Deriving point and parametric pedotransfer functions of some gypsiferous soils

Abstract

Parametric description of the soil water retention curve as well as the hydraulic conductivity curve is needed for modelling water movement and solute transport in the vadose zone. The objective of this study was to derive pedotransfer functions (PTFs) to predict the water retention curve and the van Genuchten and the van Genuchten–Mualem parameters of some gypsiferous soils. Consequently, 185 gypsiferous soil samples were collected and their physical properties were measured. The particle size distribution was determined in 2 steps: (i) with gypsum, by covering the particles with barium sulphate; (ii) without gypsum, using the hydrometry method. The easily obtainable variables were grouped as (1) particle size distribution, bulk density, and gypsum content; and (2) bulk density, gypsum content, geometric mean, and geometric standard deviation of the particle diameter. Stepwise multiple linear regression method was used to derive the PTFs. Two types of parametric and point functions were derived using these variables. The first group of variables predicted water retention and the van Genuchten and van Genuchten–Mualem parameters better than the second group. The gypsum content appeared to be the second dominant parameter for predicting water retention at 0, −330, −1000, −3000, −5000, and −15 000 cm. The derived PTFs were compared with the Rosetta database as independent dataset. The validity test indicated that in order to predict the hydraulic properties of gypsiferous soils the derived PTFs are more accurate than what can be obtained from the Rosetta database. Removal of gypsum increased the water retention at pressure heads of 0, –100, –330, –1000, –3000, –5000, and –15 000 cm (P < 0.01). The results also indicated that hydraulic parameters were different for the same soil with and without gypsum.

Towards using pedotransfer functions for estimating infiltration parameters

“…In their study, comparison of the derived PTFs with that obtained from Rosetta program (Schaap et al 2001) showed that one should be careful when applying PTFs in pedogenically different areas. The same conclusion was also reported by Homaee and Farrokhian Firouzi (2008) and Cornelis et al (2001). A c c e p t e d M a n u s c r i p t 3 In recent years, development of PTFs for estimating soil hydraulic properties and dielectric properties (Persson et al 2002) has become increasingly popular.…”

Assessing the best performing pedotransfer functions for predicting the soil‐water characteristic curve according to soil texture classes and matric potentials

“…The fifth point PTF evaluated in this study (Homaee & Firouzi, 2008) (PT5) is a logarithmic function (Equation )): …”

“…Two main groups of PTFs for predicting SWCC have been developed: discrete or point PTFs and continuous PTFs. The point PTFs predict the soil water contents at specific matric potentials (e.g., Adhikary et al, 2008; Al Majou, Bruand, Duval, & Cousin, 2007; Costa et al, 2013; Dashtaki et al, 2010; Fooladmand, 2011; Gupta & Larson, 1979; Homaee & Firouzi, 2008; Hua et al, 2011; Obalum & Obi, 2013; Rawls et al, 1982). Continuous PTFs are functions for predicting the parameters of closed‐form equations between soil water content and matric potential (e.g., Brooks & Corey, 1964; Campbell, 1974; Hutson & Cass, 1987; Saxton & Rawls, 2006; Saxton, Rawls, Romberger, & Papendick, 1986; Van Genuchten, 1980).…”

A Comparative Study of Multiple Approaches for Predicting the Soil-Water Retention Curve: Hyperspectral Information vs. Basic Soil Properties

“…The accuracy with which these properties can be estimated has however a significant effect on the quality of predicted soil hydrological fluxes and states (Montzka et al, 2011). Pedotransfer functions are now popularly used to estimate the soil hydraulic functions from basic soil data such as the particle-size distribu-tion, the bulk density, and the organic C content (Vereecken et al, 1989(Vereecken et al, , 1990(Vereecken et al, , 1992(Vereecken et al, , 2010Schaap et al, 1998Schaap et al, , 2001Jarvis et al, 2002;Rawls and Pachepsky, 2002;Pachepsky et al 2006;Jana et al, 2007;Homaee and Farrokhian Firouzi, 2008;Weynants et al, 2009;Ghorbani Dashtaki et al, 2010). Both point and parametric PTFs have been used for this purpose.…”