The temperature variations in the upper soil layer are determined by the heat flux density at its surface and the thermal properties of the soil. The thermal properties of the soil depend on the soil water content, the bulk density and structure. Under field conditions these factors vary with depth and time, frequently as a result of agricultural operations such as irrigation or tillage, thus imposing a system which is non-homogeneous and anisotropic in nature.

Part of the book series: Ecological Studies (ECOLSTUD,volume 4)