6. Soil-Water Potential and Its Measurement

Soil-water potential expresses quantitatively the energy of soil water (of water in porous medium); the difference between soil-water potentials of two points is necessary a condition to transport soil water from the point of higher to the point of lower soil-water potential. In this chapter, soil-water potential is defined and expressed as a negative value because of binding forces between soil and water. Total soil-water potential and its components (gravitational, matric and pneumatic) are defined, and principles of methods of their measurement are described. The principles underlying piezometer measurement of positive pressure potentials and tensiometer measurement of soil-matric potentials are analyzed, and the techniques of their application in the field are discussed.