Principles of Soil and Plant Water Relations

1. Introduction　

1.1. Why Study Soil–Plant–Water Relations?　

1.2. Plant Growth Curves　

1.3. Appendix: Biography of John Napier　

2. Definitions of Physical Units and the International System　

2.1. Definitions　

2.2. Le Système International d'unités　

2.3. Example: Applying Units of Work and Pressure to a Root　

2.4. Appendix: Biography of Isaac Newton　

3. Structure and Properties of Water　

3.1. Structure of Water　

3.2. Forces that Bind Water Molecules Together　

3.3. Properties of Water　

3.4. Appendix: Biography of Johannes van der Waals　

4. Soil–Water Terminology and Applications　

4.1. Water Content　

4.2. Water Potential　

4.3. Heads in a Column of Soil　

4.4. Movement of Water between Tensiometers　

4.5. Appendix: Biography of William L. Powers　

5. Tensiometers　

5.1. Description of a Tensiometer　

5.2. Types of Tensiometers　

5.3. Temperature Effects on Tensiometers　

5.4. Applications of Tensiometers　

5.5. Appendix: Biography of L.A. Richards　

6. Static Water in Soil　

6.1. Surface Tension　

6.2. Examples of Surface Tension　

6.3. Rise and Fall of Water in Soil Pores　

6.4. Appendix: Biography of Marquis de Laplace　

7. Water Movement in Saturated Soil　

7.1. Darcy's Law　

7.2. Hydraulic Conductivity　

7.3. Laplace's Equation　

7.4. Ellipse Equation　

7.5. Linear Flow Laws　

7.6. Appendix: Biography of Apollonius of Perga　

7.7. Appendix: Biography of Henry Darcy

8. Time Domain Reflectometry

8.1. Definitions　

8.2. Dielectric Constant, Frequency Domain, and Time Domain　

8.3. Theory for the Use of the Dielectric Constant to Measure Soil Water Content　

8.4. Coaxial Cable and Waveguides　

8.5. Measurement of Soil Water Content Using TDR　

8.6. Practical Information When Using TDR to Measure Soil Water Content　

8.7. Example of Using TDR to Determine Root Water Uptake　

8.8. Commercially Available Equipment　

8.9. Appendix: Biography of Heinrich Hertz　

8.10. Appendix: Biography of Sergei　Schelkunoff　

9. Dual Thermal Probes　

9.1. Introduction　

9.2. Thermal Properties of Soils　

9.3. Theory of the Dual-Probe Heat-Pulse Method　

9.4. Example Calculation　

9.5. Meaning of Q　

9.6. Measurements of Differences of Water Content

9.7. Errors

9.8. Advantages　

9.9. Calibration　

9.10. Measurements Near the Soil Surface　

9.11. Convection and Its Effect on Measurements　

9.12. Measurement of Electrical Conductivity　

9.13. Determination of Soil Water Movement　

9.14. Measurements with Roots in Soil　

9.15. Hydraulic Lift　

9.16. Commercially Available Equipment　

9.17. Summary　

9.18. Appendix: Biography of John Jaeger

10. Field Capacity, Wilting Point, Available Water, and the Nonlimiting Water Range　

10.1. Field Capacity　

10.2. Wilting Point　

10.3. Available Water　

10.4. Nonlimiting Water Range　

10.5. Biographies of Briggs and Shantz　

11. Penetrometers　

11.1. Definition, Types of Penetrometers, and Uses　

11.2. Types of Tests　

11.3. What Penetrometer Measurements Depend upon　

11.4. Cone Penetrometer　

11.5. Appendix: Biography of Champ Tanner

12. Oxygen Diffusion Rate　

12.1. The Oxygen Diffusion Rate Method　

12.2. Electrolysis　

12.3. Model and Principles of the ODR Method　

12.4. Method　

12.5. Appendix: Biography of Michael Faraday　

13. Infiltration　

13.1. Definition of Infiltration　

13.2. Four Models of One-Dimensional Infiltration　

13.3. Two- and Three-Dimensional Infiltration　

13.4. Redistribution　

13.5. Tension Infiltrometer or Disc Permeameter　

13.6. Minidisk Infiltrometer　

13.7. Measurement of Unsaturated Hydraulic Conductivity and Sorptivity with the Tension Infiltrometer　

