soil salinisation

The accumulation of soluble mineral salts near the surface of soil, usually caused by the capillary flow of water from saline ground water. Where the rate of surface evaporation is high, irrigation can exacerbate the problem by moistening the soil and causing water to be drawn from deeper levels as water evaporates from the surface. The evaporation of pure water leaves the salts behind, allowing them to accumulate, and they can reach concentrations that are toxic to plants, thus sterilising the land.