WATER REPELLENCY OF ORGANIC GROWING MEDIA ITS INFLUENCE ON HYSTERETIC HYDRAULIC PROPERTIES

摘要

As for soils, most of growing media can present hysteresis phenomena during drying/wetting cycles, which greatly affect hydraulic properties. In case of organic substrates, the acquisition of a hydrophobic character during desiccation can be considered as one of the main factors conditioning hysteresis phenomena. The purpose of this study is then to estimate the influence of the wettability by contact angle measurements (capillary rise method of Michel et al. 2001) on their hydraulic properties (q(y) and K(y)) measured by the Instantaneous Profile Method (IPM) during evaporation and infiltration experiments as well. Peat showed a large evolution of wettability related to water content and important hysteresis phenomena in contact angles measurements but also in the hydraulic conductivity K(y) and water retention q(y)? curves. On the other hand, the wettability of pine bark also varied with water content, but no hysteresis phenomena were observed in contact angles measurement and in the q(y) and the K(y) curves. The whole of these results seemed to indicate that hydraulic properties (water retention and hydraulic conductivity) were influenced by wettability of substrates.