EXPERIMENTAL CORRECTIONS OF SIMPLIFIED METHODS FOR PREDICTING WATER-RETENTION CURVES IN CLAY-LOAMY SOILS FROM PARTICLE-SIZE DETERMINATION

The Arya and Paris model for predicting soil water retention curves fr om particle-size distribution data is a commonly accepted method for r igid soils with medium grain size but limitations to its application f or fine textured soils occur, due to the dominant role of internal str ucture in such soils. Moving from the consideration that simplified mo dels for determining soil hydraulic characteristics may be usefully ad opted to reduce laboratory investigation costs, in this study an attem pt is made to extend the Arya-Paris formulation to clay-loamy soils by means of an experimental calibration function which takes into accoun t the effective soil water retention behaviour. The methodology is bas ed on an inversion procedure of the Arya-Paris model from observed val ues of water retention and potential during evaporation processes on u ndisturbed soil columns. It has been found that the resulting calibrat ion function is typical for each soil and it substantially improves th e prediction of the soil water retention curve from textural informati on. (C) Elsevier Science B.V. All rights reserved.