Pedotransfer functions to estimate soil water retention parameters for a modified Brooks-Corey type model

This paper presents pedotransfer functions to estimate soil water retention parameters of the Hutson-Cass modified form of the Brooks-Corey equation from soil texture, bulk density and organic carbon content. Multiple regression equations are developed from a subset (286 soil horizons) of the soil physical properties database of England and Wales. For this dependent dataset, the average root mean square error (RMSE) in soil water content was 0.043 m(3) m(-3) while ca. 68% of the entries had RMSE values less than 0.05 m(3) m(-3). The functions were then validated against the remaining 1678 soil horizons in the database. This independent test gave a mean RMSE nearly as small (0.048 m(3) m(-3))as that obtained for the original dataset. This degree of accuracy is considered acceptable, given the simple form assumed for the water retention function. The functions were shown to be robust, except for organic horizons (organic carbon content > 5%) and/or for soils of small bulk density (< 0.9 g cm(-3)). Published by Elsevier Science B.V.