Rose (Rosa sp.) plants (`Mercedes') were grown in yellow tuff (YT) (volcanic ash, scoria) and pumice from Italy (PI) and Greece (PG) for which physical and hydraulic characteristics were determined. The differences among the measured retention curves of these materials result in significant differences among their relative hydraulic conductivity functions. The hydraulic conductivity of YT is much higher than that of PI, which is higher than that of PG. The plants were subjected to optimal growth and nutrition conditions. Irrigation was controlled using electronic tensiometers, at suction values well within the range of easily available water: 13 cm for YT and 8 cm for the two pumice types. Nonetheless, yields were significantly higher in YT than in PI; yields were even lower in PG. We suggest that the limiting factor was the dynamic water availability to the plants, which is affected mainly by the unsaturated hydraulic conductivity. The relative hydraulic conductivity of YT at 13 cm is more than an order of magnitude higher than that of PI at 8 cm. The relative hydraulic conductivity of PG at 8 cm is two orders of magnitude lower than that of YT at 13 cm. It seems that the current concept of easily available water, based on a predetermined suction range, independent of the hydraulic characteristics of the media, is not an appropriate parameter for irrigation management in soilless culture. The unsaturated hydraulic conductivity, being a characteristic function of the medium and highly sensitive to moisture variation, indicates better the actual availability of water to the roots. Therefore, it should be used for irrigation control in containers filled with porous substrates.
hydraulic properties of pumice affect growth and yield of greenhouse crops in soilless culture HortScience 42 1274 1280 10.21273/HORTSCI.42.5.1274 Karlovich, P.T. Fonteno, W.C. 1986 The effect of soil moisture tension and volume moisture on the growth of
. 23–38. In: D.W. Robinson and J.G.D. Lamb (eds.). Peat in horticulture. Academic Press, London, UK Raviv, M. Lieth, J.H. 2008 Soilless culture theory and practice. Elsevier, San Diego, CA Raviv, M. Wallach, R. Silber, A. Medina, S. Krasnovsky, A. 1999
—An integrating plant behaviour Plant Cell Environ. 22 1463 1473 10.1046/j.1365-3040.1999.00514.x Wallach, R. 2008 Physical characteristics of soilless media 41 116 Raviv M. Lieth J.H. Soilless culture: Theory and practice Elsevier, Amsterdam The Netherlands Yeh