Using Pedotransfer Functions to Estimate the van Genuchten–Mualem Soil Hydraulic Properties: A Review

Abstract

We reviewed the use of the van Genuchten–Mualem (VGM) model to parameterize soil hydraulic properties and for developing pedotransfer functions (PTFs). Analysis of literature data showed that the moisture retention characteristic (MRC) parameterization by setting shape parameters m = 1 − 1/n produced the largest deviations between fitted and measured water contents for pressure head values between 330 (log10 pressure head [pF] 2.5) and 2500 cm (pF 3.4). The Schaap–van Genuchten model performed best in describing the unsaturated hydraulic conductivity, K The classical VGM model using fixed parameters produced increasingly higher root mean squared residual, RMSR, values when the soil became drier. The most accurate PTFs for estimating the MRC were obtained when using textural properties, bulk density, soil organic matter, and soil moisture content. The RMSR values for these PTFs approached those of the direct fit, thus suggesting a need to improve both PTFs and the MRC parameterization. Inclusion of the soil water content in the PTFs for K only marginally improved their prediction compared with the PTFs that used only textural properties and bulk density. Including soil organic matter to predict K had more effect on the prediction than including soil moisture. To advance the development of PTFs, we advocate the establishment of databases of soil hydraulic properties that (i) are derived from standardized and harmonized measurement procedures, (ii) contain new predictors such as soil structural properties, and (iii) allow the development of time‐dependent PTFs. Successful use of structural properties in PTFs will require parameterizations that account for the effect of structural properties on the soil hydraulic functions.

A selection of sensing techniques for mapping soil hydraulic properties

“…Vereecken et al (2010), Wösten et al (1999) and Wösten et al (2001) use the following explanatory variables in pedo-transfer functions to predict Mualem-Van Genuchten parameters from soil variables:…”

“…The parameter values of these equations can be predicted from soil properties by using pedo-transfer functions (Bouma, 1989;Vereecken et al, 2010). These soil properties include clay content, loam content, organic matter content and the median grain diameter of the sand fraction (50-2000 µm).…”

Folyadék-visszatartás, folyadékvezetés és porozitás összefüggései vízzel és/vagy szerves folyadékkal telített talajokban I. Folyadék-visszatartó képesség — Szemle

“…A függ-vényparaméterek fizikai tartalma elsősorban akkor értelmezhető, ha az illesztés során a kiindulási és határértékek adottak (pl. VAN GENUCHTEN, 1980;VEREECKEN et al, 2011). A különféle függvények illesztési paraméterei egymásba átszámítható-ak (pl.…”

“…A talaj hidraulikai jellemzőit becslő PTF-ek képzése és fejlesztése során felhasználható talajjellemzők feltérképezésének és a változók közötti kapcsolatok vizsgálatának eredményei számos összefoglaló műben megtalálhatók (PACHEPSKY & RAWLS, 2004;RAJKAI, 2004;SAXTON & RAWLS, 2006;VEREECKEN et al, 2011). A PTF-ekkel végzett becslő eljárások pontosságát és megbízhatóságát kifejező statisztikai mutatókról (determinációs együttható, empirikus szórás, standard hiba számítása stb.…”

The best mathematical models describing particle size distribution of soils

“…Also, soil erodibility, water retention, residual water content, specific surface area, permeability and saturated as well as unsaturated hydraulic conductivity (Vereecken et al 2010;Nimmo 2004;Vipulanandan and Ozgurel 2009) are affected by PSD. Su et al (2004) believed that changes in PSD can provide important indications on the impact of land use, desertification processes and soil degradation on soils.…”