This paper presents an evaluation of methods for the calculation of the thermal conductivity of soil on the basis of comparison of the thermal conductivity of sand, clay and peat, measured and calculated from the statistical-physical model and de Vries model. For loam, the evaluation was performed on the basis of comparison of results obtained experimentally, models, Laplace transform, and the method of null-alignment, with and without taking into account the thermal conductivity resulting from water vapour movement due to temperature gradient in the soil. The methods presented can be used alternatively for the determination of thermal conductivity if no high temperature gradients occur in the soil and if it can be assumed that the effect of water vapour on the overall effect of conductivity is slight. With high temperature gradients and high rates of water vapour flow in the soil, the statistical-physical and the de Vries models should be used, the latter requiring considerable care, especially in the determination of weight values.