Gebeyaw Tilahun Yeshaneh
The study was conducted at the Maybar watershed, which is located in the Albuko District of South Wello Zone in the Amhara National Regional State. The aims of the study were to identify the effects of different land uses on the magnitudes and directions of major soil fertility parameters and within and among land use types and soil depths. The results showed that soil organic carbon declined exponentially following deforestation and subsequent conversion to cultivated land. The imbalance in soil organic carbon addition from the crops and loss of soil organic carbon have led to the continuous decline of soil organic carbon in the cultivated land soils by 41.6% and 86.5% as compared to the forest and grazing lands, respectively. Soil texture (sand, silt and clay) and all of the soils chemical properties studied were significantly affected (P ≤ 0.05 and/or P ≤ 0.01) by land use. Furthermore, considering the soil depths, higher mean values of Fe (38.59 mg/kg) were recorded in the surface (0-20 cm) soil layer than in the subsurface (20-40 cm) depth. The results obtained from the study indicated that the direction and magnitude of changes in soil attributes under land uses reflect the long-term impact of human being on the landscape as the consequences of increasing human as well as livestock populations.. All the above values were higher than the critical values of 4.2, 0.2, 0.5 and 1.0mg/kg for Fe, Cu, Zn and Mn, respectively. Also the test analysis showed that the content of Fe, Cu, Zn, Mn and organic matter were significantly higher (P < 0.05) in grazing soils than in forest and cultivated soils, while pH was higher in forest soils. The results of correlation analysis revealed that Cu had significant (P < 0.05) positive correlation with silt content and Fe (r = 0.56* and 0.51*, respectively) but negative and non-significant with clay fraction. Iron and Cu were significant with organic matter (r =0.55* and 0.89**, respectively). The manner in which soils are managed has a major impact on agricultural productivity and its sustainability. Therefore, strategies to feed the expanding population in the country have to seek a sustainable solution that better addresses soil fertility management.
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