Microirrigation for Crop Production (eBook)

Front Cover 1
Preface 6
Contributors 7
Table of Contents 12
PART I. MICROIRRIGATION THEORY AND DESIGN PRINCIPLES 26
CHAPTER 1. INTRODUCTION 26
1.1. DEFINITION 26
1.2. HISTORY AND CURRENT STATUS 27
1.2.1. Early History Worldwide 27
1.2.2. Early History in United States 29
1.2.3. Current Irrigated Area 30
1.2.4. Principal Crops Utilizing Microirrigation 30
1.2.5. Trends 32
1.2.6. Economics 33
1.2.7. Expansion in Developing Countries 33
1.3. GENERAL PRINCIPLES 33
1.3.1. Advantages 34
1.3.1.1. Increased water use efficiency 34
1.3.1.1.1. Improved crop yields and quality 35
1.3.1.1.2. Reduced nonbeneficial use 35
1.3.1.1.3. Reduced deep percolation 35
1.3.1.2. Use of saline water 35
1.3.1.3. Improved fertilizer and other chemical application 36
1.3.1.4. Decreased energy requirements 36
1.3.1.5. Improved cultural practices 37
1.3.1.6. Use of biological effluent and treated wastewaters 37
1.3.2. Disadvantages 37
1.3.2.1. Extensive maintenance requirements 37
1.3.2.2. Salt accumulation near plants 38
1.3.2.3. Restricted root development 38
1.3.2.4. High system costs 39
1.3.2.5. Restricted crop rotation 39
1.3.3. System Considerations 39
1.3.3.1. Design and installation considerations 39
1.3.3.2. Maintenance considerations 39
1.3.3.3. Management considerations 39
1.3.3.4. Economic considerations 40
1.3.3.4.1. System costs 40
1.4. SYSTEM COMPONENTS 40
1.4.1. Emission Devices 41
1.4.2. Distribution System 41
1.4.3. Control and Automation 43
1.4.4. Filtration 44
1.5. SYSTEM TYPES 44
1.5.1. Surface Drip Irrigation 44
1.5.2. Subsurface Drip Irrigation 46
1.5.3. Bubbler Irrigation 47
1.5.4. Microsprinkler Irrigation 48
REFERENCES 49
CHAPTER 2. SOIL WATER CONCEPTS 52
2.1. INTRODUCTION 52
2.1.1. Soil Water Regime for High Frequency Irrigation 52
2.2. SOIL WATER 52
2.2.1. Soil Water Content 52
2.2.2. Soil Water Potential 53
2.2.3. Soil Water Characteristic Curves 55
2.2.4. Soil Water Measurements 56
2.2.4.1. Gravimetric determination of soil water content 57
2.2.4.2. Neutron scattering 57
2.2.4.3. Time domain reflectometry (TDR) 57
2.2.4.4. Tensiometers 57
2.2.4.5. Heat dissipation 58
2.2.4.6. Electrical resistance 58
2.2.4.7. Capacitance 58
2.3. SOIL WATER MOVEMENT 58
2.3.1. Darcy’s Law 58
2.3.1.1. Alternative forms for Darcy’s Law 59
2.3.2. Richards’ Equation 60
2.3.3. Measurements of Soil Hydraulic Parameters 61
2.3.3.1. Direct measurements 62
2.3.3.2. Indirect measurements 62
2.3.3.3. Inverse methods 62
2.3.4. Shortcuts with Pedotransfer Functions 62
2.4. MODELING FOR EFFECTIVE MANAGEMENT AND DESIGN 63
2.4.1. Simplified Hemispherical Model 63
2.4.2. Quasi-Linear Solutions to Richards’ Equation 64
2.4.2.1. Steady state solutions for point sources 66
2.4.2.2. Steady state solutions for surface ponding 68
2.4.2.3. Steady state solutions for line sources 69
2.4.2.4. Transient (time-dependent) solutions 70
2.4.3. Root Water Uptake 70
2.4.3.1. Transient two and three-dimensional uptake functions 76
2.4.4. Influence of Soil Spatial Variability on Soil Water Distribution 78
ACKNOWLEDGMENTS 81
LIST OF TERMS AND SYMBOLS 81
REFERENCES 82
CHAPTER 3. IRRIGATION SCHEDULING 86
3.1. INTRODUCTION 86
3.1.1. System Capacity 87
3.1.2. System Uniformity Effects on Scheduling 87
3.1.3. System Maintenance Effects on Scheduling 89
3.1.4. Scheduling Constraints 90
3.2. IRRIGATION SCHEDULING TECHNIQUES 91
