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Understanding soil types of a given area is an important prerequisite to design optimum management strategies such as irrigation water management. The study was thus conducted on characterization and classification of Zamra irrigation scheme in Abergelle district of Amhara Region, which has an area of 196.16 ha. For this study, 53 auger observations, four profile pits, extensive visual observations, reconnaissance survey, and descriptions of soil profiles and laboratory analysis were used to study the morphological and physicochemical properties of the soils of the scheme. Twelve disturbed and undisturbed soil samples were collected from all profiles of each genetic horizon for laboratory analysis. The soils of the study area were identified based on Food and Agricultural Organization of the United Nations/World Reference Base for Soil Resources (FAO/WRB) 2015. The results revealed that the textural classes of all profiles of the study site ranged from sandy clay loam to sandy loam. The chemical properties of the soil in terms of total nitrogen, organic matter, and available phosphorus were in the very low and low categories as per the criteria developed by Tekalign and Olsen, respectively, whereas exchangeable bases (Ca, Mg, K, and Na), cation exchange capacity, and extractable micronutrients (Fe, Mn, Zn, and Cu) were medium to high. Based on morphological, physical, and chemical analyses, the soils were classified as Leptic Regosols (Eutric, Loamic; 21.99% of the area), Vertic Cambisols (Hypereutric; 17.87%), Haplic Regosols (Eutric; 36.69%), and Rhodic Nitisols (Eutric; 23.44%). Therefore, management techniques that enhance soil fertility (including crop rotations, manuring, fallow periods, proper management of crop residues, and leguminous cover crops) and water-saving technologies suitable to the terrain of the area are the best options to enhance land productivity in the area.

Erosion map of a watershed offers a wealth of knowledge and can be crucial for implementing site-specific management interventions. Thus, watershed-based soil erosion assessment was conducted to recognize erosion hotspot areas, while aiming to roughly calculate the average annual soil loss in Genda-wuha watershed, with a total area of 154,548.5 ha located in the northwest lowland of Blue Nile basin Ethiopia using USLE/GIS approach. Sixteen years of rainfall data, 53 soil sample data, a 30m by 30m digital elevation model (DEM), a land-use/land-cover map, and support practice factor were used to determine high erosion risk areas. The USLE parameters were integrated and analyzed using a raster calculator in the ArcGIS platform to predict and map the mean annual soil loss of Genda-wuha watershed. The result showed that the annual soil loss of the watershed extends from none in the lower and middle part of the watershed to 75.36 Megagram (Mg) ha-1yr-1 in the steeper parts of the watershed with a mean annual soil loss of 7.9 Mg ha-1yr-1. Most of the soil erosion affected areas are spatially situated in the upper steep slope parts of Genda-wuha watershed, which could be as a result of an increased slope gradient and length in the specified location. However, the majority of the watershed (82.62%) was estimated to be low erosion rates varying from 0 to 5 Mg ha–1 yr–1 and these areas correspond primarily to nearly flat landscapes of the watershed.

Soil and water conservation (SWC) interventions are needed to control rainfall-driven erosion, and profitability of SWC measures at the sub-catchment scale emerges as the principal reason for their adoption. This study carried out a cost–benefit analysis of SWC measures in mountainous agricultural catchments. Physical data were obtained through field measurements of discharge, sediment and nutrient loss at the sub-catchment scale with and without SWC measures. The major cost benefits of various measures implemented in the study area were quantified using net present value (NPV), and direct market prices were employed in valuing the cost of items required for crop production. The results revealed that sediment loss decreased by 8.78 Mg ha−1 y−1 (46.8%) due to SWC measures, and the cost of production inputs, such as fertilizer (urea) and lime, was reduced by $17.97 ha−1 y−1 and $3.63 ha−1 y−1, respectively. Furthermore, crop yield was enhanced by 13% for teff, 19.4% for sorghum and 19.42% for chickpeas, which is equivalent to economic returns of $102, $96.9 and $140.25 ha−1 y−1, respectively. The total discounted cost of SWC interventions was about $331.74. This includes establishment costs, maintenance costs, input costs and the costs resulting from lost productive land. In sum, the total discounted benefits of SWC measures were the enhancement of crop production, a reduction in lime requirement and a reduction in the loss of total nitrogen and sediment, estimated at about $809.42. Hence, it is possible to deduce that SWC measures reduced nutrient depletion and greatly improved crop yield with a NPV of $477.68 ha−1. The results strongly suggest that SWC measures in the study sub-catchment, as well as in nearby areas with a similar indigenous SWC adoption strategy, topographic conditions and agroclimatic characteristics, should be maintained.