By definition, soil salinization is "the process by which a nonsaline soil becomes saline, as by the irrigation of land with brackish water," according to Dictionary.com. The dissolved salts in irrigation water are the primary source of this problem.
Soil salinization is often a problem in arid regions where ions of soluble salts build up in the soil. In these regions, where irrigation is required for plants to grow, the processes of evaporation and transpiration leave the salts behind in the soil. Over several years, the amount of salt grows to the point that it hinders both seed germination and plant growth, reducing crop yields and eventually rendering soil unusable.
In New South Wales, there is a growing concern that soil salinity is also causing an increase in groundwater salinity. The NSW Government reports that farmers make the problem worse by replacing deep-rooted perennial plants with shallow-rooted crops and pasture cover that require less water. Their shallow root systems allow the salt ions to leak past the root zone into the water table. The government warns that the over-irrigation of crops is adding to the problem. As a result of dryland salinity and irrigation salinity, New South Wales also reports growing problems of urban salinity affecting lawns and gardens of those who dwell in cities.