Assessing the Effects of Soil and Water Conservation Practices on Soil Erosion and Soil Fertility in the Fetam Watershed in the Blue Nile Basin of Ethiopia.

Understanding sustainable land management is important for agricultural production. However, soil fertility has been declining due to anthropogenic and natural factors. To curb these problems, soil and water conservation (SWC) practices have been implemented over the last 15 years in the study watershed, but their impact has not been studied in detail. Therefore, this study was conducted to study the effects of SWC practices on soil fertility and soil erosion in the Fetam watershed. The Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) and sediment delivery ratio (SDR) model were used to analyze the sedimentation based on the required input parameters of the model such as land-use/land-coverraster data, Revised Universal Soil Loss Equation factors such as rainfall-erosivity data, erodobilityfactor, cover factor (C), and management factors (P) and raster digital elevation model including the boundary of the study area in vector form. A total of 32 soil samples (0-20 cm) were collected and disaggregated by landscape position: upper, middle, and downstream. After collecting soil samples, the soil physicochemical properties, such as texture and bulk density (BD), and chemical properties such as (pH), organic carbon (OC), total nitrogen (TN), available phosphorus (AP), exchangeable bases, and cation exchnage capacity (CEC) were analyzed using standard laboratory procedures in the treated (Hunkan) and untreated (Kindikan) subwatersheds. The t-test and analysis of variance (ANOVA) results show that the physical and chemical properties of soil differed significantly between treated and untreated subwatersheds and between upper and lower landscape positions (p < 0.05). The mean soil loss in treated and untreated microwatersheds was 14.43 ± 6.63 and 20.31 ± 10.28 t/ha, respectively. This indicates that the SWC structures implemented in the treated subwatershed contributed to reducing soil erosion rates. The treated watershed and lower landscape position had the highest OC (3.69 ± 0.23) and the lowest BD (1.05 ± 0.01). In contrast, the untreated watershed and upper landscape position had the highest BD (1.21 ± 0.01) and the lowest OC (2.35 ± 0.23). Overall, the soil fertility parameters were most favorable in the treated fields and lower-slope positions, suggesting that SWC measures implemented have significantly improved soil fertility and reduced soil loss. Therefore, it is necessary to scale up the SWC practices to other untreated areas of the watershed in the Blue Nile Basin of Ethiopia to achieve sustainable development.