New measurement methods and devices and evaluation framework for characterizing of hydrological properties of growing media

Abstract

Background: Hydraulic properties of horticultural substrates are important variables for a comprehensive evaluation of its performance for horticultural application. The commonly used measurement and evaluation methods and devices are outdated. Objective: 1. Test of new measurement methods and devices (EEM, HYPROP) for quantifying the water and air capacity, the hydraulic conductivity, the shrinkage and rewetting. 2. Development of a rating framework to assess the hydraulic suitability of substrates used in horticulture. Materials and methods: The hydraulic properties of 36 commercial horticultural substrates were quantified and evaluated. Results: EEM and HYPROP enable the simultaneous and effective measurement of the water retention curve and the unsaturated hydraulic functions. Furthermore, the shrinkage properties and the water rewetting time were measured. A rating framework for evaluating the hydraulic quality of horticultural substrates was developed and successfully tested within a comparison of 36 commercial horticultural substrates. Conclusion: The applied methods proved to be suitable. The hydraulic performance of totally peat-free substrates was not worse than those containing peat. The most sensitive element of horticultural substrates was the air supply, especially for cultivation in shallow containers. The proposed evaluation framework provides an opportunity to compare the hydraulic properties of different composed substrates.