• journal_title：Vadose Zone Journal
• Contributor：A. L. B. Hurtado ; Q. de Jong van Lier
• Publisher：Soil Science Society of America
• Date：2005-
• Format：text/html
• Language：en
• Identifier：10.2113/4.1.151
• journal_abbrev：Vadose Zone Journal
• issn：1539-1663
• volume：4
• issue：1
• firstpage：151
• section：ORIGINAL RESEARCH

Unsaturated hydraulic conductivity (K) can be expressed as a function of soil water content (θ) or pressure head (h). Methods to determine K often give highly variable results, thus making it difficult to report values for K in a reliable manner. Due to the sensitivity of pore conductivity to pore radius, it can be expected that K expressed as a function of h shows less variability than expressed as a function of θ. To test this hypothesis, K was determined at several values of θ and h using the instantaneous profile method at 48 locations in the surface and a subsurface layer of a Typic Hapludox in Brazil. Results were analyzed considering the field values of K at the time of observation (K_t), at fixed values of θ (K_θ), and at fixed values of h (K_h). Results show that the coefficient of variation of K_θ is higher than that of K_h, especially in the surface layer, which suggests that, if one has the choice, it would be preferable to estimate soil water movement using measured h values, and using K(h), instead of measuring θ and using K(θ). We also show that the variability in K_t increases as the soil gets drier, while K_θ and K_h show more variability for wetter soil.