There is a growing societal concern about excessive water and fertilizer use in agricultural systems. High water productivity while maintaining high crop yields can be achieved with appropriate irrigation scheduling. Moreover, freshwater pollution through nitrogen (N) leaching due to the widespread use of N fertilizers demands for an efficient N fertilization management. However, sustainable crop management requires good knowledge of soil water and N dynamics as well as of crop water and N demand.
Crop growth models, which describe physical and physiological processes of crop growth as well as water and matter transport, are considered as powerful tools to assist in the optimization of irrigation and fertilization management. It is of a general nature that the reliability of simulation based predictions depends on the quality and quantity of the data used for model calibration and validation which can be obtained e.g. in field experiments. A lack of data or low data quality for model calibration and validation may cause low performance and large uncertainties in simulation results. The large number of model parameters to be calibrated requires appropriate calibration methods and a sequential calibration strategy. Moreover, a simulation based planning of the field design saves costs and expenditure while supporting maximal outcomes of experiments. An adjustment of crop growth modeling and experiments is required for model improvement and development to reliably predict crop growth and to generalize predicted results. In this research study, a new approach for simulation based optimal experimental design was developed aiming to integrate simulation models, experiments, and optimization methods in one framework for optimal and sustainable irrigation and N fertilization management.
The approach is composed of three steps:
1. The preprocessing consists of the calibration and validation of the crop growth model based on existing experimental data, the generation of long time-series of climate data, and the determination of the optimal irrigation control.
2. The implementation comprises the determination and experimental application of the simulation based optimized deficit irrigation and N fertilization schedules and an appropriate experimental data collection.
3. The postprocessing includes the evaluation of the experimental results namely observed yield, water productivity (WP), nitrogen use efficiency (NUE), and economic aspects, as well as a model evaluation.
Five main tools were applied within the new approach: an algorithm for inverse model parametrization, a crop growth model for simulating crop growth, water balance and N balance, an optimization algorithm for deficit irrigation and N fertilization scheduling, and a stochastic weather generator. Furthermore, a water flow model was used to determine the optimal irrigation control functions and for simulation based estimation of the optimal field design. The approach was implemented within three case studies presented in this work.
The new approach combines crop growth modeling and experiments with stochastic optimization. It contributes to a successful application of crop growth modeling based on an appropriate experimental data collection. The presented model calibration and validation procedure using the collected data facilitates reliable predictions. The stochastic optimization framework for deficit irrigation and N fertilization scheduling proved to be a powerful tool to enhance yield, WP, NUE and profit.:Contents
Nomenclature ..............................................................................................................................xii
1 Introduction..................................................................................................................................1
I Fundamentals and literature review ........................................................................................5
2 Water productivity in crop production ....................................................................................7
2.1 Water productivity .................................................................................................................7
2.2 Increase of crop yield ..........................................................................................................9
2.3 Irrigation ...............................................................................................................................10
2.3.1 Irrigation methods ...........................................................................................................10
2.3.2 Irrigation scheduling and irrigation control ................................................................11
2.3.3 The influence of the field design on profitability .......................................................12
2.4 The concept of controlled deficit irrigation ...................................................................14
3 Nitrogen use efficiency in crop production .........................................................................17
3.1 Nitrogen use efficiency ....................................................................................................18
3.2 N fertilization management .............................................................................................18
3.3 Combination of controlled deficit irrigation and deficit N fertilization ......................19
4 Crop growth modeling ............................................................................................................21
4.1 Physiological crop growth models ..................................................................................21
4.1.1 Model description of SVAT model Daisy ....................................................................22
4.1.2 Model description of crop growth model Pilote .........................................................24
4.2 Optimal experimental design for model parametrization ...........................................25
4.2.1 Experimental design ......................................................................................................25
4.2.2 Model parameter estimation ........................................................................................26
4.2.3 Model parameter estimation based on greenhouse data .......................................27
