Impacts of Irrigation on Soil Characteristics in Selected Irrigation Schemes in the Upper Blue Nile Basin

Abstract

Assessing soil and water qualities for salinity and other related problems and suggesting remedies are fundamental in irrigation management decision options. The analysis reported in this chapter provides the necessary information to predict the soil and water related problems as consequences of irrigation practices undertaken at various irrigated command areas in the upper Blue Nile River basin, Ethiopia. The study presented in this chapter was conducted in five selected irrigation schemes which have been constructed before 20 years in the Upper Blue Nile basin, Ethiopia. Farmers' perception of changes in crop yield as a result of changes in soil characteristics and water logging problems were compared with soil physical and chemical analyses. Soil profile pits were opened from selected representative sites in the respective irrigation command areas and from non-irrigated fields adjacent to the irrigated area for the purpose of comparison. The soil pH at Mendel and Tikurit schemes ranges mildly alkaline to moderately alkaline in both irrigated and non-irrigated sites and pH increased with depth due to the corresponding increase in bicarbonate. Infiltration rate and bulk densities in all schemes showed some variation between irrigated and non-irrigated sites. Farmers perceive changes in land productivity as a result of irrigation activities compared with non-irrigated plots especially, onion crops decreased from time to time. Furthermore, seasonal water logging was observed in some of the schemes during the rainy season as a result of flat topography and vertic nature of the soils of the command area. Total nitrogen, organic carbon and to some extent available phosphorus contents are generally found to be in the range of low to very low status while potassium is found to be more or less enough for the current low yield levels.