Abstract

A laboratory experiment was conducted with tree texturally different soils (Red loamy sand, Black clay soil and Alluvial sandy loam) in PVC columns maintaining at two bulk density levels to compare the thermal properties as influenced by texture, compaction and mineralogical composition of soils. Difference in peak soil temperature (ST) between surface and 20 cm soil layer reduced by 50% or more with increase in compaction level. Monitoring of ST at hourly interval on different days after saturation showed the highest magnitudes of ST at all depths throughout the day in black clay soil and the lowest in alluvial sandy loam soils.  Magnitude of volumetric heat capacity (C_V) was in the order: Black clay soil (2.25-2.65 × 10⁶Jm^-3K^-1) >alluvial sandy loam soil (1.85-2.27 × 10⁶ Jm^-3K^-1)>red loamy sand soil (1.79-2.22 × 10⁶ Jm^-3K^-1). Magnitude of thermal diffusivity (D) was in the order: black clay soil (1.73-5.33m²sec^-1x 10^-6) >alluvial sandy loam soil (1.04-3.39 m²s^-1 × 10^-6)>red loamy sand soil (0.84-2.36 m²s^-1 × 10^-6). The range of thermal conductivity (K) for was highest for black soil followed by alluvial sandy loam and red loamy sand soil. Thermal properties were the highest for black clay soil followed by alluvial sandy loam soil and were the lowest in red loamy sand soil. In all soil types, C_v and K were higher in compacted soil as compare to loose soil. Hence, downward heat flux was more in compacted soil. The black color of the clay soil might have exerted added effects on the increase in the temperature because of more heat absorption whereas the moderating effect of higher moisture on ST was not prominent. Whereas in lighter colour  alluvial soil  due to moderating effect of soil water on ST  would lead to the reduction evaporational losses and improvement in water use efficiency of crop.

Key words: Soil temperature, thermal conductivity, compaction, soil texture, damping depth.