3.2.1 Water Balance (Evapotranspiration Base) 91
3.2.1.1. Climatic factors affecting crop water use 93
3.2.1.2. Crop factors affecting ET 96
3.2.1.3. Soil factors affecting ET 107
3.2.1.4. A direct ET approach 111
3.2.1.5. Evaporation pans and atmometers 112
3.2.1.6. Scheduling principles using evapotranspiration 116
3.2.2. Soil Water Control 121
3.2.2.1. Soil water measurement and controls 123
3.2.2.2. Placement and implementation 128
3.2.3. Plant Water Deficit Indicators 128
3.2.3.1. Irrigation scheduling feedback loop using plant stress indicators 128
3.2.3.2. Plant water potential measurements 129
3.2.3.3. Plant size changes from plant-water stress 132
3.2.3.4. Plant stress based on plant temperature 133
3.2.3.5. Transpiration measurements by sap flow 134
3.3. SUMMARY 137
LIST OF TERMS AND SYMBOLS 138
REFERENCES 143
CHAPTER 4. SALINITY 156
4.1. INTRODUCTION 156
4.2. QUANTIFYING SALINITY AND SODICITY 157
4.2.1. Salinity 157
4.2.2. Sodicity 158
4.3. CROP TOLERANCE 159
4.3.1. Crop Salt Tolerance 160
4.3.2. Factors Modifying Salt Tolerance 162
4.3.3. Tolerance to Specific Solutes 163
4.4. LEACHING 164
4.4.1. Leaching Requirement 165
4.4.2. Impact of Rainfall 167
4.5. INFLUENCES OF IRRIGATION SYSTEM AND WATER SOURCE ON SOIL SALINITY 169
4.5.1. Influence of Irrigation Method 170
4.5.2. Reuse and Conjunctive Use of Waters 173
4.5.2.1. Reuse 173
4.5.2.2. Blending 174
4.5.2.3. Cycling 174
4.5.3. Environmental Consequences 175
4.6. SALINITY MANAGEMENT PRACTICES 175
4.6.1. Soil Salinity Distribution 175
4.6.2. Crop Considerations 177
4.6.2.1. Crop selection 177
4.6.2.2. Other management techniques 177
4.6.3. Infiltration 177
4.6.4. Reclamation of Salt-Affected Soils 178
4.6.4.1. Saline soils 178
4.6.4.2. Sodic soils 180
4.6.4.3. Boron leaching 182
4.7. SUMMARY AND CONCLUSIONS 182
REFERENCES 182
CHAPTER 5. GENERAL SYSTEM DESIGN PRINCIPLES 186
5.1. OVERVIEW OF THE DESIGN PROCESS 186
5.1.1. Initial Assessment 186
5.1.2. Microirrigation Layout and Components 188
5.1.3. The Design Process 190
5.2. SOURCES OF WATER 195
5.2.1. Water Quantity and Quality 195
5.2.2. Groundwater 196
5.2.3. Surface Water 196
5.3. SYSTEM HYDRAULICS 197
5.3.1. Hydraulic Principles 197
5.3.1.1. Total head 198
5.3.1.2. Pump energy requirements 200
5.3.1.3. Total friction head 201
5.3.1.3.1. Pipeline friction head loss 202
5.3.1.3.2. Multiple outlet pipes 204
5.3.1.3.3. Fitting, valve and component losses 211
5.3.1.3.4. Emitter connection losses 214
5.3.2. Emitter Hydraulics 216
5.3.3. Microirrigation Lateral Lines 221
5.3.3.1. Lateral line design procedures 228
5.3.4. Manifolds 231
5.3.5. Mainline Pipe System Design 235
5.4. FILTRATION 238
5.5 SUMMARY OF THE DESIGN PROCESS 239
ACKNOWLEDGEMENTS 240
LIST OF TERMS AND SYMBOLS 240
REFERENCES 243
SUPPLEMENTAL READING 244
CHAPTER 6. ECONOMIC IMPLICATIONS OF MICROIRRIGATION 246
6.1. INTRODUCTION 246
6.1.1. The Farm-Level Perspective 246
6.1.2. The Public Perspective 248
6.2. FARM-LEVEL COSTS OF MICROIRRIGATION 248
6.2.1. Fixed and Variable Costs 248
6.2.2. Examples from the Literature 249
6.2.2.1. Irrigating vegetables in Florida 249
6.2.2.2. Irrigating field crops with subsurface drip irrigation systems 251
6.2.2.3. Other examples 254
6.3. FARM-LEVEL BENEFITS OF MICROIRRIGATION 256
6.3.1. Crop Yield Effects 256
6.3.1.1. Deciduous fruits and nuts 256
6.3.1.2. Citrus 257
6.3.1.3. Small fruits 257