5 Irrigation and N fertilization scheduling ..............................................................................29
5.1 Irrigation scheduling .........................................................................................................29
5.2 N fertilization scheduling .................................................................................................30
5.3 Combination of irrigation and N fertilization scheduling ............................................30
II New approach for simulation based optimal experimental design ................................33
6 Preprocessing steps ...............................................................................................................37
6.1 Model parametrization and assessment .......................................................................37
6.1.1 Calibration of the soil parameters ...............................................................................38
6.1.2 Calibration of the plant parameters ............................................................................39
6.1.3 Model assessment .........................................................................................................41
6.1.4 Preliminary simulations for an optimal experimental layout ..................................43
6.2 Generation of long time-series of climate data ............................................................44
6.3 Determination of the optimal irrigation control functions ...........................................44
7 Stochastic optimization framework ......................................................................................47
7.1 Stochastic optimization framework .................................................................................47
7.1.1 Optimization algorithm ...................................................................................................47
7.1.2 Generation of the crop water (nitrogen) production functions ................................48
7.1.3 Application of the stochastic optimization framework ..............................................48
7.1.4 Crop growth model requirements ................................................................................49
8 Data collection during the experimentation .......................................................................51
9 Postprocessing steps .............................................................................................................55
9.1 Evaluation of the experimental results ...........................................................................55
9.1.1 Yield and total dry matter ..............................................................................................55
9.1.2 Water productivity and nitrogen use efficiency .........................................................55
9.1.3 Economic aspects ..........................................................................................................55
9.1.4 Evaluation of the model results ....................................................................................56
III Application of the new approach to three case studies ...................................................57
10 Evaluation of model transferability ....................................................................................59
10.1 Objectives and summary ................................................................................................59
10.2 Experimental site and experimental setup .................................................................61
10.3 Data collection during the experimentation ................................................................63
10.4 Calibration and validation of the model parameters .................................................63
10.4.1 Model setup and soil parametrization ......................................................................64
10.4.2 Plant parameter calibration and validation .............................................................67
10.5 Application of the stochastic optimization framework ...............................................75
10.5.1 Generation of the climate data ...................................................................................75
10.5.2 Estimation of the yield potential of wheat ................................................................75
10.5.3 Estimation of the water productivity potential of barley .........................................77
10.6 Discussion and conclusions ..........................................................................................81
11 Real-time irrigation scheduling ..........................................................................................83
11.1 Objectives and summary ................................................................................................83
11.2 Experimental site and field design ...............................................................................85
11.3 Data collection during the experiment ........................................................................86
11.4 Calibration and setup of the crop growth model Pilote .............................................87
11.5 Derivation of optimal irrigation control functions for different drip line spacings 88
11.5.1 Initial Hydrus 2D/3D simulations ...............................................................................88
11.5.2 Determination of the irrigation control functions .....................................................89
11.5.3 Verifying measurements ..............................................................................................92
11.6 Real-time deficit irrigation scheduling .........................................................................93
11.7 Evaluation of the experimental results .........................................................................96
11.7.1 Crop yields .....................................................................................................................96
11.7.2 Water productivity .........................................................................................................97
11.7.3 Prognostic simulations ................................................................................................98
11.7.4 Economic aspects ........................................................................................................99
