Estimating Soil Hydraulic Properties From Pedotransfer Functions and the Mualem-Van Genuchten Parameterisation: Past, Present and Future.

Knowledge of soil hydraulic properties is mandatory in describing and predicting water flow and solute transport in the vadose zone. Direct determination, despite all developments in measurement techniques, is still expensive, time-consuming and for larger scale applications often not possible. Therefore pedotransfer functions (PTF) were developed that relate soil hydraulic properties to easily measurable soil properties. In many of these functions, the Mualem-van Genuchten models (MVG) have been used to relate the parameters in these equations to soil properties. The development of these functions has contributed enormously to the development of PTF and has boosted the wide spread application of soil water and solute transport models at field and larger scales. In this presentation, we will discuss the state of the art with respect to the development of PTF using the MVG models. We will refer to some of the recent work that re-analyzed the database of soil hydraulic properties established by Vereecken et al. (1989, 1990).