Abstract
The study was conducted at the degraded land soils of the Abuhoy Gara Catchment, which is located in the Gidan District of North Wello Zone, Ethiopia to determine the impact of land use type and soil depth on the distribution of soil physical and chemical properties. Soil samples were collected from representative locations with four replications at two depths, surface (0-15 cm) and subsurface (15-30 cm) of cultivated, grazing and bush land use types. One hundred eighty soil samples were collected from the depths of 0-15 and 15-30 cm each in a radial sampling scheme using an auger. Totally, twelve composite soil samples were collected using flexible grid survey method of 1:30,000 scales. The collected samples were air-dried, homogenized and sieved to pass a 2 mm mesh sieve for the standard physical and chemical analyses. Results showed that the soil physical and chemical properties were significantly affected by the interaction of land uses and soil depths. Silt content decreases while clay content increases across depth from surface to subsurface soils. The lowest pH-H2O was registered at the subsurface soils of the grazing lands, while the highest was recorded at the surface soils of the bush land. The interaction effect of land use by soil depth on the variability of soil organic matter was significantly higher at surface layer of the grazing land and lower at surface layer of cultivated land. Similarly, soil total nitrogen was highest in surface layer of the grazing land, while it was lowest in subsurface layer of the bush land. Exchangeable bases were highest in surface soils of the bush land and lowest in the surface soils of cultivated land. The contents of both exchangeable bases were decreasing with soil depth in all land uses except the bush land. Significant difference in cation exchange capacity contents was observed as highest in surface soil layer of the bush land and lowest in surface soil layer of the cultivated land. From the results of the study, it can be concluded that the interaction of land use with soil depth showed negative effects especially disturbance of soil nutrient status on cultivated land in surface soils. In general, the spatial variability of soil properties indicates the soil conditions were strongly affected by inappropriate land use and soil management practices including soil depth. Therefore, reducing intensity of cultivation, adopting integrated soil fertility management and application of organic fertilizers could maintain the existing soil condition and replenish degraded soil properties.
Highlights
Securing food and a livelihood is inextricably linked to the exploitation of the natural resource base in Ethiopia, where over 85 percent of the population lives in rural areas and contribute significantly to the total export value (Alemneh, 2003)
Each composite sample was made from a pool of fifteen point samples and from the twelve composite soil samples major soil fertility parameters were analyzed
The soil samples collected from representative fields’ were air-dried, mixed well and passed through a 2 mm sieve for the analysis of selected soil physical and chemical properties
Summary
Securing food and a livelihood is inextricably linked to the exploitation of the natural resource base (land, water and forest) in Ethiopia, where over 85 percent of the population lives in rural areas and contribute significantly to the total export value (Alemneh, 2003). As the interaction between natural and anthropogenic management system persists (Assefa and van Keulen, 2009), soil undergoes vertical exchange of materials which in turn resulted in physical and chemical changes from surface soil to sub-soils (Brady and Weil, 1999). Human management system such as frequent plowing and tillage for the purpose of cultivation, grazing or similar uses changes the proportions of many soil properties with changing depths (Ali et al, 1997; MacCarthy et al, 2013). Sheet erosion and intensive leaching process leads to higher concentration of clay content and lesser concentration of calcium, magnesium, potassium and sodium in the subsoil than the topsoil (Adeboye et al, 2011)
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