6.3.1.4. Tomato 258
6.3.1.5. Melons 259
6.3.1.6. Other fruits and vegetables 260
6.3.1.7. Cotton 262
6.3.1.8. Sugarcane and sugarbeets 264
6.3.2. Frost and Freeze Protection with Microsprinklers 265
6.3.3. Fertigation 266
6.3.4. Chemical Application of Non-Fertilizer Materials 267
6.3.5. Irrigation with Saline Water and Effluent 268
6.4. FARM-LEVEL OBSERVATIONS 270
6.5. PUBLIC BENEFITS AND POLICY IMPLICATIONS 272
6.6. SUMMARY 273
ACKNOWLEDGEMENTS 274
REFERENCES 274
PART II. OPERATION AND MAINTENANCE PRINCIPLES 284
CHAPTER 7. AUTOMATION 284
7.1. INTRODUCTION 284
7.2. CONTROL THEORY 285
7.2.1. Control Methods 285
7.2.1.1. On-off control 285
7.2.1.2. Stepwise control 287
7.2.1.3. Continuous control 288
7.2.2. Linear Systems 288
7.3. AUTOMATIC CONTROL SYSTEMS 288
7.3.1. Soil Water Methods 290
7.3.1.1. Soil water potential 290
7.3.1.2. Soil water content 293
7.3.1.3. Wetting front detection 295
7.3.2. Plant Water Methods 297
7.3.2.1. Leaf water potential method 298
7.3.2.2. Plant canopy temperature method 298
7.3.2.3. Plant turgor methods 300
7.3.2.4. Evapotranspiration estimates 302
7.3.2.4.1. Evapotranspiration models 302
7.3.2.4.2. Direct measurement of Etc 303
7.4. INSTRUMENTATION AND HARDWARE 304
7.4.1. Controllers 305
7.4.2. Valves 305
7.4.3. Flowmeters 305
7.4.4. Environmental Sensors 305
7.4.5. Filters 306
7.4.6. Chemical Injectors 306
7.5. SUMMARY 306
REFERENCES 306
CHAPTER 8. APPLICATION OF CHEMICAL MATERIALS 310
8.1. INTRODUCTION 310
8.1.1. Definitions 310
8.1.2. Basic Information 311
8.1.3. Advantages of Chemigation 311
8.1.4. Disadvantages of Chemigation 312
8.1.5. Types of Agrochemicals 313
8.1.5.1. Water soluble chemicals 313
8.1.5.2. Wettable powders 313
8.1.5.3. Emulsifiable (oil soluble) chemicals 313
8.1.5.4. Gases 314
8.1.6. Safety 314
8.1.6.1. Following the label and other regulations 314
8.1.7. General Considerations 315
8.1.7.1. Problems with chemical mixes 317
8.2. CHEMICAL INJECTION METHODS 319
8.2.1. Injection Pumps and Systems 319
8.2.2. Pollution Prevention 322
8.2.2.1. Electrical and mechanical interlock system 323
8.2.2.2. Backflow prevention in the irrigation line 323
8.2.2.3. Injection line components 325
8.2.3. Chemical Supply Tanks and Secondary Containment 327
8.2.4. Corrosion Resistance of Surfaces 327
8.2.5. Maintenance 329
8.3. CHEMICALS AND CALCULATION OF INJECTION RATES 329
8.3.1. Fertigation 329
8.3.1.1. Calculation of plant nutrient requirements 330
8.3.1.2. Fertilizer selection and calculation of injection rates 341
8.3.2. Chemigation of Non-Fertilizer Materials 350
REFERENCES 351
CHAPTER 9. APPLICATION OF BIOLOGICAL EFFLUENT 354
9.1. INTRODUCTION 354
9.1.1. Advantages of Applying Biological Effluent 355
9.1.2. Disadvantages of Applying Biological Effluent 356
9.2. CHARACTERISTICS OF BIOLOGICAL EFFLUENTS 356
9.2.1. Effluent Source and Degree of Treatment 356
9.2.2. Composition of Effluent 358
9.2.3. Characteristics of Effluents Used in Some Microirrigation Studies 359
9.3. BIOLOGICAL EFFLUENT CONSTITUENT BEHAVIOR IN SOILS 360
9.3.1. Nitrogen Uptake by Plants and Potential Loss Mechanisms 360
9.3.2. Phosphorus Uptake by Plants and Potential Loss Mechanisms 362
9.3.3. Trace Element Uptake by Plants and Potential Loss Mechanisms 363
9.3.4. Salinity Management 365
9.3.5. Pathogenic Organisms 365
9.4. HEALTH CONSIDERATIONS 366
9.4.1. Typical Regulations 366
