Water balance components of the potential agricultural grabens along the Rift Valley in northern Ethiopia

Region: Ethiopia's Rift Valley. Focus: matching agricultural water demand and supply is a growing policy challenge in drylands. We investigated the water balance components in Raya (3507 km(2)) and Ashenge (80.5 km(2)) grabens. The rainfall depth, river discharge, abstraction, climate and soil data (2015-2017) were used to address the research question. New hydrological insights: the average annual rainfall of the graben's escarpment and its bottom was 806 +/- 162 and 508 +/- 110 mm, respectively. Heavy rains produce floods up to 732 m(3) s(-1) in the rivers that flow into the Raya graben. Moreover, greater runoff and river discharges volumes were recorded at the graben escarpments than at the graben bottom outlets (p < 0.001) due to the greater contributing area (p < 0.001, R-2 = 0.98) and headwater elevation (p < 0.001, R-2 = 0.98). About 24% of the water entering both graben bottoms comes from the runoff from the adjacent slopes, and about 40% of the runoff reaching the Raya graben bottom flowed out at the outlet. About 76% and 77.5% of the annual rainfall was lost through evapotranspiration from the Raya and Ashenge grabens, respectively. So about 16% and 33% of the average annual inflows infiltrated into the sediments in the Raya and Ashenge grabens, respectively. These insights provided by this study into the water balance in grabens along the Rift Valley can be used to help achieve sustainable agricultural development

Arbuscular mycorrhiza effects on Faidherbia albida (Del.) A. Chev. growth under varying soil water and phosphorus levels in Northern Ethiopia

Tree seedling establishment, survival and growth in dryland areas is greatly impacted by water, land use effects and soil nutrient availability. Arbuscular mycorrhizal fungi (AMF) can have a substantial effect on water and nutrient uptake by seedlings and are affected by nutrient application, water availability and inoculum source. In this study, we examined the effect of AMF inoculation, phosphorus application levels, soil water status, and inoculum source on the growth of Faidherbia albida seedlings. Two greenhouse experiments were conducted on F. albida seedlings: to compare (a) ±AMF inoculation, at three levels of volumetric soil water content (field capacity (FC), 60% of FC and 20% of FC), and three AMF inoculum sources (derived from cultivated land, grazing land and area exclosure); (b) ±AMF inoculation, at four levels of phosphorus application (0, 25, 50 and 100 mg kg−1) and three AMF inoculum sources. Inoculation with AMF, higher soil water and higher P application significantly increased the growth of seedlings (P < 0.05). F. albida seedlings responded positively to increased water levels. The highest growth and AMF colonization of seedlings was recorded under the lowest water stress with AMF inoculum from area exclosure followed by grazing land inoculum source. The lowest growth was recorded under the highest water stress and cultivated land inoculum source. Plant growth and biomass were positively correlated with increased soil P application, however, AMF colonization decreased with increasing P application. Applying P and inoculating F. albida seedlings with indigenous AMF under low water stress enables optimum plant growth improvement in dryland farming systems

An assessment of integrated watershed management in Ethiopia

Sustainable participatory watershed management is an approach promoted by the Ethiopian government to restore natural resources and agricultural productivity across the country. This comparative study between six watershed programs shows that this approach increases farmers’ food security and incomes (around 50% on average), as well as their resilience to drought and other climate shocks. However, the study also confirms that the nature and scale of impact can vary significantly between watershed programs. The success of watershed management depends on multiple factors from the hydrological profile of the watershed to the local social and economic environment. Tailoring watershed interventions to the local context, associating conservation and livelihoods activities, and providing further financial and technical support to watershed committees are among the recommendations of this paper

The Effects of Land Use and Landscape Position on Soil Physicochemical Properties in a Semiarid Watershed, Northern Ethiopia

Understanding topography effects and assessing the soil properties in different land use is an essential first step for sustainable soil management. Hence, land use type and altitudinal gradient on selected soil parameters were studied in Ayiba watershed, northern Ethiopia. Thirty composite soil samples were collected from 0 to 30 cm of soil depth under four land use types across three altitudinal gradients and were analyzed for selected soil parameters following the standard procedures. A significant main effect of land use and altitudinal gradient on the content of the soil particles was noted. Results also indicated that the bulk density (BD), total porosity (TP), and Pav of the soil are significantly different (p < 0.05) in the watershed because of land use type and altitudinal gradient. Barren land and higher altitude landscapes have the highest BD, and the lowest TP, and grassland and lower altitude landscapes have the lowest BD and high TP. Intensive cultivation accompanied by natural land conversion and erosion due to the rugged landscape nature caused high BD and low TP. Analysis of variance results also shows the significant interaction effect of land use type and altitudinal gradient on EC, SOM, SOC (p < 0.001), and pH-water (1:2.5), and TN (p < 0.01). The Pearson correlation of SOM with TP, TN, MC, and clay content showed a strong positive relationship. But, SOC, TN, and clay content were negatively correlated with BD. Soils of the study watershed are found in low to optimum rating levels in their selected physicochemical properties. Overall, the results show that land use and topography gradient significantly affected soil physicochemical properties in the study watershed. Therefore, soil management options should focus on scenarios that could improve the soil conditions to enhance crop production on a sustainable basis

Runoff and sediment-associated nutrient losses under different land uses in Tigray, Northern Ethiopia

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Land suitability analysis for sorghum crop production in northern semi-arid Ethiopia: Application of GIS-based fuzzy AHP approach

The mismatch between the actual requirements and what is actually implemented in a given land could be avoided through land suitability evaluation through its contribution in identifying the inherent land potentials and constraints. This study aims to assess suitability for sorghum (Sorghum bicolor L. Moench) crop by integrating geographic information system (GIS), fuzzy set models and analytical hierarchy process (AHP) methods. Soil, climate and topographic characteristics were considered in the study. As evidenced from the model output, 29,534 ha (30.54%), 34,984.74 ha (36.17%), 17,455 ha (18.05%), 14,744.61 ha (15.24%) of the area is moderately suitable, marginally suitable, currently not suitable and permanently not suitable for sorghum crop production respectively. Slope gradient, altitude, temperature, length of growing period, available water capacity, mean weight diameter, total nitrogen, available phosphorus and soil organic carbon contents were found the main limiting factors constraining cultivation of that crop in the area. Organic and inorganic fertilizer application, tillage and soil and water management activities are needed to boost the productivity of the area