Evaluation of soil pore-water salinity using a Decagon GS3 sensor in saline-alkali reclaimed tidal lands

The electrical conductivity of soil pore-water solution (ECp) to moderate salinity can be computed from the bulk EC (ECb) without calibration.GS3 soil salinity sensors, if optimally calibrated, can be effectively used to monitor salt behavior in saline soils. This study develops general equations to extend the applications of a GS3 salinity sensor to a wide range of soils including critical saline-alkali reclaimed tidal lands. The GS3 sensor measures volumetric water content, temperature, and electrical conductivity independently. As a result of laboratory-based sensor calibration testing, it was determined that the electrical conductivity of soil pore-water solution (ECp) with slight to moderate salinity can be computed from the bulk EC (ECb) without calibration. The ECb data obtained from the sensors were reconstructed via the calibration equation. We compared these results to ECp observed from suction cup samples. A good correlation was observed between the calibrated ECp and the observed ECp, in low-to high-salinity soils. However, the calibrated ECp at very high salinity underestimates the observed ECp. Based on these results, we conclude that these sensors offer clear additional value in ensuring control of the root-zone salinity, and in compensating for weather influences.