9.4.2. Practices to Meet the Regulations 368
9.5. SITE CONSIDERATIONS 368
9.5.1. Soils 369
9.5.2. Climate 369
9.5.3. Crops 370
9.5.4. Land Area 371
9.6. DESIGN AND MANAGEMENT CONSIDERATIONS 372
9.6.1. System Components 372
9.6.2. Filtration Requirements 374
9.6.3. Chemical Treatment Requirements 376
9.6.4. Dripline Flushing 377
9.6.5. Monitoring Procedures 377
ACKNOWLEDGEMENTS 377
REFERENCES 378
CHAPTER 10. FIELD PERFORMANCE AND EVALUATION 382
10.1. INTRODUCTION 382
10.1.1. Uniformity of Water Application 382
10.1.2. Order of Significance of Design Parameters 383
10.1.3. The Goal of Microirrigation Application 384
10.2. VARIATIONS OF IRRIGATION APPLICATION 384
10.2.1. Variations from Hydraulic Design 384
10.2.2. Manufacturer’s Variation 385
10.2.3. Effects by Grouping of Emitters 385
10.2.4. Possible Clogging Effects 386
10.2.5. Total Variation 387
10.3. UNIFORMITY CONSIDERATIONS 387
10.3.1. Uniformity Parameters 387
10.3.2. A Linearized Water Application Function 388
10.3.3. Uniformity and Total Yield 390
10.3.4. Uniformity and Total Economic Return 392
10.4. FIELD PERFORMANCE AND IRRIGATION STRATEGY 394
10.4.1. Significance of Irrigation Scheduling 394
10.4.2. Optimal Irrigation 395
10.4.3. Conventional Irrigation 395
10.4.4. A Simple Irrigation Schedule 396
10.4.5. Irrigation Strategy for Environmental Protection 396
10.4.6. Microirrigation for Water Conservation 397
10.4.6.1. Comparing optimal schedule with conventional irrigation schedule 397
10.4.6.2. Comparing simple irrigation schedule with conventional irrigation schedule 397
10.4.6.3. Comparing simple irrigation schedule with the optimal irrigation schedule 398
10.4.6.4. Comparing the irrigation schedule for environmental protection with the optimal irrigation schedule 398
10.4.6.5. Comparing the irrigation schedule for environmental protection with the simple irrigation schedule 398
10.5. FIELD EVALUATION AND ADJUSTMENT 401
10.5.1. Design Criteria of Microirrigation 401
10.5.1.1 Uniformity parameters 401
10.5.1.2. Determination of design criteria 403
10.5.1.3. Selection of design criteria 405
10.5.2. Field Evaluation 405
10.5.2.1. Significance of field evaluation 405
10.5.2.2. Uniformity measurement 406
10.5.3. Repairs and Adjustment 406
10.5.3.1. Repairing leaks in the system 406
10.5.3.2. Adjustment of irrigation time 407
10.5.3.3. Adjustments for changes in uniformity 408
LIST OF TERMS AND SYMBOLS 408
REFERENCES 411
CHAPTER 11. MAINTENANCE 414
11.1. EMITTER OPERATION 414
11.1.1. Evaluation of Emitter Clogging 414
11.1.1.1. Source of water 414
11.1.1.2. Surface water 416
11.1.1.3. Groundwater 417
11.1.1.4. Wastewater 417
11.1.2. Water Quality 418
11.1.2.1. Physical aspects 418
11.1.2.2. Chemical aspects 419
11.1.2.3. Biological aspects 420
11.1.3. Causes 422
11.1.3.1. Physical, chemical, and biological factors 422
11.1.3.2. Microorganisms 422
11.1.3.3. Macroorganisms 426
11.2. WATER TREATMENT 427
11.2.1. Filtration 428
11.2.1.1. Screen filters 429
11.2.1.2. Disk filters 432
11.2.1.3. Media filters 432
11.2.1.4. Settling basins 435
11.2.1.5. Cyclonic filters or centrifugal separators 437
11.2.1.6. Filter design and operation 437
11.2.2. Chemical Treatment 437
11.2.2.1. Chemical precipitation 437
11.2.2.2. Acid treatment 439
11.2.2.3. Chlorination 441
11.2.2.4. Chemical injection 445
11.3. MAINTENANCE OPERATION 445
11.3.1. Approach 445
