Development of class pedotransfer functions of soil water retention—A refinement

This paper reviews an existing method of class pedotransfer function development, ‘the Wösten method’, reproducing previous results by this method, and introduces a statistically more stringent refinement, ‘the Transformation method’. Direct comparison of the Wösten method and a Box–Cox Transformation method shows that these two methods produce equivalent predictions of the average values of water retention, and errors in these predictions are also equivalent. However, the Box–Cox Transformation method produces significantly less biased results than the Wösten method at all sampled points along the water retention curve. On average, the Wösten method is more than five times (topsoil), three times (subsoil) and one-and-a-half times (organic) as biased as the Box–Cox Transformation method.