The term sodic refers to a soil that has been affected by high concentrations of salt and sodium. Sodic soils are relatively low in soluble salts but are high in exchangeable sodium. saline, sodic and saline-sodic soils are terms used to define arbitrary limits of salt content and exchangeable sodium percentage in salt-affected soils. Sodic soils with low soluble salts but high exchangeable sodium tend to remain in dispersed condition, almost impermeable to both rain and irrigation water. They are of poor tilth - plastic and sticky when wet and prone to form hard clods and crust upon drying. When wet they have a characteristic smooth, slick look caused by the dispersed condition of clay and humus. Sodic soils are very poor for the growth of plants. Exchangeable sodium exceeds 15% of the cation exchange capacity.