Waterafstotendheid: een veel voorkomend verschijnsel in de natuur : Voortschrijdend inzicht in het fenomeen waterafstotendheid

Before 1988 soil investigators generally assumed that the dry topsoil from "nollen" (small dunes) in sandy grasslands was only a consequence of a too deep groundwater table. The bad grass performance should be due to the minor capillary rise of the groundwater towards the topsoil. An explanation for the relatively low water contents in the topsoil after several rain events or sprinkler irrigation applications could not be given at that time. However, in 1988 a second important factor for this phenomenon was determined, namely the extreme water repellency of the topsoil during dry periods. This explained that water infiltrates slowly into the dry topsoil and therefore could flow from the higher nollen to the lower environment. Although not interrogated the occurrence of water repellency, Dr. G.P. Wind showed, in the middle of the seventies of the past century, how application of the detergent Lodaline accelerated the infiltration of rainwater in the soil of his sandy garden. During the last twenty-five years, we performed several studies concerning the prevention of water repellency and the effect of the treatments with surfactants on the wetting and grass performance of sandy soils. Between 1910 and 1970, publications concerning soil water repellency appeared occasionally. After this period, the number of publications increased and resulted in around 100 publications each year during the period between 2000 and now. Although the hydrological importance of water repellency in soils attracted much interest, relatively few studies spent attention to the significance of water repellency of plants. Twenty years ago it was shown that the leaves of the Lotus flower were superhydrofobic and self-cleaning. But also, several animals have superhydrofobic properties that enable them to collect water for drinking.