Soil Science

Soil Geomorphology in the High Elevation: Soil Formation, Landform Relations and Indigenous Knowledge of Guna Mountain, Ethiopia

2026-09-04T06:14:00Z

Soil Geomorphology in the High Elevation: Soil Formation, Landform Relations and Indigenous Knowledge of Guna Mountain, Ethiopia Getahun, Mekonnen The distribution of soil in high mountain environments is shaped by various soil forming factors. Soil geomorphologists analyze key pedological characteristics to estimate the age of Quaternary deposits, assess landscape stability, and infer past climate changes. Understanding the influence of these soil-forming factors allows one to reveal important aspects of soil distributions as affected by landscape evolution that might otherwise remain hidden. This study seeks to explore and clarify the complex interactions between geomorphic landscapes and soil properties in Mount Guna, Northwest Ethiopia. Shuttle Radar Topographic Mission (SRTM) and 30-m resolution DEM data were analyzed using QGIS to characterize the area’s geomorphology. Soil samples were collected from representative landform units with a total of 85 soil profiles described and sampled across seven topographic transects, covering various elevation belts, lithologies and land cover types. Standard physicochemical analyses were performed on all pedons. The soil map was developed by integrating local geological mapping, geomorphological mapping and the soil survey observations, with landforms serving as the primary basis for delineating soil mapping units. Six landform units were identified: ridge-top, platform, steep upper slopes, concave slope, and valley bottom. The Reference soil groups (RSG) identified in the study area includee Andosols, Phaeozems, Leptosols, Cambisols, Regosols, Luvisols and Vertisols. Silandic/Vitric Andosols are present on the mountain’s summittal ridge, while very shallow to shallow Leptosols dominate the ridge top. Moderately deep to deep soils, such as Luvisols and Phaeozems, are found on the middle slopes. In the valley bottom, the soils are deep, moderately well-drained, and clayey in texture, comprising Vertisols, Cambisols and Luvisols. The majority of the identified reference soil groups are well aligned with the previous studies in the Afro Alpine environment of the East African Rift Valley systems. The findings suggest that landform-soil processes are largely controlled by the area’s physiographic position, drainage, and slope and erosion dynamics. Studying the connection between soils and geomorphology on Mount Guna can improve methods for updating global soil datasets like the Harmonised Soil Map of Africa or SoilGrids. This dissertation also highlights the importance of farmers' indigenous knowledge in enhancing our understanding of local soils and their management. The research examined the similarities and differences between scientific and traditional soil knowledge in Mount Guna and nearby communities in Ethiopia's highlands. The findings revealed that farmers have a deep understanding of their soils, which aligns closely with scientific research and can be utilized in extension activities to improve soil management practices. Regionally, a better understanding of the soils and geomorphology in the Tana Basin is critical for improving surface hydrology management, as Mount Guna serves as a key water source for the basin. Additionally, given the area's rapid agricultural growth and livestock grazing, gaining further insights into soil characteristics is essential for promoting sustainable land management practices.

Utilization of Water Hyacinth-Derived Biochar and Compost for Soil Amendment and Crop Production in Northwestern Ethiopia

