Assessment of soil quality along the elevation gradient of the Seti River watershed in Pokhara Metropolitan City, Nepal

Abstract

Soil quality is essential for sustaining agricultural productivity, globally. Hence, this study evaluated the effects of elevation gradients and soil depths on agricultural land quality in the Seti River watershed, Pokhara Metropolitan City (PMC), Nepal. Using a stratified random sampling method, 60 samples were collected across three elevation gradients (500–700 m, 700.1–900 m, 900.1–1100 m) at depths of 0–15 cm and 15–30 cm. The soil quality index (SQI) revealed good soil quality across all elevations, with values of 0.88, 0.86, and 0.82 for lower, mid, and higher elevations, respectively, despite variations in individual nutrient levels. Elevated nitrogen (N) and phosphorus (P) levels highlighted the need for regulated fertilizer application. Kruskal–Wallis test identified significant decreases in soil organic matter (SOM) and soil organic carbon (SOC) with increasing elevation. Depth-wise analysis showed that the potential of hydrogen (pH) in the topsoil (0–15 cm) was nearly neutral, while the subsoil (15–30 cm) exhibited weak acidity. Nutrient concentrations, including N, P, and potassium (K), were significantly higher in the topsoil than in deeper layers, indicating a need for prudent nutrient management to minimize leaching and maintain soil health. Accordingly, PMC soils can be considered favorable for agricultural productivity; however, site-specific management strategies should performed. Reducing excessive fertilizer use in low-elevation areas can prevent nutrient imbalances while monitoring and enhancing SOM in higher elevations through compost or green manure application is recommended. These actions can enhance soil fertility, reduce environmental impacts, and promote agricultural resilience.