11.8 Discussion and conclusions ........................................................................................100
12 Multicriterial optimization...................................................................................................103
12.1 Objectives and summary .............................................................................................103
12.2 Experimental site and experimental setup ...............................................................105
12.3 Data collection during the experiment ......................................................................105
12.4 Experimental layout ......................................................................................................106
12.5 Calibration and validation of the model parameters ..............................................107
12.5.1 Calibration of the soil parameters ...........................................................................107
12.5.2 Calibration and validation of the plant parameters .............................................107
12.5.3 Setup of SVAT model Daisy .....................................................................................108
12.6 Generation of the climate data ....................................................................................109
12.7 Optimized irrigation and N fertilization scheduling .................................................109
12.8 Evaluation of the experimental results .......................................................................111
12.8.1 Observed plant variables and weather data .........................................................111
12.8.2 Water productivities and nitrogen use efficiencies ...............................................111
12.8.3 Chlorophyll Meter values ..........................................................................................112
12.8.4 Recalculation of soil parameters .............................................................................113
12.9 Postprocessing simulations of yield and water and N dynamics..........................114
12.9.1 Yield predictions using Daisy 1D ............................................................................114
12.9.2 Yield predictions using Daisy 2D ............................................................................119
12.10 Discussion and conclusions .....................................................................................121
IV General discussion, conclusions and outlook ...............................................................123
13 General discussion ............................................................................................................125
14 General conclusions and outlook ....................................................................................133
Appendix ....................................................................................................................................134
A Tables and Figures ...............................................................................................................137
B Model setup and weather files ...........................................................................................145
List of Tables .............................................................................................................................153
List of Figures ............................................................................................................................153
References ................................................................................................................................159 / In der heutigen Gesellschaft gibt es zunehmend Bedenken gegenüber übermäßigem Wasser- und Düngereinsatz in der Landwirtschaft. Eine hohe Wasserproduktivität kann jedoch durch geeignete Bewässerungspläne mit hohen landwirtschaftlichen Erträgen in Einklang gebracht werden. Die mit der weitverbreiteten Stickstoffdüngung einhergehende Gewässerbelastung aufgrund von Stickstoffauswaschung erfordert zudem ein effizientes Stickstoffmanagement. Eine entsprechende ressourceneffiziente Landbewirtschaftung bedarf präzise Kenntnisse der Bodenwasser- und Stickstoffdynamiken sowie des Pflanzenwasser- und Stickstoffbedarfs.
Als leistungsfähige Werkzeuge zur Unterstützung bei der Optimierung von Bewässerungs-und Düngungsplänen werden Pflanzenwachstumsmodelle eingesetzt, welche die physischen und physiologischen Prozesse des Pflanzenwachstums sowie die physikalischen Prozesse des Wasser- und Stofftransports abbilden. Hierbei hängt die Zuverlässigkeit dieser simulationsbasierten Vorhersagen von der Qualität und Quantität der bei der Modellkalibrierung und -validierung verwendeten Daten ab, welche beispielsweise in Feldversuchen erfasst werden. Fehlende Daten oder Daten mangelhafter Qualität bei der Modellkalibrierung und -validierung führen zu unzuverlässigen Simulationsergebnissen und großen Unsicherheiten bei der Vorhersage. Die große Anzahl an zu kalibrierenden Parametern erfordert zudem geeignete Kalibrierungsmethoden sowie eine sequenzielle Kalibrierungsstrategie. Darüber hinaus kann eine simulationsbasierte Planung des Versuchsdesigns Kosten und Aufwand reduzieren und zu weiteren experimentellen Erkenntnissen führen. Die Abstimmung von Pflanzenwachstumsmodellen und Versuchen ist zudem für die Modellentwicklung und -verbesserung sowie für eine Verallgemeinerung von Simulationsergebnissen unabdingbar. Im Rahmen dieser Arbeit wurde ein neuer Ansatz für ein simulationsbasiertes optimales Versuchsdesign entwickelt. Ziel war es, Simulationsmodelle, Versuche und Optimierungsmethoden in einem Ansatz für optimales und nachhaltiges Bewässerungs- und Düngungsmanagement zu integrieren.
Der Ansatz besteht aus drei Schritten:
1. Die Vorbereitungsphase beinhaltet die auf existierenden Versuchsdaten basierende Kalibrierung und Validierung des Pflanzenwachstumsmodells, die Generierung von Klimazeitreihen und die Bestimmung der optimalen Bewässerungssteuerung.
2. Die Durchführungsphase setzt sich aus der Erstellung und experimentellen Anwendung der simulationsbasierten optimierten Defizitbewässerungs- und Stickstoffdüngungspläne und der Erfassung der relevanten Versuchsdaten zusammen.
3. Die Auswertungsphase schließt eine Evaluierung der Versuchsergebnisse anhand ermittelter Erträge, Wasserproduktivitäten (WP), Stickstoffnutzungseffizienzen (NUE) und ökonomischer Aspekte, sowie eine Modellevaluierung ein.
