Principles of soil and plant water relations

1 Introduction 1 I. Why Study Soil-Plant-Water Relations? 1 II. Plant Growth Curves 6 III. Appendix: Biography of John Napier 11 2 Definitions of Physical Units and the International System 15 I.Definitions 15 II. Le Système International d’Unités 20 III. Example: Applying Units of Work and Pressure to a Root 23 IV. Appendix: Biography of Isaac Newton 24 3 Structure and Properties of Water 27 I. Structure of Water 27 II. Forces That Bind Water Molecules Together 28 III. Properties of Water 30 IV. Appendix: Biography of Johannes van der Waals 39 viii CONTENTS 4 Tensiometers 41 I. Description of a Tensiometer 41 II. Types of Tensiometers 45 III. Temperature Effects on Tensiometers 50 IV. Applications of Tensiometers 51 V. Appendix: Biography of L.A. Richards 52 5 Soil-Water Terminology and Applications 55 I. Water Content 55 II. Water Potential 55 III. Heads in a Column of Soil 60 IV. Movement of Water Between Tensiometers 63 V. Appendix: Biography of William L. Powers 64 6 Static Water in Soil 67 I. Surface Tension 67 II. Examples of Surface Tension 73 III. Rise and Fall of Water in Soil Pores 75 IV. Appendix: History of Surface Tension 79 V. Appendix: Biography of Marquis de Laplace 82 7 Water Movement in Saturated Soil 85 I. Darcy’s Law 85 II. Hydraulic Conductivity 87 III. Laplace’s Equation 88 IV. Ellipse Equation 88 V. Linear Flow Laws 93 VI. Appendix: Biography of Apollonius of Perga 96 VII. Appendix: Biography of Henry Darcy 97 8 Field Capacity, Wilting Point, Available Water, and the Non-Limiting Water Range 101 I. Field Capacity 101 II. Wilting Point 104 III. Available Water 107 IV. Non-Limiting Water Range 108 V. Biographies of Briggs and Shantz 110 9 Penetrometer Measurements 117 I. Definition, Types of Penetrometers, and Uses 117 II. Types of Tests 118 III. What Penetrometer Measurements Depend Upon 119 IV. Cone Penetrometer 121 V. Appendix: Biography of Champ Tanner 124 10 Measurement of Oxygen Diffusion Rate 129 I. The Oxygen Diffusion Rate Method 129 II. Electrolysis 131 III. Model and Principles of the ODR Method 134 IV.Method 137 V. Appendix: Biography of Michael Faraday 141 11 Infiltration 145 I. Definition of Infiltration 145 II. Four Models of One-Dimensional Infiltration 147 III. Two- and Three-Dimensional Infiltration 150 IV. Redistribution 150 V. Tension Infiltrometer or Disc Permeameter 151 VI. Minidisk Infiltrometer 154 VII. Measurement of Unsaturated Hydraulic Conductivity and Sorptivity with the Tension Infiltrometer 155 VIII. Measurement of Repellency with the Tension Infiltrometer 160 IX. Measurement of Mobility with the Tension Infiltrometer 161 X. Ellipsoidal Description of Water Flow into Soil from a Surface Disc 166 XI. Appendix: Biography of John Philip 168 12 Pore Volume 173 I. Definitions 173 II. Illustration of Breakthrough Curves and Pore Volumes 175 III. Mathematical Analysis of Pore Volume 175 IV. Calculation of a Pore Volume 179 V. Pore Volumes Based on Length Units 181 VI. Miscible Displacement 183 VII. Relation Between Mobile Water Content and Pore Volume 183 VIII. Appendix: Biography of Donald Nielsen 183 13 Time Domain Reflectometry to Measure Volumetric SoilWater Content 187 I. Definitions 187 II. Dielectric Constant, Frequency Domain, and Time Domain 189 CONTENTS ix x CONTENTS III. Theory for Use of the Dielectric Constant to Measure Soil Water Content 190 IV. Coaxial Cable and Waveguides 194 V. Measurement of Soil Water Content Using TDR 195 VI. Practical Information When Using TDR to Measure Soil Water Content 197 VII. Example of Using TDR to Determine Root Water Uptake 199 VIII. HydroSense™ 199 IX. Appendix: Biography of Heinrich Hertz 201 X. Appendix: Biography of Sergei Schelkunoff 202 14 Root Anatomy and Poiseuille’s Law for Water Flow in Roots 207 I. Root Anatomy 207 II. Poiseuille’s Law 216 III. Assumptions of Poiseuille’s Law 217 IV. Calculations of Flow Based on Poiseuille’s Law 218 V. Agronomic Applications of Poiseuille’s Law 222 VI. Appendix: Biography of J.L.M. Poiseuille 225 VII. Appendix: Biography of Osborne Reynolds 225 15 Gardner’s Equation for Water Movement to Plant Roots 229 I. Description of the Equation 229 II. Assumptions 231 III. Values for the Rate of Water Uptake 231 IV. Examples 233 V. Effect of Wet and Dry Soil 233 VI. Effect of Root Radius 234 VII. Comparison of Matric Potential at Root and in Soil for Different Rates of Water Uptake 235 VIII. Effect of Root Distribution on Wilting 236 IX. Final Comment 237 X. Appendix: Biography of Wilford Gardner 237 16 Measurement of Water Potential with Thermocouple Psychrometers 241 I. Relation Between Water Potential and Relative Humidity 241 II. Thermoelectric Effects 242 III. Joule Heating 244 IV. Thermoelectric Power 245 CONTENTS xi V. Relationship Between Vapor Pressure and Temperature 246 VI. Calibration 247 VII. Importance of Isothermal Conditions When