Saline and saline-sodic of the middle awash valley of Ethiopia

There is a growing concern among soil scientists, agriculturalists, environmentalists and policy-makers on salinization of the irrigated lands of the Middle Awash Valley. Over 2000 ha of irrigated cotton and banana fields have been abandoned due to salinity build up. Therefore, the objective of this work was to identify the extent, nature and distribution of salt-affected soils. the investigation was based on soil and water sampling and laboratory analysis. About 43 percent were classified as non-saline, 40 percent saline, 16.98 percent saline-sodic and 0.02 percent sodic. Electrical conductivity (ECe) of the 0-30 cm soil depth of the saline soil varied from 4 to 110 dS/m and was from 4 to 77.6 dS/m in the saline-sodic soils. Sodium, calcium and chloride were strongly correlated with ECe in saline-sodic soils but not as strongly as that of soluble calcium and chloride in slaine soils. All soil/water aqueous extracts showed strong correlation to saturation paste extracts (ECe). However, the pH of woil/water suspension did not correlate at all with pHe. The soluble sodium content reached 473.5 me/1 and was largely concentrated in the 0.30 cm horizon of the saline-sodic soils and this was supported by the high exchangeable sodium percentage (ESP). In contrast, a maximum soluble calcium value of 590 me/1 highest chloride concentration of 1040 me/1 and 759 me/1 was found in the 0-30 cm depth of the saline and saline-sodic soils respectively. Sulphate was the second highly con. anion while the, carbonate concentration was nil to trace in both soil types. In most of the irrigated fields of the Middle Awash Valley, the main source of salinity is shallow water table. The salinity of the bore holes varied for 0.9-67-7 dS/m. Salinity was high on the upper 120 cm soil depth were the ground water depth was above 2.6m. On the other hand, high reducation of seed cotton yield was obtained when salinity on the top 120 soil depth wa may be above but not certainly below 4 dS/m. Finally the salt-affected soils in the Middle Awash Valley could be grouped into saline and saline-sodic soils.