………………………………….. xix
LIST OF APPENDICES ……………………………………………………………………………………………. xx
LIST OF ACRONYMS AND ABBREVIATION…………………………………. xxi
CHAPTER ONE
1.0 INTRODUCTION…………………………………………………………………………………………………. 1
1.1Background of Study……………………………………………………………………………………………… 1
1.2Statement of the Problem……………………………………………………………………………………… 2
1.3Justification……………………………………………………………………………………………………………. 4
1.4Objectives ……………………………………………………………………………………………………………… 5
CHAPTER TWO
2.0 LITERATURE REVIEW …………………………………………………………………………………. 6
2.1 Drip Irrigation Hydraulics……………………………………………………………………………. 6
2.1.1 Measures of Discharge Uniformity (DU)………………………………………………. 8
2.1.2 Emitter flow variation …………………………………………………………………………… 8
2.1.3 Emission Uniformity………………………………………………………………………………… 8
2.1.4 Discharge Coefficient of Variation ……………………………………………………….. 9
2.1.5 Application Efficiency ………………………………………………………………………… 10
2.2 Determination of Irrigation Water Requirement …………………………………………….. 10
2.3 Deficit Irrigation Schedulling ………………………………………………………………………… 12
2.4 Growth- Stage Deficit Irrigation…………………………………………………………………….. 13
2.5 Growth Stages of Maize…………………………………………………………………………………. 14
2.6 Crop Evapotranspiration………………………………………………………………………………… 15
2.6.1 Crop water use ……………………………………………………………………………………….. 16
2.6.2 Crop yield and water use – – – – – 17
2.6.3 Soil Water Balance ………………………………………………………………………………… 19
2.6.4 Effective Rainfall…………………………………………………………………………………… 19
2.7 Crop Water Productivity………………………………………………………………………………….. 20
2.8 Economic Evalua…………………………………………………………… 20
2.9 The AquaCrop Model ……………………………………………………………………………………. 21
2.9.1 Sub-Models of AquaCrop……………………………………………………………………….. 25
2.9.2 AquaCrop Input Parameters…………………………………………………………………… 25
2.9.3 Outputs of AquaCrop Model …………………………………………………………………… 28
2.10 Validation and Calibration of Models……………………………………………………………. 29
2.10.1 Sensitivity Analysis ……………………………………………………………………………….. 31
2.10.2 Performance Evaluation of a Model …………………………………………………………. 32
CHAPTER THREE
3.0 MATERIALS AND METHODS……………………………………………………………………. 34
3.1 The Study Area ……………………………………………………………………………………………….. 34
3.2 Experimental Treatment Description ………………………………………………………………. 37
3.3 Experimental Layout and Agronomic Practices………………………………………………. 38
3.4 Irrigation Water Source and Drip Irrigation Hydraulics ………………………………….. 41
3.5 Emitter Discharge……………………………………………………………………………………………. 42
3.5.1 Soil Wetting Diameter ……………………………………………………………………………. 43
3.5.2 Water Application………………………………………………………………………………….. 45
3. 6 Computation of Soil moisture Content…………………………………………………………… 50
3.7 Canopy Cover Determination ………………………………………………………………………… 51
3.8 Above ground Biomass and Final Harvesting……………………………… 51
3.9 Statistical Analysis…………………………………………………………………………………………. 51
3.10 Running AquaCrop Model……………………………………………………………………………… 52
3.10.1 Calibration Procedure …………………………………………………………………………….. 53
3.10.2 Sensitivity Analysis ……………………………………………………………………………….. 55
3.10.3 Validation of the AquaCrop Model ………………………………………………………….. 56
3.10.4 Performance Evaluation of AquaCrop Model ……………………………………………. 56
3.11 Scenario Study on deficit Irrigation Scheduling on yield and water productivity of
maize ………………………………………………………………………………………………………………………… 57
3.12 Evaluation of Economic Performance………………………………………… 58
CHAPTER FOUR
4.0 RESULTS AND DISCUSSION ……………………………………………………………………… 61
4.1 Drip Irrigation Hydraulics performance Evaluation …………………………………………. 61
4.1.1 Emitter Flow Rate ……………………………………………………………. 63
4.1.2 Soil Wetting Capacities of Drippers…………………………………………….63
4.2 Grain and Biomass Yield……………………………………………………………………………….. 65
4.3 Soil Water Balance …………………………………………………………………………………………. 68
4.4 Irrigation Water productivity ………………………………………………………………………….. 70
4.5 Crop yield – Seasonal ET Relationship……………………………………………………………. 72
4.6 Relative Yield Decrease, Seasonal Crop water use deficit and yield response
factor ………………………………………………………………………………………………………………………… 73
4.7 AquaCrop Model Calibrations………………………………………………………………………….. 76
4.8 Model Validation……………………………………………………………………………………………… 81
4.8.1 Simulated Grain and Biomass Yield…………………………………………….. 81
4.8.2 Simulated Seasonal Evapotranspiration………………………………………… 84
4.8.3 Simulated Biomass and Grain Water Productivity……………………………… 84
4.8.4 Aboveground Biomass………………………………………………………….. 86
4.8.5 Canopy Cover Simulation……………………………………………………… 87
4.9 Sensitivity Analysis………………………………………………………………………………………….. 88
4.10 Effect of Deficit Irrigation on Benefit-cost Ratio of Drip Irrigated Maize…… 91
4.11 Scenario Study on Deficit Irrigation Scheduling for a Drip Irrigated Maize Crop
with AquaCrop Model……………………………………………………… 93
4.11.1 Effects of Varying Irrigation Intervals and Fixed Water Applied Depth…. 93
4.11.2 Effects of Irrigation Interval and Varied WAD on Yields and Water Balance
Response of Maize…………………………………………………………………… 106
4.11.3 Impact of Irrigation Intervals Beyond 3day at Some Crop Growth Stages… 101
4.11.4 Impacts of Plant Density on Crop Yield, Soil water Balance of Irrigated
Maize Crop………………………………………………………………… 106
4.12 Contribution to Knowledge………………………………………………… 107
CHAPTER FIVE
5.0 SUMMARY, CONCLUSION AND RECOMMENDATIONS……………………… 108
5.1 Summary……………………………………………………………………………………………………….. 108
5.2 Conclusion…………………………………………………………………………………………………….. 110
5.3 Recommendations ………………………………………………………………………………………….. 111
REFERENCES ……………………………………………………………………………………………………….. 112
INTRODUCTION
Management of irrigation water has become needful for the sustainability of agriculture in Nigeria. Some farmers in Nigeria irrigate until their fields are inundated; they seldom know the depth of water to apply per irrigation, which leads to flooding and a rise in the water table.
This call for a paradigm shift in the way irrigation is practiced in Nigeria from maximizing yield per unit area to the sustainability of irrigation as a whole;
which entails the adoption of effective irrigation water management strategies that could help to maximize yield per unit of water applied, minimizing energy requirement and maximizing the return for irrigation.
The call to improve the efficiency and productivity of water use for crop production has never been more urgent than now because of the emerging threat to the sustainability of agriculture (Kendall, 2011; Igbadun et al., 2012).
Some of the effective water management strategies are the use of drip irrigation systems and the adoption of deficit irrigation scheduling.
The drip irrigation system is one of the fastest expanding technologies in modern irrigated agriculture with great potential for achieving high effectiveness of water use. It allows judicious use of water and fertilizer during irrigation of a wide range of crops.
Deficit irrigation scheduling has been recognized as a viable practice that could lead to increased crop yield, reduced negative environmental impact and improved sustainability of irrigated agriculture.
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