Characterization of salt affected soils and identification of salinity sources in irrigated soils: the case of small scale irrigation schemes in Adami Tulu Jido Kombolcha and Ziway Dugda Districts in the Central Rift Valley of Ethiopia

Abstract

Soil salinity is an environmental threat that impedes productivity of crops particularly in arid and semi-arid areas. This research aimed to assess the status, causes, effects and ameliorative measures of soil salinity in irrigated fields in Central Rift Valley of Ethiopia. A total of 40 composite soil samples were collected from groundwater and river irrigated farm plots and corresponding rain-fed plots, and analyzed for pH, EC, TDS, CEC, ESP, Exchangeable Na, bicarbonate, and sum of anions. Similarly, a total of 12 composite water samples from the groundwater and rivers were collected and analyzed for pH, EC, TDS, Na, K, Ca, Ma, Cl, B, SO₄ and CO₃. In addition, focus group discussion and interviews were conducted with irrigation user farmers. The result showed that farm plots irrigated with groundwater from sodic soil environment with Exchangeable Sodium Percentage (ESP) >15 and areas irrigated with Bulbula River are  becoming sodic with an average ESP value of 13.5. Irrigation user farmers who participated in the social survey indicated that soil salinity-sodicity adversely affected growth of vegetables, land productivity and household economy. The social survey also indicated that farmers lack knowledge, skills and capital to apply various ameliorative measures of soil salinity and sodicity. This requires monitoring of irrigation water, planting salt tolerant crops, designing environmentally friendly irrigation practices and empowering
farmers on farming practices in order to mitigate and ameliorate soil salinitysodicity problems, and to enhance sustainability of  irrigation farming in the study areas.