Dry saline land, often referred to as magnesia land, is where patches become to saline for crop and pasture growth, but this is not caused by a perched water table. The salt is naturally occurring in subsoil clays but finds it way to the surface through the capillary rise of moisture to the surface, particularly after extended drought periods, to eventually become too toxic for plant growth. Once patches bare out, evaporation and salt accumulation increases, and when topsoil erodes exposing clay layers the degradation increases.
Patchy areas can often decrease after periods of heavy rainfall prior to sowing that periodically leaches salts out of surface layers, but they will reappear and can lead to permanently degraded areas over time.