Gold standards for substrate physico-chemical characterization

Substrates used as growing media vary widely in their physical and hydraulic properties, which affects their suitability for cultivating plants with minimal water and nutrient losses. It is therefore important to identify characterization methods that provide suitable information about substrate properties while being easy to use. Many different measurement techniques have been developed over time to characterize various physical and hydraulic properties of soilless substrates. These measurements provide information about particle and pore sizes, water storage properties, infiltration and gas exchange characteristics, and the elemental composition and chemical attributes of the substrate. This review compiles and categorizes the most relevant physical and chemical properties associated with growing media, discusses the best approaches (i.e., gold standards) for characterization, offers alternative methods that may be useful in certain situations, and considers similarities and differences from approaches used by soil physicists that typically work with mineral soils. The review concludes with new opportunities and modifications that can lead these methods to become more widely adopted.