TABLE OF CONTENTS PREFACE...V CONTRIBUTORS... VI I. MICROIRRIGATION THEORY AND DESIGN PRINCIPLES CHAPTER 1. INTRODUCTION...1

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1 XI TABLE OF CONTENTS PREFACE...V CONTRIBUTORS... VI I. MICROIRRIGATION THEORY AND DESIGN PRINCIPLES CHAPTER 1. INTRODUCTION DEFINITION HISTORY AND CURRENT STATUS Early History Worldwide Early History in United States Current Irrigated Area Principal Crops Utilizing Microirrigation Trends Economics Expansion in Developing Countries GENERAL PRINCIPLES Advantages Increased water use efficiency Improved crop yields and quality Reduced nonbeneficial use Reduced deep percolation Use of saline water Improved fertilizer and other chemical application Decreased energy requirements Improved cultural practices Use of biological effluent and treated wastewaters Disadvantages Extensive maintenance requirements Salt accumulation near plants Restricted root development High system costs Restricted crop rotation System Considerations Design and installation considerations Maintenance considerations Management considerations Economic considerations... 15

2 XII System costs SYSTEM COMPONENTS Emission Devices Distribution System Control and Automation Filtration SYSTEM TYPES Surface Drip Irrigation Subsurface Drip Irrigation Bubbler Irrigation Microsprinkler Irrigation REFERENCES CHAPTER 2. SOIL WATER CONCEPTS INTRODUCTION Soil Water Regime for High Frequency Irrigation SOIL WATER Soil Water Content Soil Water Potential Soil Water Characteristic Curves Soil Water Measurements Gravimetric determination of soil water content Neutron scattering Time domain reflectometry (TDR) Tensiometers Heat dissipation Electrical resistance Capacitance SOIL WATER MOVEMENT Darcy s Law Alternative forms for Darcy s Law Richards Equation Measurements of Soil Hydraulic Parameters Direct measurements Indirect measurements Inverse methods Shortcuts with Pedotransfer Functions MODELING FOR EFFECTIVE MANAGEMENT AND DESIGN Simplified Hemispherical Model Quasi-Linear Solutions to Richards Equation... 39

3 Steady state solutions for point sources Steady state solutions for surface ponding Steady state solutions for line sources Transient (time-dependent) solutions Root Water Uptake Transient two and three-dimensional uptake functions Influence of Soil Spatial Variability on Soil Water Distribution ACKNOWLEDGMENTS LIST OF TERMS AND SYMBOLS REFERENCES CHAPTER 3. IRRIGATION SCHEDULING INTRODUCTION System Capacity System Uniformity Effects on Scheduling System Maintenance Effects on Scheduling Scheduling Constraints IRRIGATION SCHEDULING TECHNIQUES Water Balance (Evapotranspiration Base) Climatic factors affecting crop water use Crop factors affecting ET Soil factors affecting ET A direct ET approach Evaporation pans and atmometers Scheduling principles using evapotranspiration Soil Water Control Soil water measurement and controls Placement and implementation Plant Water Deficit Indicators Irrigation scheduling feedback loop using plant stress indicators Plant water potential measurements Plant size changes from plant-water stress Plant stress based on plant temperature Transpiration measurements by sap flow SUMMARY LIST OF TERMS AND SYMBOLS REFERENCES CHAPTER 4. SALINITY INTRODUCTION XIII

4 XIV 4.2. QUANTIFYING SALINITY AND SODICITY Salinity Sodicity CROP TOLERANCE Crop Salt Tolerance Factors Modifying Salt Tolerance Tolerance to Specific Solutes LEACHING Leaching Requirement Impact of Rainfall INFLUENCES OF IRRIGATION SYSTEM AND WATER SOURCE ON SOIL SALINITY Influence of Irrigation Method Reuse and Conjunctive Use of Waters Reuse Blending Cycling Environmental Consequences SALINITY MANAGEMENT PRACTICES Soil Salinity Distribution Crop Considerations Crop selection Other management techniques Infiltration Reclamation of Salt-Affected Soils Saline soils Sodic soils Boron leaching SUMMARY AND CONCLUSIONS REFERENCES CHAPTER 5. GENERAL SYSTEM DESIGN PRINCIPLES OVERVIEW OF THE DESIGN PROCESS Initial Assessment Microirrigation Layout and Components The Design Process SOURCES OF WATER Water Quantity and Quality Groundwater Surface Water

5 5.3. SYSTEM HYDRAULICS Hydraulic Principles Total head Pump energy requirements Total friction head Pipeline friction head loss Multiple outlet pipes Fitting, valve and component losses Emitter connection losses Emitter Hydraulics Microirrigation Lateral Lines Lateral line design procedures Manifolds Mainline Pipe System Design FILTRATION SUMMARY OF THE DESIGN PROCESS ACKNOWLEDGEMENTS LIST OF TERMS AND SYMBOLS REFERENCES SUPPLEMENTAL READING CHAPTER 6. ECONOMIC IMPLICATIONS OF MICROIRRIGATION INTRODUCTION The Farm-Level Perspective The Public Perspective FARM-LEVEL COSTS OF MICROIRRIGATION Fixed and Variable Costs Examples from the Literature Irrigating vegetables in Florida Irrigating field crops with subsurface drip irrigation systems Other examples FARM-LEVEL BENEFITS OF MICROIRRIGATION Crop Yield Effects Deciduous fruits and nuts Citrus Small fruits Tomato Melons XV