11.3.1.1. Chemical water treatment research 446
11.3.1.2. Preventive maintenance practices 447
11.3.1.3. Flushing 450
11.3.1.4. Reclamation 452
11.4. GUIDELINE AND PRACTICES 452
REFERENCES 452
SUPPLEMENTAL READING 455
PART III. SYSTEM TYPE AND MANAGEMENT PRINCIPLES 456
CHAPTER 12. SURFACE DRIP IRRIGATION 456
12.1. INTRODUCTION 456
12.2. SURFACE DRIP IRRIGATION OF PERMANENT CROPS 456
12.2.1. Introduction 456
12.2.2. Advantages and Disadvantages of Surface Drip Irrigation for Permanent Crops 456
12.2.3. Suitability 459
12.2.3.1. Suitable tree and vine crops 459
12.2.3.2. Geographical considerations 459
12.2.3.3. Water supply and quality 460
12.2.3.4. Maintenance and longevity 460
12.2.3.5. Irrigation uniformity 461
12.2.4. Surface Drip Design and Application 461
12.2.4.1. Drip emitters 461
12.2.4.1.1. Physical description of drip emitters 462
12.2.4.1.2. Emitter hydraulic characteristics 463
12.2.4.1.3. Coefficient of manufacturing variation 464
12.2.4.2. Lateral line drip tubing 465
12.2.4.2.1. Lateral line spacing 466
12.2.4.2.2. Lateral length 466
12.2.4.3. Emitter spacing 466
12.2.4.4. Design emission uniformity 467
12.2.4.5. Installation issues 471
12.2.5. Management, Evaluation, and Maintenance of Surface Drip Irrigation Systems 471
12.2.5.1. Water requirements 471
12.2.5.2. Crop response 472
12.2.5.3. Drip irrigation system application rate 472
12.2.5.4. Irrigation efficiency 472
12.2.5.5. Irrigation frequency 473
12.2.5.6. Special management issues 473
12.2.6. Evaluation of Surface Drip Irrigation Systems 474
12.3 SURFACE DRIP IRRIGATION FOR ROW CROPS 474
12.3.1. Advantages and Disadvantages of Surface Drip irrigation for Row Crops 474
12.3.2. Suitability 475
12.3.3. Drip Materials 476
12.3.4. Driplines 479
12.3.5. Manifolds 481
12.3.6. Emitter and Dripline Spacing 481
12.3.7. Installation and Extraction of Surface Driplines 481
12.3.8. Patterns of Soil Water Content 482
12.3.9. Patterns of Soil Salinity 484
12.3.10. Crop Response to Surface Drip Irrigation 486
12.3.10.1. Surface versus subsurface drip irrigation 486
12.3.10.2. Irrigation frequency effects 488
12.3.11. Managing a Drip Irrigation System of Row Crops 488
12.3.12. Using Plastic Mulch with Surface Drip Irrigation 491
LIST OF TERMS AND SYMBOLS 493
REFERENCES 493
CHAPTER 13. SUBSURFACE DRIP IRRIGATION 498
13.1. APPLICATION AND GENERAL SUITABILITY 498
13.1.1. Advantages of SDI 499
13.1.2. Disadvantages of SDI 501
13.1.3. Suitability Considerations 503
13.1.3.1. Suitable crops 503
13.1.3.2. Geographical and topographical considerations 503
13.1.3.3. Water supply and quality 504
13.1.3.4. Maintenance and longevity 505
13.1.3.5. System uniformity considerations 507
13.1.3.5.1. System uniformity considerations related to emitter clogging 508
13.1.3.5.2. System uniformity considerations related to root intrusion and root pinching 509
13.1.3.5.3. System uniformity considerations related to mechanical or pest damage 511
13.1.3.5.4. System uniformity considerations related to soil overburden and/or compaction 514
13.1.3.5.5. System uniformity considerations related to soil hydraulic parameters 515
13.1.3.5.6. System uniformity and longevity 516
13.2. SYSTEM DESIGN AND INSTALLATION 517
13.2.1. Materials and Components 517
13.2.1.1. Emitter and dripline characteristics 517
13.2.1.2. Additional SDI system components 518
13.2.2. Dripline and Manifold Design Issues 519