In dem neuen Ansatz kamen im Wesentlichen folgende fünf Werkzeuge zur Anwendung: Ein Algorithmus zur inversen Modellparametrisierung, ein Pflanzenwachstumsmodell, welches das Pflanzenwachstum sowie die Wasser- und Stickstoffbilanzen abbildet, ein evolutionärer Optimierungsalgorithmus für die Generierung von defizitären Bewässerungs- und Stickstoffplänen und ein stochastischer Wettergenerator. Zudem diente ein Bodenwasserströmungsmodell der Ermittlung der optimalen Bewässerungssteuerung und der simulationsbasierten Optimierung des Versuchsdesigns. Der in dieser Arbeit vorgestellte Ansatz wurde in drei Fallbeispielen angewandt.
Der neue Ansatz kombiniert Pflanzenwachstumsmodellierung und Experimente mit stochastischer Optimierung. Er leistet einen Beitrag zu einer erfolgreichen Pflanzenwachstumsmodellierung basierend auf der Erfassung relevanter Versuchsdaten. Die vorgestellte Modellkalibrierung und -validierung unter Verwendung der erfassten Versuchsdaten trug wesentlich zu zuverlässigen Simulationsergebnissen bei. Darüber hinaus stellt die hier vorgestellte stochastische Optimierung von defizitären Bewässerungs- und Stickstoffplänen ein leistungsfähiges Werkzeug dar, um Erträge, WP, NUE und den Profit zu erhöhen.:Contents
Nomenclature ..............................................................................................................................xii
1 Introduction..................................................................................................................................1
I Fundamentals and literature review ........................................................................................5
2 Water productivity in crop production ....................................................................................7
2.1 Water productivity .................................................................................................................7
2.2 Increase of crop yield ..........................................................................................................9
2.3 Irrigation ...............................................................................................................................10
2.3.1 Irrigation methods ...........................................................................................................10
2.3.2 Irrigation scheduling and irrigation control ................................................................11
2.3.3 The influence of the field design on profitability .......................................................12
2.4 The concept of controlled deficit irrigation ...................................................................14
3 Nitrogen use efficiency in crop production .........................................................................17
3.1 Nitrogen use efficiency ....................................................................................................18
3.2 N fertilization management .............................................................................................18
3.3 Combination of controlled deficit irrigation and deficit N fertilization ......................19
4 Crop growth modeling ............................................................................................................21
4.1 Physiological crop growth models ..................................................................................21
4.1.1 Model description of SVAT model Daisy ....................................................................22
4.1.2 Model description of crop growth model Pilote .........................................................24
4.2 Optimal experimental design for model parametrization ...........................................25
4.2.1 Experimental design ......................................................................................................25
4.2.2 Model parameter estimation ........................................................................................26
4.2.3 Model parameter estimation based on greenhouse data .......................................27
5 Irrigation and N fertilization scheduling ..............................................................................29
5.1 Irrigation scheduling .........................................................................................................29
5.2 N fertilization scheduling .................................................................................................30
5.3 Combination of irrigation and N fertilization scheduling ............................................30
II New approach for simulation based optimal experimental design ................................33
6 Preprocessing steps ...............................................................................................................37
6.1 Model parametrization and assessment .......................................................................37
6.1.1 Calibration of the soil parameters ...............................................................................38
6.1.2 Calibration of the plant parameters ............................................................................39
6.1.3 Model assessment .........................................................................................................41
6.1.4 Preliminary simulations for an optimal experimental layout ..................................43
6.2 Generation of long time-series of climate data ............................................................44
6.3 Determination of the optimal irrigation control functions ...........................................44
7 Stochastic optimization framework ......................................................................................47
7.1 Stochastic optimization framework .................................................................................47
7.1.1 Optimization algorithm ...................................................................................................47
7.1.2 Generation of the crop water (nitrogen) production functions ................................48
7.1.3 Application of the stochastic optimization framework ..............................................48
7.1.4 Crop growth model requirements ................................................................................49
8 Data collection during the experimentation .......................................................................51
9 Postprocessing steps .............................................................................................................55
9.1 Evaluation of the experimental results ...........................................................................55
9.1.1 Yield and total dry matter ..............................................................................................55
9.1.2 Water productivity and nitrogen use efficiency .........................................................55
9.1.3 Economic aspects ..........................................................................................................55
9.1.4 Evaluation of the model results ....................................................................................56