13.8. Measurement of Repellency with the Tension Infiltrometer　

13.9. Measurement of Mobility with the Tension Infiltrometer　

13.10. Ellipsoidal Description of Water Flow into Soil from a Surface Disc　

13.11. Appendix: Biography of John Philip　

14. Pore Volume　

14.1. Definitions　

14.2. Illustration of Breakthrough Curves and Pore Volumes　

14.3. Mathematical Analysis of Pore Volume　

14.4. Calculation of a Pore Volume　

14.5. Pore Volumes Based on Length Units　

14.6. Miscible Displacement　

14.7. Relation between Mobile Water Content and Pore Volume　

14.8. Appendix: Biography of Donald Nielsen　

15. Root Anatomy and Poiseuille's Law for Water Flow in Roots　

15.1. Root Anatomy　

15.2. Poiseuille’s Law　

15.3. Assumptions of Poiseuille’s Law　

15.4. Calculations of Flow Based on Poiseuille's Law　

15.5. Agronomic Applications of Poiseuille’s Law　

15.6. Appendix: Biography of J.L.M. Poiseuille　

15.7. Appendix: Biography of Osborne Reynolds　

15.8. Appendix: Biography of Katherine Esau　

16. Gardner's Equation for Water Movement to Plant Roots　

16.1. Description of the Equation　

16.2. Assumptions　

16.3. Values for the Rate of Water Uptake　

16.4. Examples　

16.5. Effect of Wet and Dry Soil　

16.6. Effect of Root Radius　

16.7. Comparison of Matric Potential at Root and in Soil for Different Rates of Water Uptake　

16.8. Effect of Root Distribution on Wilting　

16.9. Final Comment　

16.10. Appendix: Biography of Wildford Gardner　

17. Stem Anatomy and Pressure–Volume Curves　

17.1. Stem Anatomy　

17.2. Measurement of the Components of the Water Potential　

17.3. Osmotic Potential (Ψs)　

17.4. Theory of　Scholander　Pressure–Volume Curves　

17.5. How to Analyze a Pressure–Volume Curve　

17.6. Turgor Potential (Ψp)　

17.7. Measurement of Plant Water Content and Relative Water Content　

17.8. Osmometer　

17.9. Appendix: Biography of Wilhelm Pfeffer　

17.10. Appendix: Biography of Jacobus　van't　Hoff　

17.11. Appendix: Biography of Rudolf Clausius　

18. Thermocouple Psychrometers　

18.1. Relation between Water Potential and Relative Humidity　

18.2. Thermoelectric Effects　

18.3. Joule Heating　

18.4. Thermoelectric Power　

18.5. Relationship between Vapor Pressure and Temperature　

18.6. Calibration　

18.7. Importance of Isothermal Conditions when Making Measurements　

18.8. Types of Thermocouple Psychrometers　

18.9. Appendix: Biography of J.C.A. Peltier　

18.10. Appendix: Biography of James Prescott Joule　

18.11. Appendix: Biography of William Thomson, Baron Kelvin　

19. Pressure Chambers　

19.1. Comparison of Measurements Made with the Pressure Chamber and the Thermocouple Psychrometer　

19.2. Advantages and Disadvantages of the Pressure Chamber　

19.3. Hydraulic Press　

19.4. Pump-up Pressure Chamber　

19.5. Appendix: Biography of Per　Scholander　

19.6. Appendix: Biography of John Boyer

20. The Ascent of Water in Plants

20.1. The Problem　

20.2. How Water Gets to the Top of Tall Buildings and Animals　

20.3. Cohesion Theory　

20.4. Limitations of the Cohesion Theory　

20.5. Alternative Theories to the Cohesion Theory　

20.6. New Techniques to Confirm the Cohesion Theory　

20.7. Controversy about the Cohesion Theory　

20.8. Potentials in the Soil–Plant–Atmosphere Continuum　

20.9. Appendix: Biography of Henry Dixon　

20.10. Appendix: Biography of John Joly　

21. Sap Flow　

21.1. Heat-Pulse Method　

21.2. Heat-Balance Method　

21.3. Appendix: Biography of C.H.M. van Bavel　

22. Electrical Analogs for Water Movement through the Soil–Plant–Atmosphere Continuum　

22.1. The Analogy　

