How can irrigation cause salt to build up in dryland soils?

In dryland ecosystems, irrigation can lead to a significant buildup of salt in the soil through a process driven by evaporation and the natural mineral content of water.12

Unlike rainwater, which is essentially distilled through evaporation, irrigation water is typically sourced from surface runoff or groundwater that has collected dissolved minerals and salts from the earth. When this water is applied to crops, the plants and the sun cause the water to evaporate or transpire, but the dissolved salts remain behind in the soil.3214

In arid regions, where natural rainfall is insufficient to flush these salts downward through the soil profile, the concentration of salt increases over time. If the soil has poor drainage, this accumulation is further exacerbated by rising saline groundwater. Without adequate management—such as leaching the soil with excess water or improving drainage—this process can eventually render the land unproductive, turning fertile fields into barren salt flats.324