Ethiopia faces high risk of soil carbon depletion for nearly half of its total land mass largely due to forest clearing and continuous cultivation. Conversion of natural ecosystems to cultivated agriculture resulted in losses of between 20 and 50% of the soil C stocks in the first meter of the soil depth. Dry Afromontane forests of northern Ethiopia have faced vast exploitation, and almost all these forests have been converted to agricultural lands affecting the functionality and stability of agroecosystem. Here, we studied the effect of land use-land cover changes on soil organic C, total N, and soil C sequestration. Specifically, (a) we characterized major soils of the Desa'a Dry Afromontane forest, northern Ethiopia, and (b) we analyzed the organic C and total N contents of soils with varying land use-land cover types of the Desa'a Dry Afromontane forest. Results show that soil organic C (1.9%) and total N (0.3%) were higher for the middle landscape position than that observed for the upper and lower landscape positions. Soil organic C that ranged from 1.2 in farmland to 2.3% in dense forest also varied with land use-land cover types. Concentration of soil organic C was different among dense forest (2.3%), open forest (1.7%), grazing land (1.6%), and farmland (1.2%). Due to the effect of land use-land cover types, soil total N varied from 0.2% in the farmland to 0.3% in the dense forest. The soil organic C and total nitrogen of the top and lower layer soils were 2.0 and 1.5 and 0.2 and 0.3%, respectively. The soil organic C sequestration for dense forest was significantly higher (48.5 t ha ) than the lower soil layer. Thus, the top soil layers of dense forest at the middle landscape positions stored significant amount of soil organic carbon.

This study investigated the concurrent accumulation of eight heavy metals by two floating aquatic macrophytes (Lemna minor and Azolla filiculoides) cultivated in ambient media and blended wastewaters in the semiarid regions of Ethiopia. Both species accumulated heavy metals in varying degrees with a significant concentration gradient within the immediate water media. Highest bioconcentration factor (BCF) was determined for Mn and Fe in both plants. Results revealed that L. minor was high phytoaccumulator for Fe, Mn, Zn, and Co but moderate for Cd, Cu, Ni, and Cr. On the other hand, A. filiculoides was a high accumulator for Fe, Mn, Zn, and Cu, but its potency was moderate for Co, Cr, and Ni, but lower for Cd. Both species exhibited significant difference in accumulating Co, Zn, and Mn (p < 0.05). In general, the BCFs for both plants were comparable within the same treatment. In this study, stronger associations between the heavy metal concentrations in the plant tissues and in the grown water media were observed for A. filiculoides.

Soil erosion in Ethiopian highlands has caused land deterioration due to moving nutrient-rich top soil to downstream reservoirs while leaving reservoirs dysfunctional due to sedimentation. Micro-watershed management by removing reservoir sediments and using them for reclaiming farmland, while using reservoir water for irrigation, can be a potential solution to simultaneously address soil and water constraints and food security challenges. Still, there is knowledge gap before such a solution can be practically applied. The objective of this paper is to present potential solutions for the reservoir sedimentation problem and specifically highlight the utility of bathymetric survey using an echo-sounder to assess sediment volume. Our results indicated that the estimated reservoir sediment volume was 6400 m 3 leading to a reclamation of 3.2 hectares by layering 0.2 m sediment. The sediment used for reclamation depicts neutral pH (7.3), high organic carbon (2.5%), available phosphorus (9.2 mg/kg) and exchangeable potassium (25 cmol(+)/kg). Garlic (Allium sativum) was planted in the reclaiming abandoned farmland and produced 7.1 t/ha of bulb on average. There is a potential of producing 2-3 horticultural crops per year. Thus, developing methods for scaling up potential farmland reclamation using reservoir sediment would contribute to degraded farmland restoration and food security in Ethiopia and beyond.

Rhamnus prinoide (Gesho) intercropping is a common practice with significant socioeconomic and ecological importance in Ganta-afoshum district. However, this practice is not well explored so far, especially from the perspective of its impact on sustainable land management while land degradation and low productivity is a challenge in the district. The objective of this study was to examine the effect of R. prinoide intercropping on soil nutrient and moisture. The study was conducted in Ganta-afoshum district, eastern zone of Tigray regional state where smallholder farmers practice R. prinoide intercropping. Soil samples were taken from farmland with dense, medium and sparse density of R. prinoide intercropping and from farmland without trees as a control for analysis. The density of the trees significantly affected the soil bulk density (P<0.05). Soil moisture content significantly increased with increasing soil depth and by the interaction effects of soil depth and density (P<0.05). Soil nitrogen concentration significantly influenced by the density and soil depth (P<0.05). Soil phosphorus and potassium concentration significantly affected by soil depth (P<0.05). Lower mean soil pH values were observed for soils under the farm with dense trees as compared to soils in open farm. Overall, the enhancing and exploitative effects of R. prinoide intercropping on soil nutrient and moisture is minimal. This could be the reason for being practiced and maintained by most farmers.

The use of vermi-compost in northern Ethiopia is not a common practice. It is, therefore, important to understand the possible impediments through studying its chemical and biological properties and its extra contribution compared to other composting techniques. Four compost types (vermi-compost, conventional compost, farmers' compost and community nursery compost) with three replications were used in this study. The farmers' and community nursery compost samples were collected from different places in Tigray; whereas, the vermi-and conventional composts were prepared at Mekelle University following a standard composting procedure. Six major composting materials were identified in the visited sites from farmers' and community nursery foremen's interview. These composting materials were also used for the vermi-and conventional composting. Twelve composite compost samples were taken for analysis of macro-and micro-nutrients. The results of the experiment showed that for all treatments, despite of having high content of total C (5.04 -10.67%), the C/N ratio (12.19 -12.22) was low. This suggests that as the C/N ratio is lower than the threshold (< 30), mineralization is faster, nutrients eventually become available and a large amount of N is lost. Soil pH, exchangeable Magnesium (ex.Mg), exchangeable Potassium (ex.P), available Phosphorus (ava.P), and Cation Exchange Capacity (CEC) showed significant differences among the different composting techniques. Among the selected compost types, ex.Mg, ex.Ca and av.P were higher for vermi-compost. The lowest was recorded in community nursery compost. The use of vermi-compost is, therefore, very helpful in terms of providing beneficial soil nutrients as compared to other compost types.