22.2. Measurement of Resistance with the Wheatstone Bridge　

22.3. Law of Resistance　

22.4. Units of Electrical Conductivity　

22.5. Example of an Electrical Analog Applied to Soil with Wormholes　

22.6. van den Honert's Equation　

22.7. Proof of van den Honert's Equation　

22.8. Appendix: Biography of Georg Ohm　

22.9. Appendix: Biography of Charles Wheatstone　

22.10. Appendix: Biographies of Members of the Siemens Family　

23. Leaf Anatomy and Leaf Elasticity　

23.1. Leaf Anatomy　

23.2. Internal Water Relations　

23.3. Elasticity　

23.4. Elasticity Applied to Plant Leaves　

23.5. Appendix: Biography of Robert Hooke　

23.6. Appendix: Biography of Thomas Young　

24. Stomatal Anatomy and Stomatal Resistance　

24.1. Definition of Stomata and Their Distribution　

24.2. Stomatal Anatomy of Dicots and Monocots　

24.3. Stomatal Density　

24.4. Diffusion of Gases through Stomatal Pores　

24.5. Guard Cells　

24.6. Mechanism of Stomatal Opening　

24.7. Boundary Layer　

24.8. Leaf Resistances　

24.9. Measurement of Stomatal Aperture and Stomatal Resistance　

24.10. Theory of Mass-Flow and Diffusion Porometers　

24.11. Appendix: Biography of Adolf Fick

25. Solar Radiation, Black Bodies, Heat Budget, and Radiation Balance　

25.1. Solar Radiation　

25.2. Terrestrial Radiation　

25.3. Definition of a Black Body　

25.4. Example of a Black Body　

25.5. Temperature of a Black Body　

25.6. Gray Body　

25.7. Spectrum of a Black Body　

25.8. Sun's Temperature　

25.9. Earth's Temperature　

25.10. Comparison of Solar and Terrestrial Radiation　

25.11. Heat Budget　

25.12. Radiation Balance　

25.13. Appendix: Biography of Gustav Kirchhoff　

25.14. Appendix: Biography of Josef Stefan　

25.15. Appendix: Biography of Ludwig Boltzmann　

25.16. Appendix: Biography of Wilhelm Wien　

26. Infrared Thermometers　

26.1. Infrared Thermometers　

26.2. Definitions　

26.3. Principles of Infrared Thermometry　

26.4. Use of a Portable Infrared Thermometer　

26.5. Calibration of Infrared Thermometers　

26.6. Advantages of Infrared Thermometers　

26.7. Appendix: Biography of Ray Jackson　

27. Stress-Degree-Day Concept and Crop Water Stress Index　

27.1. SDD Procedure　

27.2. Canopy-Minus-Air Temperature and Evapotranspiration

27.3. Crop Water Stress Index

27.4. How to Calculate the Crop Water Stress Index

27.5. Crop Water Stress Index for Alfalfa, Soybeans, and Cotton

27.6. Importance of a Wide Range of Vapor Pressure Deficit Values

27.7. Normalized Difference Vegetation Index

27.8. Appendix: Biography of Sherwood Idso

28. Potential Evapotranspiration

28.1. Definition of Potential Evapotranspiration

28.2. Factors that Affect Potential Evapotranspiration

28.3. Advection

28.4. Example Calculation to Determine Potential Evapotranspiration

28.5. Appendix: Biography of Howard Penman

29. Water and Yield

29.1. de Wit's Analysis

29.2. Relationship Between Yield and Transpiration and Yield and Evapotranspiration

29.3. Water and Marketable Yield

29.4. Water and Quality

29.5. Crop Water-use Efficiency

29.6. Water-use Efficiency Under Elevated Carbon Dioxide

29.7. Appendix: Biography of Cornelius de Wit

30. Solar Time and Interception of Direct-Beam Solar Radiation

30.1. Time of Day

30.2. Interception of Direct-Beam Solar Radiation

30.3. How to Measure Altitude and Azimuth Angles of Sun

30.4. Appendix: Biography of Johannes Kepler

31. Soil and Plant Water Relations under Microgravity

31.1 Fundamental Forces of Nature

31.2 Soils

31.3 Plants

31.4 Center of Gravity (Center of Mass)

31.5 Specific Gravity

31.6 Problems

31.7 Appendix: Biography of Galileo Galilei