Column leaching experiments on saline soils of different textures in Sistan plain

Salinization is the main characteristic of soils in arid and semi-arid regions which reduce the agricultural potential of irrigated lands. Therefore, soil reclamation as well as determination of the leaching requirement for salt control is very important for better plant growth. In this study, the effects of leaching on saline soils of Sistan region, southeast of Iran were examined using unsaturated disturbed soil columns. The experiment was conducted on four texture types (loam, sandy clay loam, sandy loam and clay loam) and three replications. Soil samples were purred in polyvinyl chloride (PVC) cylinders and leaching procedures were conducted in 10 stages with up to 5 pore volumes. Effluent from each column was collected and evaluated in terms of Na, K, Ca2, Mg2 and EC. At the end of the study, soil columns were cut and their corresponding samples were analyzed for Na, K, Ca2, Mg2 and EC. The results of leaching experiments showed that the water used in this study could reduce solute concentration and thus, this soil does not need any amendment. For most soil textures, it was also observed that almost 85% of the salts were leached after the fifth stage of the leaching process. According to the results, ions entry into the effluent solution is fast in the coarse textured soils. So, the difference between the amounts of irrigation water needed to transport the salts and leach the saline soils can be attributed to the soil texture. It seems that the main reason for these reactions is the cation exchange.