Assessing the Impacts of Soil Water Conservation Activities and Slope Position on the Soil Properties of the Gelda Watershed, Northwest Ethiopia

Abstract

Soil erosion debilitates soil fertility and agricultural productivity in Ethiopia. Soil and water conservation (SWC) measures have been implemented to address this issue, but their effects have not been evaluated in different parts of the country. This study was therefore conducted to evaluate the effects of SWC structures and slope position on soil properties in the Gelda watershed, northwestern Ethiopia. Core and disturbed composite soil samples were collected at a depth of 0–20 cm from the upper (15–20%), middle (10–15%), and lower (4–10%) slope positions of cultivated fields treated with soil bund (SB), stone-faced soil bund (SFSB), and stone-faced soil bund stabilized by Sesbania sesban (SFSBS) and from untreated fields (control). The samples were analyzed by soil analytical techniques. The results revealed that the clay particles, pH, soil organic matter (SOM), total nitrogen (TN), available phosphorus (AvP), cation-exchange capacity (CEC), and exchangeable Ca2+, Mg2+, and K+ were significantly (p<0.05) increased, while bulk density (BD) and the sand fractions decreased in SWC-treated plots. On the lower slope, significantly higher (p<0.05) clay, silt, pH, SOM, TN, AvP, CEC, and exchangeable bases were recorded, while the upper slope had the highest sand and BD values. The interactions of slope and SWC structures affected the distribution of sand, TN, AvP, exchangeable Ca2+, and Mg2+. The SWC structures implemented in the watershed improved soil fertility, but the impact was stronger when stone-faced soil bunds were integrated with Sesbania sesban plant species. Therefore, during the implementation of SWC structures, the integration of soil physical structures with plant species aligned with slope positions should be considered, as both factors have an impact on soil fertility improvement and soil erosion in the study area and similar agroecologies. The impacts of SWC structures on crop yield, their economic implications, and environmental benefits for the studied watershed and for the region as a whole need further investigation.