PRINCIPLESOF SOIL AND PLANTWATER RELATIONS

M.B. KIRKHAMKansas State University

ELSEVIERACADEMIC

PRESS

AMSTERDAM • BOSTON • HEIDELBERG • LONDONNEW YORK • OXFORD • PARIS • SAN DIEGO

SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO

Contents

Preface xv

1 Introduction 1I. Why Study Soil-Plant-Water Relations? 1

II. Plant Growth Curves 6III. Appendix: Biography of John Napier 11

2 Definitions of Physical Units and theInternational System 15

I. Definitions 15II. Le Systeme International d'Unites 20

III. Example: Applying Units of Work and Pressureto a Root 23

IV. Appendix: Biography of Isaac Newton 24

3 Structure and Properties of Water 27I. Structure of Water 27

II. Forces That Bind Water Molecules Together 28III. Properties of Water 30IV. Appendix: Biography of Johannes van der Waals 39

viii CONTENTS

4 Tensiometers 41I. Description of a Tensiometer 41

II. Types of Tensiometers 45III. Temperature Effects on Tensiometers 50IV. Applications of Tensiometers 51V. Appendix: Biography of L.A. Richards 52

5 Soil-Water Terminology and Applications 55I. Water Content 55

II. Water Potential 55III. Heads in a Column of Soil 60IV. Movement of Water Between Tensiometers 63V. Appendix: Biography of William L. Powers 64

6 Static Water in Soil 67I. Surface Tension 67

II. Examples of Surface Tension 73III. Rise and Fall of Water in Soil Pores 75IV. Appendix: History of Surface Tension 79V. Appendix: Biography of Marquis de Laplace 82

7 Water Movement in Saturated Soil 85I. Darcy'sLaw 85

II. Hydraulic Conductivity 87III. Laplace's Equation 88IV. Ellipse Equation 88V. Linear Flow Laws 93

VI. Appendix: Biography of Apollonius of Perga 96VII. Appendix: Biography of Henry Darcy 97

8 Field Capacity, Wilting Point, Available Water, and theNon-Limiting Water Range 101

I. Field Capacity 101II. Wilting Point 104

III. Available Water 107IV. Non-Limiting Water Range 108V. Biographies of Briggs and Shantz 110

9 Penetrometer Measurements 117I. Definition, Types of Penetrometers, and Uses 117

II. Types of Tests 118

CONTENTS IX

III. What Penetrometer Measurements Depend Upon 119IV. Cone Penetrometer 121V. Appendix: Biography of Champ Tanner 124

I 0 Measurement of Oxygen Diffusion Rate 129I. The Oxygen Diffusion Rate Method 129

II. Electrolysis 131III. Model and Principles of the ODR Method 134IV. Method 137V. Appendix: Biography of Michael Faraday 141

II Infiltration 145I. Definition of Infiltration 145

II. Four Models of One-Dimensional Infiltration 147III. Two- and Three-Dimensional Infiltration 150IV. Redistribution 150V. Tension Infiltrometer or Disc Permeameter 151

VI. Minidisk Infiltrometer 154VII. Measurement of Unsaturated Hydraulic Conductivity

and Sorptivity with the Tension Infiltrometer 155VIII. Measurement of Repellency with the Tension Infiltrometer 160

IX. Measurement of Mobility with the Tension Infiltrometer 161X. Ellipsoidal Description of Water Flow into Soil from

a Surface Disc 166XI. Appendix: Biography of John Philip 168

1 2 Pore Volume 173I. Definitions 173

II. Illustration of Breakthrough Curves and Pore Volumes 175HI. Mathematical Analysis of Pore Volume 175IV. Calculation of a Pore Volume 179V. Pore Volumes Based on Length Units 181

