CONTENTS 



Page 



INTRODUCTION 1 



STATE OF WATER IN THE SOIL-PLANT-ATMOSPHERE CONTINUUM 2 



Theoretical Considerations 2 



Components of Water Potential 3 



METHODS OF MEASURING WATER POTENTIAL 5 



Nonpsychrometric Methods 5 



The Thermocouple Psychrometer Method 5 



IMPROVED DESIGN CRITERIA FOR THERMOCOUPLE PSYCHROMETERS .... 10 



Considerations of Instrument Design 10 



Construction and Equipment 11 



Calibration and Measurement Procedures 13 



Psychrometer Response to Changing Water Potentials 16 



DISCUSSION 18 



Evaluation of Thermocouple Ps}^chrometers 18 



Potential Uses of Thermocouple Psychrometers 19 



LITERATURE CITED 21 



APPENDIX 23 



