Soil salinity sodicity and irrigation water quality in the Ethiopian Main Rift Valley and implications for sustainable management

Soil salinity and sodicity are major constraints to sustainable agriculture in semi-arid regions, particularly in Ethiopia’s Main Rift Valley. Increasing salt accumulation in soils and irrigation water threatens crop water productivity, soil health, and the long-term sustainability of irrigated systems. This study assessed soil salinity and sodicity, evaluated irrigation water quality, and identified management strategies for salt-affected agroecosystems. Field investigations were conducted in Kewet and Efratana Gidim districts, where 30 soil and six irrigation water samples were collected from representative landforms, including alluvial plains, river terraces, and micro-depressions influenced by hot springs. Soil properties, electrical conductivity (ECe), sodium adsorption ratio (SAR), and residual sodium carbonate (RSC) were analyzed. Results showed that a substantial proportion of sampled soils exhibited moderate to high salinity and sodicity levels, indicating significant degradation risks under current irrigation practices. Clay-rich Vertisols and Fluvisols dominated the area, with high cation exchange capacity, shrink–swell behavior, and slickensides that enhance salt retention and restrict infiltration. Salt concentrations increased with depth, with sodium and sulfate predominating, suggesting vertical redistribution under irrigation and episodic flooding. Irrigation water, particularly from Kora Spring, showed elevated SAR and RSC, increasing sodicity risks and reducing root-zone water availability. Integrated management strategies, including optimized irrigation scheduling, periodic leaching, improved drainage, soil amendments, and salt-tolerant crops, are essential to sustain productivity. These findings provide practical guidance for salinity management and contribute to understanding soil–water–climate interactions in salt-affected agroecosystems.