Variation of the water-retention properties of soils: Validity of class-pedotransfer functions

Water-retention properties of soils vary according to soil characteristics, and the understanding of their variation remains controversial. Numerous pedotransfer functions (ptfs) that enable prediction of the water-retention properties of soils were developed, but their validity was poorly discussed. In this study, we compare the performances of textural and texturo-structural class ptfs with more sophisticated class and continuous ptfs developed using the same set of soils. We showed that the former led to prediction performances that are better than, or similar to, those recorded with the more sophisticated class and continuous ptfs studied. Thus, textural and texturo-structural class ptfs that are quite easy to establish are potentially worthwhile tools for predicting the water-retention properties of soils, particularly at scales for which semi-quantitative or qualitative basic soil characteristics, such as the texture, are the only characteristics available. More generally, our results pointed out that the discussion of ptfs performance should refer to those recorded with easy to establish ptfs, thus enabling to quantify how much prediction bias and precision can be gained when increasing the complexity of ptfs and, consequently, the number and quality of predictors required.