Impacts of land use and soil depth on soil physicochemical properties and implications for sustainable land management in the Bededo Watershed Northeastern Ethiopia
摘要
Land use conversion from natural vegetation to agricultural and grazing systems accelerates soil fertility decline by depleting soil organic matter, degrading soil structure, reducing porosity, and impairing water-holding capacity, thereby posing serious threats to sustainable land management and ecosystem health. Understanding how a land use and soil depth influence soil property is vital for implementing strategies to curb further degradation. Therefore, this study aims to assess the impact of various land use types; forest, shrub/bush, grazing, and cultivated land and soil depths (0–20 cm and 20–40 cm) on the physicochemical properties of soil in the Bededo Watershed, Northeastern Ethiopia. The findings indicate that soil physicochemical properties differed significantly (P ≤ 0.05) among land-use types and soil depths. Forest soils exhibited the highest silt (35.7%) and clay (48.0%) contents, total porosity (43.3%), soil moisture (26.4%), SOM (1.87%), total N (1.04%), available P (5.51 ppm), CEC (35.1 cmolc kg⁻1), and exchangeable bases, Na (0.72 cmolc kg⁻1), K (1.46 cmolc kg⁻1), Ca (10.63 cmolc kg⁻1), and Mg (7.73 cmolc kg⁻1). In contrast, cultivated soils exhibited the lowest total porosity (29.6%), soil moisture (15.4%), SOM (0.38%), and total N (0.26%). Grazing land soils exhibited the highest sand fraction (56.4%) and bulk density (1.40 g cm⁻3), along with lower pH (5.21), available P (2.49 ppm), CEC (15.3 cmolc kg⁻1), and exchangeable K (0.63 cmolc kg⁻1) and Ca (2.37 cmolc kg⁻1). Correlation analysis of soil properties showed that a decrease in soil organic matter was significantly associated with increased sand content and bulk density, and with reduced clay and silt fractions, soil pH, total N, CEC, and exchangeable Na, and K. The findings indicate that soil degradation in cultivated and grazing lands is evident from substantial reductions in soil organic matter, total nitrogen, available phosphorus, cation exchange capacity, and key nutrients, which threaten long-term nutrient sustainability and agricultural productivity in the watershed. The reviewed literature provides unequivocal evidence that comprehensive land management strategies encompassing balanced fertilizer use, soil amendments, conservation tillage, forest rehabilitation, soil and water conservation, land-use planning, and strong community engagement are fundamental to reversing land degradation, enhancing watershed resilience, and securing sustainable agricultural production. The study recommends that maintaining soil fertility and watershed functionality requires the protection of natural forests, the adoption of sustainable land management practices, comprehensive land-use planning, and active community engagement in understanding and addressing land-use impacts.