Estimating water retention characteristic from soil particle-size distribution using a non-similar media concept

Soil water retention characteristic is an important property of soil, Indirect estimation of this property using easily measurable soil properties remains the research focus of many soil scientists. In this study, a general approach was proposed to derive soil water retention characteristic from soil particle-size distribution and bulk density using a non-similar media concept. Effectiveness of the developed model was tested against measured water retention data of 130 sieved soils with textures ranging from sand to heavy clay. The values of the root mean square error (RMSE) between estimated and experimental pressure heads ranged from 0.4340 to 0.7287 Log cm H2O for all 11 soil textual classes tested in this study. In addition, the new model was compared with the Arya-Paris model, and the results showed that the proposed approach could reduce the overall estimation deviation significantly. The comparison in terms of RMSE values indicated that for 61% of the soils, estimations by the new model were better than those by the best one of the three approaches of the Arya-Paris model, and for about 10% of the soils, the results using the two models were similar. Evidently, the proposed model employs a simple calculation procedure and applies well to soils of all textures except sandy soils. (Soil Science 2001;166:308-321).