Salt accumulation in sandy soils after the clearance of the native vegetation in Phra Yun, Khon Kaen was investigated in order to clarify the process of salinization and to identify methods of control.
Deforestation changes the balance between rainfall and evapotranspiration, resulting in the increase of percolation and seepage water. Saline seepage water induces salinization in the foot slopes and the low-lying lands.
Salt-affected soils displayed mottlings in the upper part of the profile in connection with the elevation of the groundwater table in the rainy season. In these soils, salt reached the surface through the upward movement of saline water mainly at the beginning of the dry season. Salt could also be easily leached out to the subsoil with rainwater.
Accumulation of salt on the soil surface in the dry season was associated with the elevation of the groundwater table to a critical level at the end of the rainy season and continuity of capillary pores above the groundwater level.
To control salt accumulation, the planting of eucalyptus trees which led to the lowering of the groundwater table was found to be effective in preventing saline seepage water from reaching the low-lying lands.