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 f rom soil texture, bulk density and organic carbon content. Multiple regress ion equations are developed from a subset (286 soil horizons) of the soil p hysical properties database of England and Wales. For this dependent datase t, the average root mean square error (RMSE) in soil water content was 0.04 3 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 de gree of accuracy is considered acceptable, given the simple form assumed fo r the water retention function. The functions were shown to be robust, exce pt for organic horizons (organic carbon content > 5%) and/or for soils of s mall bulk density (< 0.9 g cm(-3)). Published by Elsevier Science B.V.