Effects of slope gradient and changes in land use/cover on selected soil physico-biochemical properties of the Gerado catchment, north-eastern Ethiopia

Abstract

The study aimed to determine the effects of slope gradient and land use/cover changes on the spatial variability of selected topsoil characteristics, and to assess their value for sustainable soil management. Disturbed and undisturbed samples were taken from the top 20 cm soils of three different slope gradients and four distinctive land use/cover patterns (LULC) of the Gerado catchment, north-eastern Ethiopia. The one-way ANOVA and Pearson correlation coefficients (r) were used to test the significance mean differences of the soils’ physico-biochemical properties (α = 0.05), and to determine their correlation and mutual effects. As the results showed, the contents of sand, silt, clay, field capacity, exchangeable K and Na were significantly different with the change in the slope gradient (p < 0.05). The clay contents demonastrated a significant variation between sloping and steep gradients while exchangeable Na significantly varied between toe slope and steep gradients (p < 0.001). The mean values of clay, exchangeable Na and field capacity varied significantly between the flat and steep slopes (p < 0.001 and p < 0.05, respectively). The soils of flatter slopes had relatively higher soil organic matter (SOM) and clay contents than the steeper slope soils; hence, field capacity was significantly higher. The contents of sand, silt and exchangeable K were significantly different between sloping and steep gradients (p < 0.05). The changes observed in LULC affected the amount of clay, SOM and total nitrogen (TN). The clay contents showed a significant variation (p < 0.05) between cultivated and shrublands while SOM and TN had significantly varied between arable and grassland covers (p < 0.01 and p < 0.05, respectively).

Keywords:

• Gradient variation
• Land use/cover
• Soil properties

Acknowledgements

The authors are extremely grateful for the financial contribution of the Office of Vice President for Graduate Studies and Research (OVPGSR), Addis Ababa University (AAU), Ethiopia. Many thanks as well to the insightful comments of the anonymous reviewers. The authors heartily extend their gratitude to Dr Michael Brett-Crowther, the editor of the journal, for his rapid facilitation of the reviewing and publication of the research article, and timely response to their recurrent requests. We appreciate the contribution made by Lulseged Tamene in reading the manuscript, and Bamlaku Amente with the preparation of the location map of the study area. The authors also thank Dr Diogenes Antille for his help with English in preparing this research article.