Energy Concept and Thermodynamics of Water in Soil
In 1943, Edlefsen and Anderson published a highly valuable report entitled “Thermodynamics of Soil Moisture.” It was the first systematic study of thermodynamics of water in soil, and it emphasized the importance of the use of chemical potential. The state of water in soil can be described exactly on the basis of thermodynamic concepts such as chemical potential. For discussions of concepts of the first and second laws of thermodynamics, entropy, free energy, and chemical potential, the reader is referred to textbooks on thermodynamics, such as that by Kirkwood and Oppenheim. In 1974, the second Terminology Committee of Commission I of the International Society of Soil Science adopted the total potential as an energy concept to express the state of water in soil. A tensiometer is a useful device for measuring the total potential or the pressure potential the tensiometer pressure potential.