6 XVI Other fruits and vegetables Cotton Sugarcane and sugarbeets Frost and Freeze Protection with Microsprinklers Fertigation Chemical Application of Non-Fertilizer Materials Irrigation with Saline Water and Effluent FARM-LEVEL OBSERVATIONS PUBLIC BENEFITS AND POLICY IMPLICATIONS SUMMARY ACKNOWLEDGEMENTS REFERENCES II. OPERATION AND MAINTENANCE PRINCIPLES CHAPTER 7. AUTOMATION INTRODUCTION CONTROL THEORY Control Methods On-off control Stepwise control Continuous control Linear Systems AUTOMATIC CONTROL SYSTEMS Soil Water Methods Soil water potential Soil water content Wetting front detection Plant Water Methods Leaf water potential method Plant canopy temperature method Plant turgor methods Evapotranspiration estimates Evapotranspiration models Direct measurement of Et c INSTRUMENTATION AND HARDWARE Controllers Valves Flowmeters

7 XVII Environmental Sensors Filters Chemical Injectors SUMMARY REFERENCES CHAPTER 8. APPLICATION OF CHEMICAL MATERIALS INTRODUCTION Definitions Basic Information Advantages of Chemigation Disadvantages of Chemigation Types of Agrochemicals Water soluble chemicals Wettable powders Emulsifiable (oil soluble) chemicals Gases Safety Following the label and other regulations General Considerations Problems with chemical mixes CHEMICAL INJECTION METHODS Injection Pumps and Systems Pollution Prevention Electrical and mechanical interlock system Backflow prevention in the irrigation line Injection line components Chemical Supply Tanks and Secondary Containment Corrosion Resistance of Surfaces Maintenance CHEMICALS AND CALCULATION OF INJECTION RATES Fertigation Calculation of plant nutrient requirements Fertilizer selection and calculation of injection rates Chemigation of Non-Fertilizer Materials REFERENCES CHAPTER 9. APPLICATION OF BIOLOGICAL EFFLUENT INTRODUCTION Advantages of Applying Biological Effluent

8 XVIII Disadvantages of Applying Biological Effluent CHARACTERISTICS OF BIOLOGICAL EFFLUENTS Effluent Source and Degree of Treatment Composition of Effluent Characteristics of Effluents Used in Some Microirrigation Studies BIOLOGICAL EFFLUENT CONSTITUENT BEHAVIOR IN SOILS Nitrogen Uptake by Plants and Potential Loss Mechanisms Phosphorus Uptake by Plants and Potential Loss Mechanisms Trace Element Uptake by Plants and Potential Loss Mechanisms Salinity Management Pathogenic Organisms HEALTH CONSIDERATIONS Typical Regulations Practices to Meet the Regulations SITE CONSIDERATIONS Soils Climate Crops Land Area DESIGN AND MANAGEMENT CONSIDERATIONS System Components Filtration Requirements Chemical Treatment Requirements Dripline Flushing Monitoring Procedures ACKNOWLEDGEMENTS REFERENCES CHAPTER 10. FIELD PERFORMANCE AND EVALUATION INTRODUCTION Uniformity of Water Application Order of Significance of Design Parameters The Goal of Microirrigation Application VARIATIONS OF IRRIGATION APPLICATION Variations from Hydraulic Design Manufacturer s Variation Effects by Grouping of Emitters Possible Clogging Effects Total Variation

9 10.3. UNIFORMITY CONSIDERATIONS Uniformity Parameters A Linearized Water Application Function Uniformity and Total Yield Uniformity and Total Economic Return FIELD PERFORMANCE AND IRRIGATION STRATEGY Significance of Irrigation Scheduling Optimal Irrigation Conventional Irrigation A Simple Irrigation Schedule Irrigation Strategy for Environmental Protection Microirrigation for Water Conservation Comparing optimal schedule with conventional irrigation schedule Comparing simple irrigation schedule with conventional irrigation schedule Comparing simple irrigation schedule with the optimal irrigation schedule Comparing the irrigation schedule for environmental protection with the optimal irrigation schedule Comparing the irrigation schedule for environmental protection with the simple irrigation schedule FIELD EVALUATION AND ADJUSTMENT Design Criteria of Microirrigation Uniformity parameters Determination of design criteria Selection of design criteria Field Evaluation Significance of field evaluation Uniformity measurement Repairs and Adjustment Repairing leaks in the system Adjustment of irrigation time Adjustments for changes in uniformity LIST OF TERMS AND SYMBOLS REFERENCES CHAPTER 11. MAINTENANCE EMITTER OPERATION Evaluation of Emitter Clogging Source of water Surface water Groundwater XIX

