As films become thicker and thicker, the matric potential becomes smaller and smaller. Soil water can be seperated into ranges of matric potentials that exhibit similar behavior and that correlate with observable phenomena. 4.1 Saturation When all the soil pores are filled with water. Corresponds to matric potentials of 0 bars. 4.2 Field capacity Point where the matric potential balances the gravitational potential.
Water ceases to drain out of the soil.
4.4 Hygroscopic coefficient Point where evaporation ceases, and the soil is said to be air dry. Oven dry Point where non-chemically combined water has been removed from the soil. The only water remaining is the water of hydration and other chemically combined water. Corresponds to matric potentials of -10,000 bar. 5-9ab or Fig. 5.28 in Brady and Fig.