The process of deriving the hydrological characteristics of a soil to param
eterize a model at the Field scale is not straightforward, especially when
various experimental procedures are used to estimate the parameter values.
This paper shows the inconsistencies that were encountered when attempting
to find the physical and hydrological parameters of two deep loam soils. Th
e parameters were searched for with the aim, and the constraint, of compili
ng the input file of the LEACHM model, which implements a Campbell's modifi
ed K-theta-psi function approach. The soil water content at saturation was
not consistent with the total porosity calculated from measured bulk and pa
rticle densities. The water retention curve (RC) measured in the laboratory
and the conductivity curve measured in the field were described using modi
fied Campbell functions that were separately parameterized, and results wer
e then compared. The optimized values obtained for the theta-psi curve were
remarkably different from those for the K-psi curve. Considering the physi
cal nature of a model and the measurability of its parameters as the basic
requirements for extending model predictions to sites where validation cann
ot be provided, possible solutions are to derive all soil properties simult
aneously on the same sample and/or with a cofitting procedure, to adjust th
e measured values of the soil properties to the functional values, in order
to combine the measured soil properties with the code requirements, and to
modify the code to allow a separate parameterization of the two curves.