Assessment of Soil Fertility Variation in Different Land Uses and Management Practices in Maybar Watershed, South Wollo Zone, North Ethiopia

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), water retention at field capacity and permanent wilting point and all of the soils chemical properties studied were significantly affected (P ≤ 0.05 and/or P ≤ 0.01) by land use. Generally, comparisons between the crop fields that have been prolongly cultivated on one hand and the forest and grazing lands on the other revealed a highly significant difference on major soil fertility parameters. For instance, the highest average mean values of exchangeable Ca (10.75 cmol(+)/kg), exchangeable Mg (5.02 cmol(+)/kg) and CEC (28.17 cmol(+)/kg) were observed under the forest land as compared to the lowest values (3.96, 0.81 and 11.83 cmol(+)/kg), respectively, in the cultivated land. Furthermore, considering the soil depths, higher mean values of total N (0.153%), exchangeable Ca (7.71 cmol(+)/kg), base saturation (58.11%) and 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. The cumulative values of land use changes without proper management were negative. The manner in which soils are managed has a major impact on agricultural productivity and its sustainability. In order to be sustainable, development must not be only economically sustainable but also socially acceptable and environmentally sound. Therefore, strategies to feed the expanding population in the country have to seek a sustainable solution that better addresses soil fertility management.