Making Measurements 248 VIII. Types of Thermocouple Psychrometers 249 IX. Appendix: Biography of J.C.A. Peltier 257 X. Appendix: Biography of James Prescott Joule 257 XI. Appendix: Biography of William Thomson, Baron Kelvin 258 17 Measurement of Water Potential with Pressure Chambers 263 I. Comparison of Measurements Made With the Pressure Chamber and the Thermocouple Psychrometer 263 II. Advantages and Disadvantages of the Pressure Chamber 268 III. Hydraulic Press 271 IV. Pump-Up Pressure Chamber 274 V. Appendix: Biography of Per Scholander 274 VI. Appendix: Biography of John Boyer 276 18 Stem Anatomy and Measurement of Osmotic Potential and Turgor Potential Using Pressure-Volume Curves 281 I. Stem Anatomy 281 II. Measurement of the Components of the Water Potential 287 III. Osmotic Potential (ψS) 289 IV. Theory of Scholander Pressure-Volume Curves 289 V How to Analyze a Pressure-Volume Curve 295 VI. Turgor Potential (ψP) 298 VII. Measurement of Plant Water Content and Relative Water Content 300 VIII.Osmometer 305 IX. Appendix: Biography of Wilhelm Pfeffer 308 X. Appendix: Biography of Jacobus van’t Hoff 310 XI. Appendix: Biography of Rudolf Clausius 311 19 The Ascent of Water in Plants 315 I. The Problem 315 II. How Water Gets to the Top of Tall Buildings and Animals 316 III. Cohesion Theory 317 IV. Limitations of the Cohesion Theory 319 V. Alternative Theory to the Cohesion Theory 327 VI. New Techniques to Confirm the Cohesion Theory 331 VII. Controvery About the Cohesion Theory 332 VIII. Potentials in the Soil-Plant-Atmosphere Continuum 332 IX. Appendix: Biography of Henry Dixon 335 X. Appendix: Biography of John Joly 336 20 Electrical Analogues for Water Movement through the Soil-Plant-Atmosphere Continuum 341 I. The Analogy 341 II. Measurement of Resistance With the Wheatstone Bridge 342 III. Law of Resistance 343 IV. Units of Electrical Conductivity 345 V. Example of an Electrical Analogue Applied to Soil With Wormholes 346 VI. Van den Honert’s Equation 347 VII. Proof of van den Honert’s Equation 349 VIII. Appendix: Biography of Georg Ohm 350 IX. Appendix: Biography of Charles Wheatstone 352 X. Appendix: Biographies of Members of the Siemens Family 353 21 Leaf Anatomy and Leaf Elasticity 357 I. Leaf Anatomy 357 II. Internal Water Relations 363 III. Elasticity 366 IV. Elasticity Applied to Plant Leaves 369 V. Appendix: Biography of Robert Hooke 374 VI. Appendix: Biography of Thomas Young 375 22 Stomata and Measurement of Stomatal Resistance 379 I. Definition of Stomata and Their Distribution 379 II. Stomatal Anatomy of Dicots and Monocots 380 III. Stomatal Density 381 IV. Diffusion of Gases Through Stomatal Pores 383 V. Guard Cells 384 VI. Mechanism of Stomatal Opening 386 VII. Boundary Layer 387 VIII. Leaf Resistances 388 IX. Measurement of Stomatal Aperture and Stomatal Resistance 392 X. Theory of Mass-Flow and Diffusion Porometers 395 XI. Appendix: Biography of Adolf Fick 397 xii CONTENTS 23 Solar Radiation, Black Bodies, Heat Budget, and RadiationBalance 403 I. Solar Radiation 403 II. Terrestrial Radiation 404 III. Definition of a Black Body 406 IV. Example of a Black Body 408 V. Temperature of a Black Body 409 VI. Gray Body 410 VII. Spectrum of a Black Body 410 VIII. Sun’s Temperature 412 IX. Earth’s Temperature 413 X. Comparison of Solar and Terrestrial Radiation 413 XI. Heat Budget 414 XII. Radiation Balance 416 XIII. Appendix: Biography of Gustav Kirchhoff 418 XIV. Appendix: Biography of Josef Stefan 420 XV. Appendix: Biography of Ludwig Boltzmann 421 XVI. Appendix: Biography of Wilhelm Wien 422 24 Measurement of Canopy Temperature with Infrared Thermometers 425 I. Infrared Thermometers 426 II. Definitions 427 III. Principles of Infrared Thermometry 427 IV. Use of a Portable Infrared Thermometer 430 V. Calibration of Infrared Thermometers 431 VI. Advantages of Infrared Thermometers 432 VII. Appendix: Biography of Ray Jackson 433 25 Stress-Degree-Day Concept and Crop-Water-Stress Index 437 I. Stress-Degree-Day Procedure 437 II. Canopy-Minus-Air Temperature and Evapotranspiration 440 III. Crop-Water-Stress Index 443 IV. How to Calculate the Crop-Water-Stress Index 448 V. Crop-Water-Stress Index for Alfalfa, Soybeans, and Cotton 448 VI. Importance of a Wide Range of Vapor-Pressure Deficit Values 451 VII. Appendix: Biography of Sherwood Idso 451 CONTENTS xiii 26 Potential Evapotranspiration 455 I. Definition of Potential Evapotranspiration 455 II. Factors That Affect Potential Evapotranspiration 455 III.Advection 464 IV. Example Calculation to Determine Potential Evapotranspiration 464 V. Appendix: Biography of Howard Penman 466 27 Water and Yield 469 I. De Wit’s Analysis 469 II. Relationship Between Yield and Transpiration and Yield and Evapotranspiration 471 III. Water and Marketable Yield 478 IV. Water and Quality 478 V. Crop-Water-Use Efficiency 479 VI. Appendix: Biography of Cornelius de Wit 482 Index