Thermal conductivity follows the order

Thermal conductivity can be defined as the rate at which heat is transferred by conduction through a unit cross-section area of a material when a temperature gradient exits perpendicular to the area.
Its value depends on factors like soil type, composition, structure, bulk density, porosity, moisture content, and temperature.
Thermal conductivity follows the order for different soil types that is: Sand > loam > clay > peat.
It refers that sand has the highest thermal conductivity whereas peat has the lowest.