Remediation of saline soils by a two-step process: Washing and amendment with sludge

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Soil salinization is a serious land-degradation problem that affects soil, plants and groundwater within ecosystems. In this work, the effect of washing saline–sodic soils with CaCl2 at 2% (w/v) and amendment with composted and dry sewage sludge was evaluated in a remediation assay. The effectiveness of amendments to improve the soil fertility was investigated with seed germination assays of Raphanus sativus L. Two different organic wastes were used: sewage sludge composted with pruning wastes (CP) and thermally dried sewage sludge (T) at rates of 1 and 2% (w/v) on organic matter basis. In general, there was an increase of germination percentage in the amended washed soils. The best indices were obtained at the 1% amendment dose with CP. The low exchangeable sodium percentage (ESP) in washed–amended soil (3 to 6 times lower than that of saline–sodic soil) could partially explain the increase in seed germination percentage of R. sativus L. The incorporation of organic amendments to washed soil also seemed to be beneficial as a step in the restoration process according to the chemical characteristics, especially by increasing the level of nutrients such as carbon, nitrogen, and phosphorus. A significant multiple linear regression of radish germination index in terms of pH values, sodium adsorption ratio of soil (SAR), and different forms of nitrogen (NH4+ and NO2−) was found.Overall, saline–sodic soil washing with CaCl2 followed by addition of organic amendments seems to be a promising strategy for restoration of such soils with simultaneous improvements of cation balance and nutrient/organic matter contents.