Errors in Heat Flux Measurement by Flux Plates of Contrasting Design and Thermal Conductivity

using flux plates to measure G, including (i) heat flow distortion near the plate, (ii) liquid water and vapor The thermal conductivity () of soils may vary by a factor of about flow divergence, and (iii) underestimates of G because 4 for a range of field soil water contents. Measurement of soil heat flux (G ) using a heat flux plate with a fixed distorts heat flow of poor thermal contact between the plate and soil ma- through the plates and in the adjacent soil. The objectives of this trix (Philip, 1961; Fuchs and Hadas, 1973; Mayocchi and research were to quantify heat flow distortion errors for soil heat flux Bristow, 1995). Heat flow distortion near flux plates plates of widely contrasting designs and to evaluate the accuracy of occurs because the plate is constructed of materials with a previously reported correction. Six types of commercially available fixed thermal conductivity () under ambient conditions heat flux plates with varying thickness, face area, and thermal conduc- while soil is influenced by mineral type, particle size tivity (m) were evaluated. Steady-state laboratory experiments at flux and arrangement, organic matter content, bulk density, densities from 20 to 175 W m 2 were completed in a large box filled and especially soil water content (de Vries, 1963; Far- with dry or saturated sand having of 0.36 and 2.25 W m 1 K 1 .A ouki, 1986; Bristow, 2002). Soil may range from 0.2 field experiment compared G measured with pairs of four plate types