2026-09-04T06:09:43Z

Utilization of Water Hyacinth-Derived Biochar and Compost for Soil Amendment and Crop Production in Northwestern Ethiopia Gezahegn, Ashenafei Since 2011, water hyacinth (WH; Eichhornia crassipes) has become a significant threat to Lake Tana, Ethiopia. Managing WH is challenging due to rapid growth and difficulties in disposing of harvested biomass. However, utilizing WH biomass for agricultural use can aid weed control, improve soil fertility, and enhance crop production. The ways to use the harvested WH biomass include converting into biochar and compost. These can be combined with inorganic fertilizers and applied to the soil for enhanced benefits. The research objectives were to: (1) investigate the impact of pyrolysis temperature on the physicochemical properties of WH biochar (WHB), (2) assess the effects of WHB produced at different temperatures on maize (Zea mays L.) growth and soil properties, (3) evaluate the combined effects of WHB and inorganic fertilizers on soil properties, maize yield, and nitrogen (N) use efficiency, and (4) examine the impacts of combining WHbased compost (WHC) with mineral fertilizers on soil properties and teff (Eragrostis tef (Zucc.) Trotter) yield. The research included four experiments. The first experiment involved converting WH biomass into biochar at three pyrolysis temperatures (350°C, 550°C, and 750°C) and analyzing the physicochemical properties to determine their potential as a soil amendment. The second experiment was a pot trial applied via WHB developed at different pyrolysis temperatures at rates of 5 and 20 t ha -1 , alongside a control (without biochar), to evaluate the effects on maize growth and soil properties. The third experiment examined the field application of WHB (0, 5, 10, and 20 t ha -1 ) in combination with half and full rates of the recommended chemical fertilizers (180/138 kg N/P 2 ), plus a control (without biochar/fertilizer), to study the impacts on acid soil properties, maize yield, and N use efficiency. The fourth experiment assessed the combined effects of WHC (0, 8, 16, and 24 t ha -1 ) and 0%, 50%, and 100% of the recommended mineral fertilizers (80/46 kg N/P 2 O 5 ha -1 ) on soil properties and teff yield. The results show that pyrolysis temperature significantly affected the WHB characteristics, with yield decreasing from 51.0% to 33.3% as temperature increases. Increasing temperature raised WHB pH (9.24 – 11.2), electrical conductivity (28.0 – 44.7 dS m -1 ), C/N ratio, ash, and available nutrients (P, Ca, Mg, and K) while decreasing carbon (C), hydrogen (H), N, and cation exchange capacity (CEC). Additionally, rising temperature increased the surface area, pore volume, and water-holding capacity of WHB. However, the functional groups declined as O 5 ha -1 temperature increased. The pot experiment results revealed that WHB applied at 20 t ha increased maize biomass (shoots by 47.7% and roots by 78.4%). Applying WHBs produced at 350°C and 550°C significantly enhanced soil total N (TN) and CEC compared to the control. However, higher available P (P av ) was recorded from applying WHB produced at 750°C. Chapter 5 presents the effects of combining WHB with mineral fertilizers on acid soil properties, maize yield, and N use efficiency. Applying WHB at the rate of 20 t ha significantly reduced bulk density, and increased porosity and pH, while lowering exchangeable acidity (EA) and Al³⁺ levels. Additionally, WHB boosts P av , organic C (OC), TN, CEC, and exchangeable potassium (Exch. K xii + ). The combination of WHB and chemical fertilizers increased maize grain yield by 33.6% and 30.8% at the half and full fertilizer rates, respectively, with a 10% yield increase (5 and 10 t ha -1 WHB plus full fertilizer) in the second year compared to the first. Nitrogen use efficiency significantly increased, particularly when WHB was applied with half fertilizer rates. Chapter 6 presents findings from the integrated use of WHC and mineral fertilizers. Before field experiments, bioassays confirmed that the WHC had no phytotoxic effects (seed germination index > 80%). Applying WHC increased soil pH by 0.69 units, reduced bulk density (10.3%), and increased soil OC (24.3%), TN (28.6%), P av (80.2%), CEC (26.2%), and Exch. K (112.7%). The EA and Al³⁺ decreased by 72.5% and 78.6%, respectively. The maximum teff grain yield (1.83 t ha -1 ) and total biomass (8.02 t ha -1 ) were achieved with 24 t ha of WHC and full mineral fertilizer integration. Applying 16 or 24 t ha -1 of WHC with half the recommended fertilizer outperformed the sole full fertilizer rate. The study concludes that pyrolysis temperature significantly affects WHB properties as a soil amendment, influencing soil characteristics and plant growth. Controlling the temperature during biochar production is crucial. Combining WHB with chemical fertilizers enhances soil fertility and maize production in acidic soils. Composting WH and integrating it with inorganic fertilizers improves soil characteristics and crop performance. Using WH biomass for soil amendment offers an effective method for weed control and promotes soil fertility and crop productivity. Future studies should explore the long-term effects of integrating WH-derived biochar and compost with inorganic fertilizers across different soil types to validate these findings. -1 -1 -1 +

Effect of Land Use and Land Management Practices on Soil Respiration Dynamics in Upper Blue Nile Basin, Ethiopia

