Soil Thermal Property Values As a Function of Water Content and Bulk Density.

Soil thermal properties play an important role in soil heat and mass transfer. Thermal properties change as a function of water content and bulk density, the latter being particularly relevant in recently tilled soils. An increase in soil bulk density is associated with smaller saturated volumetric heat capacity and larger saturated thermal conductivity. The objective of this study is to measure soil thermal properties as a function of water content and bulk density. A central Iowa glacial till field site was rototilled to decrease surface layer bulk density and kept bare during subsequent natural wetting and drying cycles. Rainfall tended to cause soil consolidation and increase soil bulk density. Following each rainfall event, undisturbed soil cores were collected and transported to the laboratory for measurements of thermal properties at controlled water content values. A heat pulse sensor was used to measure soil thermal properties at saturated and oven-dry conditions, as well as at water contents corresponding to -50 kPa matric potential. Soil thermal diffusivity, volumetric heat capacity and thermal conductivity did vary as a function of water content and bulk density.