THERMODYNAMICS OF WATER MOVEMENT IN THE SOIL

This analysis presents the results of research on the influence of variations in soil water content and soil temperature on the movement of heat and water in the soil. Results were summarized under three phases: (1) Compressibility experiments were carried out to evaluate the influence of soil compaction on the water-retaining strength of the soil. It was found that the latter decreased with increases in soil density and temperature for a particular soil when moisture content, mechanical pressure, and all other composition variables were held constant, (2) Evaporation of soil water under isothermal conditions was measured in a series of experiments to determine the dependence of rate of drying of soil on soil temperature. Dry air was passed over moist soil columns and evaporation was measured over a range of temperatures. Experimental results indicate that the rate of water loss is a function of the heat content of the soil water as well as the rate of water movement within the soil, and (3) Thermal gradient experiments were conducted in the laboratory to determine the functional relationship of the rate of heat and moisture transfer to the temperature gradient in the soil. Movement of water, both in liquid and vapor phases, was from the warm to the cool region in the soil. (Author)