13.2.2.1. Dripline, crop row, and emitter spacing 519
13.2.2.2. Emitter flowrate 521
13.2.2.3. Dripline length 523
13.2.2.4. Flushing requirements and flushline design 527
13.2.2.4.1. Flushing velocity 527
13.2.2.4.2. Dripline inlet pressure and flowrate during flushing 528
13.2.2.4.3. Sizing the flushline and flush valve 529
13.2.2.5. Dripline depth 535
13.2.3. Installation Issues 539
13.2.4. Special or Unique Design Considerations 540
13.2.4.1. SDI design and electrical technologies 540
13.2.4.2. SDI design issues for recycled waters and biological effluent 541
13.2.4.3. Use of SDI in fully enclosed subirrigation (FES) systems 542
13.3. SOIL AND CROP MANAGEMENT 542
13.3.1. Soil Issues 542
13.3.1.1. Soil physical characteristics and soil water redistribution 542
13.3.1.2. Salinity aspects 546
13.3.1.3. Soil water redistribution problems caused by backpressure 549
13.3.1.4. Soil compaction 551
13.3.1.5. Managing the soil water budget components 551
13.3.1.6. Special or unique soil issues 552
13.3.1.6.1. Weed control 552
13.3.1.6.2. Application of insecticides for crop protection 553
13.3.1.6.3. Application of biological effluent 554
13.3.1.6.4. Soil profile injection of gases 555
13.3.2. Crop Issues 555
13.3.2.1. Crop water uptake and crop growth 555
13.3.2.2. Frequency of irrigation 556
13.3.2.3. Crop response to conjunctive water and nutrient management 557
13.4. SUMMARY 561
ACKNOWLEDGMENTS 562
LIST OF TERMS AND SYMBOLS 562
REFERENCES 564
CHAPTER 14. BUBBLER IRRIGATION 578
14.1. APPLICATION AND GENERAL SUITABILITY 578
14.1.1. Advantages and disadvantages 579
14.1.1.1. Potential advantages 579
14.1.1.2. Potential disadvantages 579
14.2. SYSTEM DESIGN AND APPLICATION 580
14.2.1. Materials and components 580
14.2.1.1. Gravity system emitters 581
14.2.1.2. Pressurized system emitters 581
14.2.1.3. Laterals and manifolds 585
14.2.1.4. System design procedures 588
14.3. SAMPLE DESIGN„LOW HEAD BUBBLER SYSTEM 588
14.4. MANAGEMENT, EVALUATION, AND MAINTENANCE 594
14.4.1. Soil Issues 594
14.4.2. Crops 595
14.4.3. Evaluation and Maintenance 595
LIST OF TERMS AND SYMBOLS 596
REFERENCES 598
CHAPTER 15. MICROSPRINKLER IRRIGATION 600
15.1. APPLICATION AND SUITABILITY OF MICROSPRINKLERS 600
15.1.1. Advantages of Microsprinkler Systems 601
15.1.2. Disadvantages of Microsprinkler Systems 601
15.2. MATERIALS AND COMPONENTS 602
15.2.1. Materials Used in Systems 602
15.2.1.1. Ferrous materials 603
15.2.1.2. Non-ferrous metals 603
15.2.1.3. Plastics 604
15.2.1.4. Elastomers 604
15.2.2. Microsprinkler Emitters 604
15.2.2.1. Emitter hydraulic characteristics 604
15.2.3. Emitter Manufacturing Variation 606
15.2.4. Emitter Types 606
15.2.4.1. Orifice control emitters 607
15.2.4.2. Vortex control emitters 607
15.2.4.3. Pressure compensating emitters 608
15.2.5. Emitter Wetting Patterns 610
15.2.6. Stake Assemblies 610
15.2.7. Lateral Tubing 615
15.3. LATERAL AND MANIFOLD DESIGN 616
15.3.1. Head Losses in Lateral Lines 617
15.3.2. Pressure Variation 617
15.3.3. Lateral Design 618
15.4. UNIQUE MANAGEMENT CONSIDERATIONS 625
15.4.1. Young Trees 625
15.4.2. Application Volumes 626
15.4.3. Freeze Protection 628
15.5. EVALUATION OF MICROSPRINKLER SYSTEMS 629
15.5.1. Uniformity 629
15.5.2. Irrigation System Efficiency 630
15.5.3. Wetting Pattern 630
15.5.4. Effects of Wear 631
LIST OF TERMS AND SYMBOLS 631
REFERENCES 632
INDEX 634