APPRAISAL AND MAPPING OF SOIL SALINITY PROBLEM IN AMIBARA IRRIGATION FARMS, MIDDLE AWASH BASIN, ETHIOPIA

One of the main reason for the loss of productive land in irrigated fields is the buildup of salinity in the soil. In Amibara irrigation Scheme, though no systematic appraisal and mapping has been made before, large tract of land has been abandoned because of salinity problem. Hence a study was conducted to appraise the salinity problem of the Amibara irrigation farms in Middle Awash Basin and to generate thematic maps using Arc GIS for further management recommendation. A total of 249 surface soil samples representing 15,256.22 ha Amibara Irrigation farms were collected and analyzed. Standard methods were followed to measure pH, electrical conductivity (EC) and soluble cations. Arc GIS 9.3 was used to map the overall salinity and sodicity problem of the area. Results showed that around 34 % (5239.79 ha) of the command area has been mapped as saline soil (ECe > 4 dS/m and SAR 4 dS/m, and SAR >13). From the thematic maps generated, it is concluded that proportion of the land taken up by salinity is rapidly increasing. More and more land is fully abandoned due to salinity problem. The water table control by rehabilitating the subsurface drainage system seems to be the only feasible way to improve sustainability of the scheme.