Effects of Salinity and Sodicity of Water and Soil Texture on Some Soil Mechanical Properties and Optimum Water Content for Tillage

In many arid and semi-arid countries, population growth and the need for increased food production are forcing the management planners to consider all sources of water to achieve further development. Water quality could affect soil physical, chemical, and biological properties. A laboratory experiment was carried out to study the effect of soil texture and salinity and sodicity of water on some physical and mechanical properties of the soil. Two soils with sandy loam and clay loam textures were treated with twelve waters with different qualities, i.e. combinations of four levels of salinity (EC) including 0.2, 1, 6, and 10 dS m-1 and three levels of sodicity (SARs of 1, 5, and 12), and were subjected to wetting and drying for five times. The consistency limits, plastic and friability indices, dispersible clay and optimum water content in Proctor compaction test were determined. The significant effects of treatments on the determined soil properties suggested that water quality altered the soil microstructure. Effects of salinity and sodicity on clay loam soil were more than sandy loam soil. Unlike the clay loam soil, in the sandy loam soil, the consistency limits did not significantly change as a result of low clay content. At each salinity treatment, the higher the SAR of water, the greater was the impact on soil microstructure; as the plasticity index was increased and friability index was decreased, both might result in undesirable tillage operations. Increase in the calcium concentration at each SAR treatment reduced the dispersible clay and increased Proctor test optimum water content.