Polyphase moisture transfer as influenced by potential and thermal gradients in a vertisol

Abstract

Water content changes and soil water flux profiles as influenced by temperature gradients at soil depth intervals for 60 days in a packed laboratory column containing a vertisol were measured and compared with predicted values. The rate of increase of isothermal vapour diffusivity with decrease in water was faster than for thermal vapour diffusivity at relatively low moisture content (<0.30 cm3 cm-3), and the observed thermal vapour diffusivity values in dry soil (0.24 cm3cm-3) were about 10 times greater than those in wet soil. The measured high water flux (0.42 cm day-') was concomitant with the increased liquid diffusivity. Water flux decreased sharply at all depths initially, but after about 24 days it decreased gradually with time. The curve of cumulative evaporation versus square root of time in days exhibited a linear relationship up to 13th day.