CHLORIDE MOVEMENT IN AGGREGATED SILT LOAM SOIL COLUMNS

Studies on salt movement with water in well aggregated fine-textured soils are scarce though fertilizers are also used in these soils for crop production. To gain insight into the process of salt movement in such soils, displacement of surface applied chloride slug with water was studied in aggregates of six size ranges viz., 2.0-4.0 mm, 1.0-2.0 mm, 0.5-1.0 mm, 0.25-0.50 mm, 0.10-0.25 mm and 0.06-0.10 mm and in soil-as such in 30 cm long and 7.2 cm internal diameter glass columns. Maximum chloride concentration occurred at 23 cm depth in columns of 0.25-0.50 mm aggregates after 24 hours of infiltration initiation. The chloride peak tended to be shallower in aggregates smaller than this size group. In aggregates greater than 0.25-0.50 mm size, however, no sharp peak of chloride concentration was observed but it scattered almost uniformly below 8 cm depth. An equation predicting peak of salt concentration in soil-as such does not explain this scatter in aggregated soils. However, when the applied water was apportioned into mobile and immobile phases, the equation predicted scatter of salt concentration in aggregated soil columns to a reasonable accuracy.