10 XX Wastewater Water Quality Physical aspects Chemical aspects Biological aspects Causes Physical, chemical, and biological factors Microorganisms Macroorganisms WATER TREATMENT Filtration Screen filters Disk filters Media filters Settling basins Cyclonic filters or centrifugal separators Filter design and operation Chemical Treatment Chemical precipitation Acid treatment Chlorination Chemical injection MAINTENANCE OPERATION Approach Chemical water treatment research Preventive maintenance practices Flushing Reclamation GUIDELINE AND PRACTICES REFERENCES SUPPLEMENTAL READING III. SYSTEM TYPE AND MANAGEMENT PRINCIPLES CHAPTER 12. SURFACE DRIP IRRIGATION INTRODUCTION SURFACE DRIP IRRIGATION OF PERMANENT CROPS Introduction Advantages and Disadvantages of Surface Drip Irrigation for Permanent Crops

11 Suitability Suitable tree and vine crops Geographical considerations Water supply and quality Maintenance and longevity Irrigation uniformity Surface Drip Design and Application Drip emitters Physical description of drip emitters Emitter hydraulic characteristics Coefficient of manufacturing variation Lateral line drip tubing Lateral line spacing Lateral length Emitter spacing Design emission uniformity Installation issues Management, Evaluation, and Maintenance of Surface Drip Irrigation Systems Water requirements Crop response Drip irrigation system application rate Irrigation efficiency Irrigation frequency Special management issues Evaluation of Surface Drip Irrigation Systems SURFACE DRIP IRRIGATION FOR ROW CROPS Advantages and Disadvantages of Surface Drip irrigation for Row Crops Suitability Drip Materials Driplines Manifolds Emitter and Dripline Spacing Installation and Extraction of Surface Driplines Patterns of Soil Water Content Patterns of Soil Salinity Crop Response to Surface Drip Irrigation Surface versus subsurface drip irrigation Irrigation frequency effects Managing a Drip Irrigation System of Row Crops Using Plastic Mulch with Surface Drip Irrigation LIST OF TERMS AND SYMBOLS XXI

12 XXII REFERENCES CHAPTER 13. SUBSURFACE DRIP IRRIGATION APPLICATION AND GENERAL SUITABILITY Advantages of SDI Disadvantages of SDI Suitability Considerations Suitable crops Geographical and topographical considerations Water supply and quality Maintenance and longevity System uniformity considerations System uniformity considerations related to emitter clogging System uniformity considerations related to root intrusion and root pinching System uniformity considerations related to mechanical or pest damage System uniformity considerations related to soil overburden and/or compaction System uniformity considerations related to soil hydraulic parameters System uniformity and longevity SYSTEM DESIGN AND INSTALLATION Materials and Components Emitter and dripline characteristics Additional SDI system components Dripline and Manifold Design Issues Dripline, crop row, and emitter spacing Emitter flowrate Dripline length Flushing requirements and flushline design Flushing velocity Dripline inlet pressure and flowrate during flushing Sizing the flushline and flush valve Dripline depth Installation Issues Special or Unique Design Considerations SDI design and electrical technologies SDI design issues for recycled waters and biological effluent Use of SDI in fully enclosed subirrigation (FES) systems SOIL AND CROP MANAGEMENT Soil Issues Soil physical characteristics and soil water redistribution

13 XXIII Salinity aspects Soil water redistribution problems caused by backpressure Soil compaction Managing the soil water budget components Special or unique soil issues Weed control Application of insecticides for crop protection Application of biological effluent Soil profile injection of gases Crop Issues Crop water uptake and crop growth Frequency of irrigation Crop response to conjunctive water and nutrient management SUMMARY ACKNOWLEDGMENTS LIST OF TERMS AND SYMBOLS REFERENCES CHAPTER 14. BUBBLER IRRIGATION APPLICATION AND GENERAL SUITABILITY Advantages and disadvantages Potential advantages Potential disadvantages SYSTEM DESIGN AND APPLICATION Materials and components Gravity system emitters Pressurized system emitters Laterals and manifolds System design procedures SAMPLE DESIGN LOW HEAD BUBBLER SYSTEM MANAGEMENT, EVALUATION, AND MAINTENANCE Soil Issues Crops Evaluation and Maintenance LIST OF TERMS AND SYMBOLS REFERENCES CHAPTER 15. MICROSPRINKLER IRRIGATION APPLICATION AND SUITABILITY OF MICROSPRINKLERS

14 XXIV Advantages of Microsprinkler Systems Disadvantages of Microsprinkler Systems MATERIALS AND COMPONENTS Materials Used in Systems Ferrous materials Non-ferrous metals Plastics Elastomers Microsprinkler Emitters Emitter hydraulic characteristics Emitter Manufacturing Variation Emitter Types Orifice control emitters Vortex control emitters Pressure compensating emitters Emitter Wetting Patterns Stake Assemblies Lateral Tubing LATERAL AND MANIFOLD DESIGN Head Losses in Lateral Lines Pressure Variation Lateral Design UNIQUE MANAGEMENT CONSIDERATIONS Young Trees Application Volumes Freeze Protection EVALUATION OF MICROSPRINKLER SYSTEMS Uniformity Irrigation System Efficiency Wetting Pattern Effects of Wear LIST OF TERMS AND SYMBOLS REFERENCES INDEX...609