III Application of the new approach to three case studies ...................................................57
10 Evaluation of model transferability ....................................................................................59
10.1 Objectives and summary ................................................................................................59
10.2 Experimental site and experimental setup .................................................................61
10.3 Data collection during the experimentation ................................................................63
10.4 Calibration and validation of the model parameters .................................................63
10.4.1 Model setup and soil parametrization ......................................................................64
10.4.2 Plant parameter calibration and validation .............................................................67
10.5 Application of the stochastic optimization framework ...............................................75
10.5.1 Generation of the climate data ...................................................................................75
10.5.2 Estimation of the yield potential of wheat ................................................................75
10.5.3 Estimation of the water productivity potential of barley .........................................77
10.6 Discussion and conclusions ..........................................................................................81
11 Real-time irrigation scheduling ..........................................................................................83
11.1 Objectives and summary ................................................................................................83
11.2 Experimental site and field design ...............................................................................85
11.3 Data collection during the experiment ........................................................................86
11.4 Calibration and setup of the crop growth model Pilote .............................................87
11.5 Derivation of optimal irrigation control functions for different drip line spacings 88
11.5.1 Initial Hydrus 2D/3D simulations ...............................................................................88
11.5.2 Determination of the irrigation control functions .....................................................89
11.5.3 Verifying measurements ..............................................................................................92
11.6 Real-time deficit irrigation scheduling .........................................................................93
11.7 Evaluation of the experimental results .........................................................................96
11.7.1 Crop yields .....................................................................................................................96
11.7.2 Water productivity .........................................................................................................97
11.7.3 Prognostic simulations ................................................................................................98
11.7.4 Economic aspects ........................................................................................................99
11.8 Discussion and conclusions ........................................................................................100
12 Multicriterial optimization...................................................................................................103
12.1 Objectives and summary .............................................................................................103
12.2 Experimental site and experimental setup ...............................................................105
12.3 Data collection during the experiment ......................................................................105
12.4 Experimental layout ......................................................................................................106
12.5 Calibration and validation of the model parameters ..............................................107
12.5.1 Calibration of the soil parameters ...........................................................................107
12.5.2 Calibration and validation of the plant parameters .............................................107
12.5.3 Setup of SVAT model Daisy .....................................................................................108
12.6 Generation of the climate data ....................................................................................109
12.7 Optimized irrigation and N fertilization scheduling .................................................109
12.8 Evaluation of the experimental results .......................................................................111
12.8.1 Observed plant variables and weather data .........................................................111
12.8.2 Water productivities and nitrogen use efficiencies ...............................................111
12.8.3 Chlorophyll Meter values ..........................................................................................112
12.8.4 Recalculation of soil parameters .............................................................................113
12.9 Postprocessing simulations of yield and water and N dynamics..........................114
12.9.1 Yield predictions using Daisy 1D ............................................................................114
12.9.2 Yield predictions using Daisy 2D ............................................................................119
12.10 Discussion and conclusions .....................................................................................121
IV General discussion, conclusions and outlook ...............................................................123
13 General discussion ............................................................................................................125
14 General conclusions and outlook ....................................................................................133
Appendix ....................................................................................................................................134
A Tables and Figures ...............................................................................................................137
B Model setup and weather files ...........................................................................................145
List of Tables .............................................................................................................................153
List of Figures ............................................................................................................................153
References ................................................................................................................................159
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:26293 |
| Date | 26 March 2012 |
| Creators | Seidel, Sabine |
| Contributors | Schmitz, Gerd Hans, Schmidhalter, Urs, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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