WATER REPELLENCY OF PEATS: A MAIN FACTOR INFLUENCING THE EVOLUTION OF THEIR PHYSICAL PROPERTIES
The knowledge of physical properties over time in horticultural growing media is of vital importance for the effective management of irrigation and fertilization. Water retention, shrink/swell properties and water repellency of a Sphagnum peat growing medium were measured during several drying/wetting cycles with varying intensities (0↔-10 kPa, 0↔-32 kPa). Regardless of the intensity of drying, water retention and shrink/swell properties are mainly modified after the first drying process, resulting in an increase of density and a change in water retention (due to a consolidation in the range of potentials varying between 0 and -3 kPa), whereas these properties are not affected by the other cycles, even if hysteresis phenomena are always shown to take place. In parallel, water repellency (estimated by direct contact angles measurements between -15 and -32 kPa) also showed hysteresis phenomena and was also not affected by the number of cycles. Variations in drying intensity reveal a double porosity (inter and inner porosities), with an inflection point observed around -20 kPa. If hysteresis phenomena are due to the ink bottle effect in the lowest suctions, water repellency can be considered as the most relevant parameters for explaining the hysteresis phenomena in the highest suctions (> -20 kPa).
Michel, J.-C., Qi, G. and Charpentier, S. (2013). WATER REPELLENCY OF PEATS: A MAIN FACTOR INFLUENCING THE EVOLUTION OF THEIR PHYSICAL PROPERTIES. Acta Hortic. 1013, 167-174
peat substrate, shrink/swell, water retention, hysteresis, contact angle