In recent years the question concerning climate changes is discussed more and more as well as the effect of temperature on different factors in biological, agricultural sciences and industry. Thermal properties of the soil determine its warming, the conduction of heat through the soil and its cooling. The investigation of soil thermal properties is studying their changes as a result of irrigation, tillage treatments, comparing together grassed ground and cultivated soils. In the current study thermal properties of two soils, with different soil characteristics, were determined. Field experiments were carried out with maize, soybean and wheat under irrigated and non-irrigated conditions. The change of soil thermal properties at cultivation of different crops in two experimental fields of the Poushkarov Institute of Soil Science was investigated. The received experimental data for mechanical composition, soil organic matter (humus), bulk density, particle density and volumetric water content were used for calculating the thermal properties of the investigated soils. The results show that the values of soil thermal conductivity and thermal diffusivity for meadow-cinnamonic soil in experimental field Tzalapitza, Plovdiv region, are higher and the values of volumetric heat capacity are lower in comparison with leached smolnitza in the experimental field Bojurishte, Sofia region.
