Physical characteristics of soilless media

Similar to soils, soilless media are composed of three phases: solid, aqueous, and gaseous. The substantial differences between the former and the latter are related to the solid phase composition and associated texture and structure. While the solid phase of soils is mostly minerals, it is a mixture of minerals and organic matter for soilless culture, resulting in substantial differences in their physical and hydraulic properties. The physical and hydraulic properties of soil have been intensively studied, both experimentally and theoretically, the application and implementation of these knowledge and methods to soilless substrates is limited. This chapter aims to close the gaps in physics and hydraulic characterization and application between mineral soils and soilless media by applying terminology, methods, and approaches that are commonly used for the former to the latter. The current version of this Chapter extents the topic of particle wettability and its effect on the physical properties of soilless media. Although research on sales-media wettability and its effect on water retention and flow in the media has only recently initiated, its relevance is essential owing to the high organic matter content of these media and the relationship between the two.