Quantifying hydro-physical properties of growing media with the HYPROP and comparison with the DIN EN standard procedure
The hydro-physical properties and information on air and water management are important for their suitability in horticulture. By default, the determination of the hydro-physical properties of growing media is carried out with the sandbox method. Moreover, the evaluation of the shrinkage behavior takes place on oven-dry samples. A statement about crack formation and shrinkage-induced volume change during use cannot be derived from this. Capillary water transport, rewetting properties and hysteresis of the hydraulic characteristics are not sufficient considered. In this study, the hydro-physical properties NDASH water retention curve and unsaturated hydraulic conductivity - were simultaneously measured with the Extended Evaporation Method (EEM) and the HYPROP device (HYdraulic PROPerty analyzer) on six different growing media. The basic hydro-physical quality indicators- water and air capacity, capillarity- were derived from these functions and compared with DIN EN 13041 results. In addition, shrinkage and re-wettability inhibition were measured during the experiment. The hydro-physical quality evaluation was carried out for the application in flower pots/containers and in the field. The plant available water was sufficient in flower pots for all substrates. Most critical was the air capacity in shallow containers. The air capacity according to DIN EN 13041 varied between 4 and 21% by vol. (on average 11.9% by vol.) and was between 2 and 12% by vol. (on average 7% by vol.) larger than the HYPROP calculations (between 2 and 10% by vol). Based on the air and water content values according to DIN EN 13041, no statement on the water management for field conditions is possible. Hysteresis of the hydraulic functions and the aging behavior of the growing media are important issues for future research.
Schindler, U. and Eulenstein, F. (2021). Quantifying hydro-physical properties of growing media with the HYPROP and comparison with the DIN EN standard procedure. Acta Hortic. 1305, 171-178
air capacity, plant available water, water retention curve, unsaturated hydraulic conductivity function, re-wetting, water drop penetration time, extended evaporation method (EEM)