Study on capillary rise from shallow groundwater and critical water table depth of a saline-sodic soil in western Songnen plain of China

The objective of this study was to develop an empirical equation for estimating the capillary rise in the saline-sodic soil area of Songnen Plain in China based on the Averianov formula. The capillary rise was observed under five controlled groundwater levels by lysimeters. Field experiment results indicated that capillary rise had close relationship with the groundwater table depth, soil moisture of 10-40 cm soil layer and leaf area index. These factors have been taken into account to develop the empirical equation for capillary rise simulation. The model parameters for Songnen Plain were derived by Levenberg-Marquardt and global optimization calculating method. The modeled capillary rise has a good agreement with the observed data (r (2) = 0.875). With the simulation model, the critical water table depth was identified as 2.5 m, indicating that soil secondary salinization will not occur when the water table depth is deeper than 2.5 m. Therefore, in the irrigation areas, groundwater table depth should be controlled to be higher than 2.5 m to prevent the occurrence of soil secondary salinization. The results from this research will provide useful information for the water sources management and soil secondary salinization control in Songnen Plain of China, one of the most serious saline-affected areas in the world.