Effect of clay interlayers on soil water-salt movement in easily-salinized regions

Large-scale soil column experiments for simulation water-salt movement in clay interlayers under normal growing conditions were carried out in an easily-salinized region for different textures of soils and groundwater condidons in the Huang-Huai-Hai alluvial plain of China.In this study,the 20-year measurement was analyzed to examine the effect of clay interlayers on soil water-salt movement in easily-salinized regions.Results show that the clay interlayer has a significant positive effect on the water-holding capacity in the soil and acts as a filter obstructing the salinity infiltration.This is especially true for restraining the penetration of surface accumulated salts.The thicker the clay interlayer is,the greater the effect will he.The range of depth to groundwater is likely to he smaller in the area with surface accumulated salts and clay interlayers around 1.0 m than that with silt loam soils around 1.5 m.And in the latter case,the salinization of soils is easily induced when the groundwater level is lower than a threshold value of 2.5 m.The amount of accumulated salts is found to be higher in clay interlayers than that in silt loam soils.Thus, proper monitoring and measures are necessary to prevent the secondary salinization of soils in the practice of water resources management.