Patterns of Nutrients Cycling and Soil Quality under Different Soil Conservation Practices: The Case of Amalake Watershed, Gidabo Sub-basin, South Ethiopia

Abstract

Soil conservation practices have varying long-term effects on soil quality and nutrient cycling, making it essential to identify the most effective, ecology-specific methods. This study in the Amalake watershed, Gidabo sub-basin, investigated the long-term impacts of different conservation practices: soil bund (SB), micro-basin (MB), fanya-juu (FJ), and a control sample (CS) on soil quality indicators. Bulk soil samples were analyzed for physicochemical properties using standard methods. Principal component analysis (PCA) identified key indicators bulk density (BD), pH, water-stable aggregates (WSA), moisture content (MC), soil organic matter (SOM), and cation exchange capacity (CEC) — to calculate a soil quality index (SQI). All three soil conservation practices significantly (p < 0.01) improved properties such as BD, pH, WSA, MC, SOM, and CEC. The most effective practice, SB, resulted in changes of 28.57% (BD), 74.35% (WSA), 14.48% (MC), 21.05% (CEC), and 100% (SOM) compared to the control. SB also significantly increased the contents of Ca2+ (50.41%), Mg2+ (36.55%), and K+ (100%). However, the impacts on micronutrients were inconsistent. Additionally, SB yielded the highest SQI values across upper (0.68), middle (0.54), and lower (0.86) slopes. Overall improvements in soil indicators followed the order: SB > MB > FJ. Therefore, SB is the most effective soil conservation practice for enhancing nutrient cycling and soil quality in steep, variable landscapes like the Amalake watershed.