VI. Miscible Displacement 183VII. Relation Between Mobile Water Content and

Pore Volume 183VIII. Appendix: Biography of Donald Nielsen 183

1 3 Time Domain Reflectometry to Measure VolumetricSoil Water Content 187

I. Definitions 187II. Dielectric Constant, Frequency Domain, and

Time Domain 189

X CONTENTS

III. Theory for Use of the Dielectric Constant to Measure SoilWater Content 190

IV. Coaxial Cable and Waveguides 194V. Measurement of Soil Water Content Using TDR 195

VI. Practical Information When Using TDR to MeasureSoil Water Content 197

VII. Example of Using TDR to Determine Root Water Uptake 199VIII. HydroSense™ 199

IX. Appendix: Biography of Heinrich Hertz 201X. Appendix: Biography of Sergei Schelkunoff 202

1 4 Root Anatomy and Poiseuille's Law for WaterFlow in Roots 207

I. Root Anatomy 207II. Poiseuille's Law 216

III. Assumptions of Poiseuille's Law 217IV. Calculations of Flow Based on Poiseuille's Law 2I8V. Agronomic Applications of Poiseuille's Law 222

VI. Appendix: Biography of J.L.M. Poiseuille 225VII. Appendix: Biography of Osborne Reynolds 225

1 5 Gardner's Equation for Water Movement toPlant Roots 229

I. Description ot the Equation 229II. Assumptions 231

III. Values for the Rate of Water Uptake 23 1IV. Examples 233V. Effect of Wet and Dry Soil 233

VI. Effect of Root Radius 234VII. Comparison of Matric Potential at Root and in

Soil for Different Rates of Water Uptake 235VIII. Effect of Root Distribution on Wilting 236

IX. Final Comment 237X. Appendix: Biography of Wilford Gardner 237

1 6 Measurement of Water Potential with ThermocouplePsychrometers 241

I. Relation Between Water Potential and RelativeHumidity 241

II. Thermoelectric Effects 242III. Joule Heating 244IV. Thermoelectric Power 245

CONTENTS XI

V. Relationship Between Vapor Pressure and Temperature 246VI. Calibration 247

VII. Importance of Isothermal Conditions When MakingMeasurements 248

VIII. Types of Thermocouple Psychrometers 249IX. Appendix: Biography of J.C.A. Peltier 257X. Appendix: Biography of James Prescott Joule 257

XL Appendix: Biography of William Thomson,Baron Kelvin 258

1 7 Measurement of Water Potential with PressureChambers 263

I. Comparison of Measurements Made With the PressureChamber and the Thermocouple Psychrometer 263

II. Advantages and Disadvantages of the Pressure Chamber 268III. Hydraulic Press 271IV. Pump-Up Pressure Chamber 274V. Appendix: Biography of Per Scholander 274

VI. Appendix: Biography of John Boyer 276

1 8 Stem Anatomy and Measurement of OsmoticPotential and Turgor Potential UsingPressure-Volume Curves 281

I. Stem Anatomy 281II. Measurement of the Components of the Water Potential 287

III. Osmotic Potential (v|/s) 289IV. Theory of Scholander Pressure-Volume Curves 289V How to Analyze a Pressure-Volume Curve 295

VI. Turgor Potential (\|/p) 298VII. Measurement of Plant Water Content and

Relative Water Content 300VIII. Osmometer 305

IX. Appendix: Biography of Wilhelm Pfeffer 308X. Appendix: Biography of Jacobus van't Hoff 310

XL Appendix: Biography of Rudolf Clausius 311

1 9 The Ascent of Water in Plants 315I. The Problem 315

II. How Water Gets to the Top of Tall Buildingsand Animals 316

III. Cohesion Theory 317IV. Limitations of the Cohesion Theory 319

xii CONTENTS

V. Alternative Theory to the Cohesion Theory 327VI. New Techniques to Confirm the Cohesion Theory 331

VII. Controvery About the Cohesion Theory 332VIII. Potentials in the Soil-Plant-Atmosphere Continuum 332

IX. Appendix: Biography of Henry Dixon 335X. Appendix: Biography of John Joly 336

20 Electrical Analogues for Water Movement throughthe Soil-Plant-Atmosphere Continuum 341

I. The Analogy 341II. Measurement of Resistance With the Wheatstone Bridge 342

III. Law of Resistance 343IV. Units of Electrical Conductivity 345V. Example of an Electrical Analogue Applied to Soil With

