Estimation of Hydraulic Properties of Growing Media with a One-Step Outflow Technique

An application of the improved iterative method for the simultaneous determination of the hydraulic properties of growing media using the one-step experiment is described for highly porous media. Substrate hydraulic properties were characterized by the Brooks and Corey equation for water retention, and by the Kozeny power equation for hydraulic conductivity. The iterative procedure has been tested with a particular class of growing media generally used for container plant cultivation, represented by pure peat, pumice, and a 25:75 Peat:Pumice mix. The previously optimized One-Step method with Peat:Pumice ratio in the range from 1:0 to 1:1, was tested on five replications over the new range from 1:3 to 0:1. By analyzing the mean cumulative outflow curves recorded versus time, an estimation of hydraulic functions was derived. Estimated water retention was compared with nine experimental data-sets and with estimation by the Van Genuchten model. Normalizing the saturated water content, the two models overlap except for the "wet" range near saturation. Estimated hydraulic conductivity was compared with the estimation derived from the Van Genuchten-Mualem equation involving 3 and/or 4-parameter analysis. Comparisons showed a good similarity between model estimations.