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.