Thermal characterization of a tropical rice soil in relation to puddling, flood-water depth and percolation rate

Abstract

Effects of puddling, flood-water depth and percolation rate on the thermal properties of a tropical rice soil were studied under field and glass-house conditions. Puddling increased volumetric heat capacity (C V), but decreased thermal conductivity (Kt), thermal diffusivity (Dt) and damping depth (D) compared to a nonpuddled soil. A percolation rate of 40 mm d −1 showed higher Kt, Dt and D than zero percolation. The values of Kt, Dt and D were highest with 50 mm and lowest with 10 mm flood- water depth. The C v did not change with different flood-water depths or percolation rates. Consequently, puddling, 40 mm d −1 percolation and 50–100 mm submergence kept the maximum temperature of surface 100–150 mm soil at relatively low level under tropical conditions. These treatments also buffered soil against extreme diurnal temperature fluctuations. The time lag between maximum solar radiation and maximum temperature of submerged soil varied, on an average, between 1.2 hours at soil surface and 11.6 hours at 300 mm soil depth; which is more than that in an upland soil.