An Empirical Model for Estimating Soil Thermal Conductivity from Texture, Water Content, and Bulk Density

Soil thermal conductivity (λ) models are needed frequently in studying coupled heat and water transfer in soils. Several models are available, but some are complicated and some produce relatively large errors. In this study, we developed a simple model for estimating λ from soil texture, bulk density (ρ b ), and water content (θ). Three parameters, α, β, and λ dry , are included in the model, where λ dry is determined by ρ b and α and β are shape factors estimated from soil texture and ρ b . Empirical relations were developed for α and β by fitting the model to heat‐pulse (HP) measurements of λ(θ) on seven soils of various textures. The model performance was evaluated with independent λ(θ) data from independent HP measurements and literature values. The results show that the model is able to express the λ(θ) curves from oven dry to saturation at fixed ρ b values. When ρ b is varied, the estimated λ data agree well with measured values. The root mean square errors are <0.15 W m −1 K −1 , and the bias is within 0.10 W m −1 K −1 . The new model has the potential for use in studying heat movement in soils of varying texture, bulk density, and water content and can be incorporated into numerical algorithms for describing coupled heat and mass transfer processes.