Results of the performed preliminary particle size determination (PSD) experiments of soils show the importance of the preparation details of the laser diffractometer method (LDM). The analysis of the effect of each preparation factor on soil PSD data calls attention to the need for working out standard instructions defining the pre-treatments and settings for the LDM instrument. Further laboratory experiments involving larger soil datasets are required for the better understanding of the effects of soil pre-treatments and settings on PSD data. There is a practical reason of substituting the time-consuming pipette method with the LDM. In case of this substitution, linkages of the LDM PSD data and other soil properties are to be established. Correlation study of the LDM and conventional PSD data could make the harmonization of newly built and historical databases possible. Finally, the introduction of the LDM technique to soil physical methodology could generate the reevaluation of existing soil physical interrelations.
The Hungarian Detailed Soil Hydrophysical Database, called MARTHA ver2.0 has been developed to collect information on measured soil hydraulic and physical characteristics in Hungary. Recently this is the largest detailed national hydrophysical database, containing controlled information from a total of 15,005 soil horizons. Two commonly used pedotransfer functions were tested to evaluate the accuracy of the predictions on the MARTHA data set, representative for Hungarian soils. In general, the application of both examined pedotransfer functions (Rajkai,
et al., 1999) was not very successful, because these PTFs are representative for other soil groups. The classification tree method was used to evaluate the effect of soil structure on the goodness of estimations. It was found that using the soil structure data the inaccuracies of soil water retention predictions are more explainable and the structure may serve as a grouping variable for the development of class PTFs.