estimating soil heat flux density

The measurement or estimation of soil heat flux density (G) is often problematic, and accurate values are important for energy balance calculations. Recently, the UN-FAO has published new recommendations on estimating reference evapotranspiration (ETo) for use in irrigation planning using hourly weather data. In their equation, they estimate G under 0.12 m tall grass as a function of net radiation (Rn) as G=0.1Rn during daytime and G=0.5Rn at night. However, the selection of these coefficients came from literature where G was measured only using a heat flux plate without corrections for heat storage above the plate. One aspect of this research was to investigate the relationship between measured G and Rn measured over 0.12 m tall grass using heat flux plates buried at 0.02 and 0.04 m deep both with and without corrections for heat storage above the plates. We also investigated the possibility to estimate apparent thermal conductivity in the field by measuring soil temperature above and below heat flux plates. In addition, the use of apparent thermal conductivity to estimate soil water potential was studied.