A form of desertification on irrigated lands is called salinisation and alkalinization of soils. This is due to inadequate leaching of salts contained in the soil or added in irrigation water. Salinisation and waterlogging commonly occur together. Where the soil is waterlogged, the upward movement of saline groundwater leaves salts on the surface where water evaporates.

Worst affected regions

On soils that are not waterlogged, salinisation can still occur when water containing soluble salts moves from irrigation furrows into the ridges where crops are planted or to high spots in poorly levelled land. Under-irrigation of weakly permeable soils can also lead to salinisation if the irrigation water is salty.

Between 600 and 2000 million square kilometres of irrigated land are affected by salinisation waterlogging or alkalinisation