Wormholes 346VI. Van den Honert's Equation 347

VII. Proof of van den Honert's Equation 349VIII. Appendix: Biography of Georg Ohm 350

IX. Appendix: Biography of Charles Wheatstone 352X. Appendix: Biographies of Members of the Siemens Family 353

2 1 Leaf Anatomy and Leaf Elasticity 357I. Leaf Anatomy 357

II. Internal Water Relations 363III. Elasticity 366IV. Elasticity Applied to Plant Leaves 369V. Appendix: Biography of Robert Hooke 374

VI. Appendix: Biography of Thomas Young 375

22 Stomata and Measurement of Stomatal Resistance 379I. Definition of Stomata and Their Distribution 379

II. Stomatal Anatomy of Dicots and Monocots 380III. Stomatal Density 381IV. Diffusion of Gases Through Stomatal Pores 383V. Guard Cells 384

VI. Mechanism of Stomatal Opening 386VII. Boundary Layer 387

VIII. Leaf Resistances 388IX. Measurement of Stomatal Aperture and Stomatal

Resistance 392X. Theory of Mass-Flow and Diffusion Porometers 395

XI. Appendix: Biography of Adolf Fick 397

CONTENTS XIII

23 Solar Radiation, Black Bodies, Heat Budget, andRadiation Balance 403

I. Solar Radiation 403II. Terrestrial Radiation 404

III. Definition of a Black Body 406IV. Example of a Black Body 408V. Temperature of a Black Body 409

VI. Gray Body 410VII. Spectrum of a Black Body 410

VIII. Sun's Temperature 412IX. Earth's Temperature 413X. Comparison of Solar and Terrestrial Radiation 413

XI. Heat Budget 414XII. Radiation Balance 416

XIII. Appendix: Biography of Gustav Kirchhoff 418XIV. Appendix: Biography of Josef Stefan 420XV. Appendix: Biography of Ludwig Boltzmann 421

XVI. Appendix: Biography of Wilhelm Wien 422

24 Measurement of Canopy Temperature with InfraredThermometers 425

I. Infrared Thermometers 426II. Definitions 427

III. Principles of Infrared Thermometry 427IV. Use of a Portable Infrared Thermometer 430V. Calibration of Infrared Thermometers 431

VI. Advantages of Infrared Thermometers 432VII. Appendix: Biography of Ray Jackson 433

25 Stress-Degree-Day Concept and Crop-Water-StressIndex 437

I. Stress-Degree-Day Procedure 437II. Canopy-Minus-Air Temperature and

Evapotranspiration 440HI. Crop-Water-Stress Index 443IV. How to Calculate the Crop-Water-Stress Index 448V. Crop-Water-Stress Index for Alfalfa, Soybeans,

and Cotton 448VI. Importance of a Wide Range of Vapor-Pressure

Deficit Values 451VII. Appendix: Biography of Sherwood Idso 451

Xiv CONTENTS

26 Potential Evapotranspiration 455I. Definition of Potential Evapotranspiration 455

II. Factors That Affect Potential Evapotranspiration 455III. Advection 464IV. Example Calculation to Determine Potential

Evapotranspiration 464V. Appendix: Biography of Howard Penman 466

27 Water and Yield 469I. De Wit's Analysis 469

II. Relationship Between Yield and Transpiration andYield and Evapotranspiration 471

III. Water and Marketable Yield 478IV. Water and Quality 478V. Crop-Water-Use Efficiency 479

VI. Appendix: Biography of Cornelius de Wit 482

Index 485