Miscellaneous Methods for Measuring Matric or Water Potential

Abstract

This chapter describes a variety of techniques to measure matric potential or water potential in the laboratory and in the field. They are heat dissipation sensors, electrical resistance sensors, frequency domain and time domain sensors, electro-optical switches, filter paper method, Dew Point Potentiameter, and vapor equilibration. The first four techniques are electronically based methods for measuring matric potential. The filter paper, Dew Point Potentiameter, and vapor equilibration techniques are generally used in the laboratory to measure water potential of disturbed field samples or to measure water potential for water retention functions. The techniques described require equilibration of some medium whose matric or water potential can be determined from previous calibration or can be measured directly. Under equilibrium conditions the matric or water potential of the medium is equal to that of the soil.