Comparison of class and continuous pedotransfer functions to generate soil hydraulic characteristics

Abstract

Class pedotransfer functions were used to generate average hydraulic characteristics for distinct soil texture classes. Continuous pedotransfer functions were used to generate soil hydraulic characteristics from the actually measured median of the sand particle size, bulk density and percentages clay, silt and organic matter. Both approaches were used to predict the soil physical input data to calculate five different functional aspects of soil behaviour. The functional aspects were: number of workable days, number of days with adequate soil aeration, elapsed time until 10% breakthrough of chloride, amount of cadmium leached after one year and amount of Isoproturon leached after one year.Simulations of water and solute transport were made for 88 profiles which form a statistically representative set of profiles for cover sands in the northeastern part of the Netherlands. The calculated number of workable days did not depend on the type of pedotransfer used. However, the differences between the class and continuous pedotransfer function approach were significant for the other four functional aspects of soil behaviour. For adsorbing cadmium and adsorbing and degradable Isoproturon, differences between the two approaches were statistically significant because they were systematic. However, these differences were so small that they were irrelevant in practice. When to prefer which approach was ambiguous and depended on the functional aspect under consideration. When differences were not significant or irrelevant in practice, the cheaper and easier to use class pedotransfer function approach is preferred over the continuous pedotransfer function approach.

Consequences of varied soil hydraulic and meteorological complexity on unsaturated zone time lag estimates

“…Similarly, increasing the complexity of data inputs to a model, such as by moving from pedotransfer functions to measured data, can likewise improve the performance of that model. Wösten et al (1995) suggested that more complex soil data be employed only when the differences in estimates of soil behaviour were significant as a consequence. Mohamed and Ali (2006) found that using more detailed input data in PTFs increased their reliability.…”

Pedotransfer functions for point and parametric estimations of soil water retention curve

“…Vereecken et al (1992) found that estimation accuracies of PTFs for van Genuchten parameters ranged between 0.560 and 0.848 (R 2 ). Wösten et al (1995) derived PTFs for estimation of these parameters in sandy soils with the accuracy of R 2 = 0.71, 0.53, and 0.63 for θ s , α, and n, respectively. Wösten et al (2001) reported that the equation accuracies were 0.76, 0.20, and 0.54 for the same parameters.…”

“…In point estimation, soil water contents are estimated at selected water potentials (Batjes 1996, Pachepsky et al 1996, Minasny et al 1999. The parameterization method estimates the parameters of soil water retention models (Vereecken et al 1992, Wösten et al 1995, Schaap et al 1998, Minasny and McBratney 2002. Two of the most commonly used water retention models are van Genuchten (1980) and Brooks and Corey (1964).…”

Talajok víztartó képességét becslő módszerek

“…A talajcsoportok kialakítása többféleképpen történ-het. A módszerek többségében a fizikai féleség adja az osztályozás alapját BRUAND et al, 2003;TÓTH et al, 2005;PACHEPSKY et al, 2006;BAKER, 2008;WÖSTEN et al, 1995). Csoportképző lehet még a talaj szervesanyag-tartalma , szerkezete (PACHEPSKY & RAWLS, 2003), a talaj altípusa (TÓTH et al, 2005;MAKÓ & TÓTH, 2007), vagy taxonómiai kategóriája (BATJES, 1996;), a feltalaj és az altalaj (WÖSTEN et al, 1990;RAWLS et al, 2001), vagy a talajképző kőzet (PACHEPSKY & RAWLS, 2004).…”