Laboratory investigation on reclamation of a saline-sodic soil by column leaching experiments

Soluble salts and sodium are the main problems of the soils in arid and semi-arid regions. Application of organic and mineral conditioners is a basic strategy to accelerate the leaching and reclamation of these soils. This study was conducted to evaluate the efficiency of organic matter and gypsum in the reclamation of a saline and sodic soil using leaching columns. Soil sample was selected from abandoned agricultural lands in the western edge of Urmia lake. Soil leaching was conducted continuously based on the pore volume. The cations, electrical conductivity and sodium adsorption ratio in each pore volume of drain water were measured. In addition, these parameters were determined after the completion of leaching throughout leaching columns. The results indicated that in the control treatment, leaching couldn’t be continued for more than two pore volumes which may be attributed to effect of the high exchangeable sodium on destruction of soil structure and blocking of the soil pores. The sodium adsorption ratio of soil sample after leaching in gypsum and gypsum with organic matter treatments, decreased from 62.5 (meql-1)0.5 to 1.08 and 1.51 (meql-1)0.5, respectively, which reflects the effectiveness of gypsum and organic materials in sodic soil reclamation. The organic matter treatment also decreased the sodium adsorption ratio by 85 percent which may be related to the release of calcium from the lime in the soil and replacing of the exchangeable sodium. After leaching, the electrical conductivity of the soil samples was below the critical level, 4 dSm-1, regardless of the applied treatment type which represents the leaching efficiency to remove soluble salts from the soil profile. In general, application of the gypsum, equal to gypsum requirement, and organic matter in the leaching process, is recommended for effective reclamation of soils in the study area.