Soil Salinisation in Irrigated Drylands of the Middle East and North Africa: Drivers, Extent, Crop Impacts and Reclamation Strategies

Salt-affected soils cover an estimated 8–12 million km² worldwide, and secondary salinisation caused by irrigation threatens a large share of the irrigated land on which food security in the Middle East and North Africa (MENA) depends. This review synthesises evidence on the processes, extent, agronomic impacts, economic costs and management of soil salinity, with emphasis on Egypt and the wider MENA region. The main drivers are high evaporative demand, shallow saline water tables resulting from inadequate drainage, the use of saline or reused drainage water for irrigation, seawater intrusion in coastal deltas and, increasingly, climate change. Salt reduces crop yields once soil salinity exceeds crop-specific thresholds, ranging from about 1 dS/m for beans to about 8 dS/m for barley, with globally estimated losses of the order of tens of billions of US dollars per year. Remote sensing and machine-learning approaches now allow salinity to be mapped and projected at continental scale, and suggest that salinity in many drylands will increase under climate change. Effective responses combine drainage, leaching with good-quality water, gypsum for sodic soils, precision irrigation, salt-tolerant crops and halophytes, and policies that link the reuse of drainage water to soil monitoring. The review argues that salinity management must be integrated with water-reuse and coastal-adaptation strategies, which in Egypt are expanding rapidly.