2026-09-04T06:06:26Z

Effect of Land Use and Land Management Practices on Soil Respiration Dynamics in Upper Blue Nile Basin, Ethiopia Fekadu, Genetu Understanding how land use affects soil respiration (Rs) rates will assist us to comprehend global CO fluxes and develop land management plans. This study examines: (1) the impact of land use on Rs in highland and midland agroecology; (2) the effects of land use on heterotrophic (Rh) and autotrophic (Ra) soil respiration in the three contrasting agroecologies Guder (2500–4232 m), Aba Gerima (1500–2500 m) and Dibatie (500–1500 m); (3) the effects of land management practices on seasonal and diurnal Rs dynamics in highland; (4) and the effects of soil amendments on Rs in midland agroecosystems. Data for Rs, soil moisture (S 2 ), and temperature (S ) were recorded monthly. One-way repeated measures ANOVA, Friedman’s nonparametric test, paired t-test, regression, and correlation analysis were used throughout the study. Based on the results, Rs rates were significantly (p = 0.004) higher in khat plantations and teff cropland than in midland grazing land. On the other hand, in the highlands, grazing land showed significantly higher Rs rates than Acacia decurrens and teff cropland (p = 0.002). The Ra values of teff cropland in Guder and Aba Gerima were higher than those of other land uses and lower than those of grazing land in Dibatie. Similarly, the Rh of midland teff cropland was higher than that of other land uses. In the highlands, the Rh values of Acacia plantations were higher than those of other land uses. The results indicated that teff cultivation in relatively humid regions, Guder (1.36 CO T xix 2 μmol m ) and Aba Gerima (2.08 CO 2 μmol m –2 s –1 ) results in higher CO fluxes into the atmosphere than Dibatie (0.80 CO 2 μmol m –2 s –1 2 ). Seasonal Rs rates were significantly different in different seasons (autumn, p = 0.008; winter, p = 0.011; spring, p = 0.011; and summer, p = 0.038) between soil bund and control plots in all seasons. The rate of daytime Rs was significantly higher (p = 0.0002) at 11 a.m. than at other times and lowest at 5 a.m. The Rs levels of B (4.23 ± 0.61 CO 2 μmol m –2 s –1 ) and PAM+L (4.14 ± 0.57 μmol m –2 s –1 ) were significantly higher than those of PAM+B (3.43 ± 0.55 μmol m –2 s –1 ) (p = 0.0003). Overall, different soil and soilrelated factors, such as S m and S , contributed to the variations in the Rs at the study sites. However, in-depth research is needed to evaluate whether land use and management practices significantly contribute CO 2 T to the atmosphere or not.

Soil Bunds, Cover Crops, and Acacia Decurrens Plantation Practices Influence Soil Erosion, Soil Moisture, and Crop Yield in the Abbay Basin, Ethiopia

2026-09-04T06:02:29Z

Soil Bunds, Cover Crops, and Acacia Decurrens Plantation Practices Influence Soil Erosion, Soil Moisture, and Crop Yield in the Abbay Basin, Ethiopia Demissie, Simeneh Land degradation due to accelerated soil erosion is a major socio-economic development and environmental sustainability threat in the highlands of Ethiopia. To reverse these problems several types of sustainable land management (SLM) practices have been implemented in the past 50 years. The interventions were critical to reduce runoff and soil loss and improve soil moisture and land productivity. The study focuses on evaluating the impact of biophysical land management practices on soil erosion and soil moisture in the Guder and Aba Gerima watersheds. Runoff plots were established in the three selected SLM technologies (5 plots on soil bund spacing [27.2, 12.7, 7.87, and 5.45 m], 12 plots on 3 cover crops [bitter lupin, vetch, and sweet lupin], and 3 plots on Acacia decurrens [AD] plantation). From each plot daily runoff and soil loss data were measured. Composite soil samples were collected from the cover crop (CC) and AD plots for pH, organic carbon (OC), total nitrogen, and available phosphorus analysis. For soil moisture analysis 1080 and 366 disturbed soil samples were collected at depths of 0 to 0.5 m and 0 to 0.6 m (at 0.1 m intervals of soil profile) from CCs and soil bund (SB) plots, respectively. The results revealed that SBs and CCs substantially reduced surface runoff. Soil bunds were more effective in reducing runoff than CCs and AD. Year 3 and 4 AD plantations were the least in reducing runoff loss even lower than the control plots. Slope length between consecutive SBs also affects the efficiency of SBs in reducing runoff loss (the narrowest the most efficient). The narrowest SBs, bitter lupin CC, and year 1 AD (better understory vegetation) show the best performance in reducing soil loss. Wider SB spacing, low biomass-producing CCs, and older AD (low understory vegetation and water infiltration) have less efficiency in reducing soil loss but were better than the control. The average seasonal soil water significantly (P < 0.05) decreased with increased SB spacing. In this study, CCs had no substantial effect on soil water content. Cover crop treatments significantly improved OC, total nitrogen, available phosphorus, and dry organic biomass addition. Similarly, OC, total nitrogen, and available phosphorus were improved in AD plots compared to the control. The soil fertility improvement due to SLM practices affects crop yields positively. Adopting optimum SB spacing and fast-growing leguminous CCs (bitter lupin) provides the best economic and environmental benefits. However, further studies will be required to prove the integration impacts of physical with biological SLM practices in different biophysical settings.