Assessing the Impact of Soil Erosion and Nutrient Loss under Different Land Uses in Fragile Agro-Ecosystems of Rukiga District in Uganda

Abstract

Soil erosion poses a major threat to soil fertility and agricultural productivity in fragile agro-ecosystems of Sub-Saharan Africa, particularly on steep cultivated hillsides. In Rwamucucu Subcounty, Rukiga District, Uganda, unsustainable land use and rudimentary farming practices accelerate soil and nutrient losses, undermining crop production. This study aimed to quantify soil and associated nutrient losses under different land uses and soil management practices in erosion-prone areas. An experimental design using 4 × 2 m runoff plots was employed during the rainy season for four consecutive weeks across selected land use categories: terracing, contour cropping, no soil conservation practice, eucalyptus plantation, and natural grass cover. Eroded sediments were collected and analysed for key physico-chemical properties using standard laboratory procedures. Results showed significant variation (p < 0.05) in soil loss among land uses and management practices. Eucalyptus plantations recorded the highest soil loss (484.5 ± 43.8 kg/ha), followed by crop fields without conservation practices (beans (366.1 ± 25.7 kg/ha), bananas (371.3 ± 24.6 kg/ha), and potatoes (342.0 ± 17.83 kg/ha). Contour cropping moderately reduced soil loss, while terracing further lowered erosion, with banana fields under terracing recording 218.3 ± 24.8 kg/ha. Natural grass cover exhibited the least soil loss (116.05 ± 15.32 kg/ha). Substantial losses of soil organic matter and essential nutrients, nitrogen, available phosphorus, potassium, and magnesium were observed across all treatments, with the highest percentage losses generally occurring under no conservation practice and eucalyptus plantations. For example, available phosphorus loss reached up to 99.15 ± 0.26 kg/ha under eucalyptus, while exchangeable potassium losses exceeded 99% in some non-conserved crop fields. Potato-grown fields consistently exhibited higher nutrient losses compared to beans and bananas. These findings demonstrate that soil erosion significantly depletes soil fertility, particularly under poor land management and certain plantation systems. The study shows the critical importance of adopting effective soil conservation measures, such as terracing and contour cropping, to reduce erosion, enhance nutrient retention, and promote sustainable agricultural productivity in erosion-prone highland landscapes.