Changes in land use and land cover: effects on selected soil properties in Sdeyni Sub-watershed, Northeastern Ethiopia

Abstract

Land use and land cover changes coupled with unplanned agricultural activities have contributed to land degradation. Hence, this study evaluated land use land cover changes, and effects on properties of soils in the Sdeyni sub-watershed in Northeastern Ethiopia. Satellite images for the periods of 1984, 2000, and 2020 were gathered to analyze the land use changes.  Crop land, forest land, and bush-land were selected to determine their effects on soil properties. Eighteen disturbed composite and 18 undisturbed core soil samples were collected from the selected three land use types at two depths replicated three times. The results showed that within 36 years, the overall pattern of forest land declined by 1080.49 ha (10.34%) with an annual rate of 0.028%. The LULC analysis showed that the area of bush-land decreased by 4.27% during the first period (1984-2000), and by 0.91 % during the second period (2000-2020). Significantly large areas in the watershed are devoted for crop category while the smallest portion is covered by settlement part. Contrary to this, an increase in the size of cultivated and settlement lands were detected by 5.1 and 3.6%, respectively, compared to 1984. In all land uses, bulk density increased with depth, where the highest value was obtained in the croplands. Across land uses, soil pH varied from 5.57 to 6.93 and it was found in a moderately acidic soil reaction. Significantly higher contents of organic matter, total Nitrogen, and available Phosphorus were obtained on the surface soil of the forest lands. Exchangeable bases and cation exchange capacity showed significant differences among land use types and soil depths. All the analyzed bases were more concentrated in the subsoil of the forest lands whereas lowest values were observed on the crop lands. Generally, forest land declined, while an increase in the cultivated and settlement lands was the major land use land cover change. Croplands in the watershed were found poor in soil nutrient content. Therefore, immediate policy interventions are required to protect the forest lands and improve sustainable agricultural productivity.