S06 - Session P16 - The retention time of saturation affects EC measurement using saturated media extract method

Authors: Jaebeom Lee *, Seong Kwang An, Jongyun Kim

For electrical conductivity (EC) measurement of growing media, SME (Saturated Media Extract), 1:2, 1:5, or Pour-through methods are generally used, and the SME method is most frequently used for the experiments with a soilless substrate. SME method measures the EC from the solution by pouring deionized water on the media and saturating it for a certain time, usually 1-2 hours, then extracting. However, the criteria for the saturation time were not clear, and there were different guidelines in the previous literature. The current study compared the measured EC values according to the various retention times using SME, to investigate the potential difference in EC measurements depending on the media saturating time. Coir was used as the soilless substrate, and four EC levels of the substrate were prepared with an aqueous NaCl solution with concentrations at 1, 2, 4, and 8 dS·m -1 . The substrate retention time of saturation was set to 30 min, 1 hr, 2 hr, 12 hr, and 24 hr, respectively, with three replicates. As a result, different retention times led to significantly different EC levels from the SME method ( P Time < 0.001), regardless of the solution EC levels ( P EC×Time = 0.1276). Although there were no differences in the EC values of the extracted solutions among the samples saturated for 30 min, 1 hr, and 2 hr, the EC value was lower in the samples saturated for 12 hr, and the lowest for 24 hr retention time. This result indicated that retention time of more than 2 hr during saturation may provide inconsistent EC values, thus leading to potential misinterpretation of the data. Therefore, a descriptive method for SME should be noted for the reliability of the EC study, and retention time between 30 min to 2 hr would provide consistent EC measurement for the soilless substrate. This work was supported by RDA Korea (PJ015643).