Salt-affected soils as an emerging threat for sustainable land management in Raya Kobo Valley, Ethiopia

Soil salinity and sodicity pose a significant challenge to sustainable land management in Ethiopia’s arid and semi-arid irrigated regions, affecting vast areas of agricultural land. In the Abuarie-Addisalem irrigation scheme of Raya Kobo Valley, productive farmland has become nonviable due to increasing soil salinization and sodicity. Despite the broader issue of salinization in the Raya Kobo valley, a comprehensive analysis of the associated soil properties has been lacking, and thematic mapping has not been adequately conducted. This study was undertaken to characterize the salinity and sodicity levels in the Abuarie-Addisalem irrigation scheme and to generate thematic maps using Geographic Information System (GIS) for sustainable management strategies. A total of 24 soil samples from four profile pits (0–30, 30–60, 60–90, 90–120, 120–150, and 150–180 cm) and 64 surface soil samples (0–30 cm) were systematically collected to cover 762.13 ha of irrigated land. Soil pH and electrical conductivity (EC) were determined from 1:2.5 soil-to-water suspensions and saturated paste extracts, respectively, while concentrations of sodium (Na⁺), calcium (Ca²⁺), and magnesium (Mg²⁺) were quantified using flame photometry and atomic absorption spectrophotometry following ammonium acetate extraction. ArcGIS 10.8.2 was employed to map soil salinity and sodicity across the study area. Inverse Distance Weighting (IDW) interpolation was used to generate spatial distribution maps. The results indicated that 85.31% (650.22 ha) of the irrigated land was classified as non-saline, non-sodic soil, indicating minimal risk and suitability for normal agricultural production. On the other hand, 11.37% (86.69 ha) was classified as saline soil. Furthermore, 2.61% (19.92 ha) and 0.70% (5.31 ha) of the command area were classified as saline-sodic and transitional to sodic soils, respectively. Salt-affected soils exhibited high spatial heterogeneity, occurring in lower landscape positions, depressions, poorly drained flat areas, and areas with shallow water tables, resulting in limited leaching and strong evaporation. These findings expose the emerging extent of salinity-related soil degradation within the irrigation scheme. To remediate salinity and protect agricultural productivity sustainably, measures like planting salt-tolerant crops, reducing salt accumulation, and controlled irrigation should be applied. Periodic soil testing and use of machine learning and remote sensing could be viable option for monitoring seasonal and multi-year salinity and sodicity.