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Removal of rock fragments and its effect on soil loss and crop yield, Tigray, Ethiopia (2001)

Nyssen, J. ; Haile, Mitiku ; Poesen, J. ; [et al.]

Wiley

In: Soil Use and Management. 2001; 17(3): 179-187. Published 2001 Sep 01. doi: 10.1079/sum200173.

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Publication Date: 2001-09-01

Print ISSN: 0266-0032

Electronic ISSN: 1475-2743

Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Published by Wiley on behalf of British Society of Soil Science.

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Removal of rock fragments and its effect on soil loss and crop yield, Tigray, Ethiopia (2001)

Nyssen, J. ; Haile, Mitiku ; Poesen, J. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Soil use and management 17 (2001), S. 0

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ISSN: 1475-2743

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract. When the farmers of the Highlands of Tigray (northern Ethiopia) consider rock fragment cover in their fields to be excessive, they remove some of them. In addition, large amounts of rock fragments of all sizes are removed from fields for building stone bunds. Semi-structured interviews indicate that the farmers are often reluctant to take away the smaller rock fragments (i.e. 〈 5 cm across) from their fields, since they believe these benefit soil moisture conservation and protect topsoil from erosion. A field experiment was carried out on a Vertic Cambisol (average slope: 0.125 m m–1), 2 km east of Hagere Selam (subhumid climate). Rock fragments were totally, partially or not removed from the 12 runoff plots (5 m × 6 m) before the beginning of the 1999 cropping season, during which a local mixture of wheat varieties (Triticum spp.) was sown. After harvest, erosion rates were assessed by measuring deposited sediment volume in trenches at the lower side of each subplot, and grain and straw yields were assessed. We found a significant negative relationship between rock fragment cover and soil loss by water erosion. However, the resulting positive relationship between rock fragment cover and grain and straw yield was weak. This might be explained by the fact that the plot did not suffer from drought due to soil and climatic conditions. Detailed analysis showed that cover by medium and large rock fragments (〉 2 cm diameter) showed an optimum percentage cover above which crop yields decrease. A recommendation resulting from this study is to rely on the farmers’ experience: smaller rock fragments should never be removed from the surface of fields during soil and water conservation works; instead rock fragment rich soil can be used to top the stone bunds.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1475-2743.2001.tb00025.x

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Effectiveness of stone bunds in controlling soil erosion on cropland in the Tigray Highlands, northern Ethiopia (2005)

Gebrernichael, Desta ; Nyssen, J. ; Poesen, J. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Soil use and management 21 (2005), S. 0

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ISSN: 1475-2743

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Use of stone bunds to enhance soil and water conservation was first introduced to Tigray, northern Ethiopia in 1981. This study was designed to examine the factors that control the effectiveness of bunds installed on cropland. Qualitative and quantitative assessments of soil loss and sediment accumulation were conducted on 202 plots at 12 representative sites in Dogu'a Tembien district. Mean annual soil loss from the foot of the bunds due to tillage erosion was estimated at 39kgm−1yr−1 or 20tha−1yr−1, a rate which decreased with increasing age of bund. The assessed mean annual soil loss rate by sheet and rill erosion in the absence of stone bunds is 57tha−1yr−1. The mean measured annual rate of sediment accumulation behind the stone bunds is 119kgm−1yr−1/sp or 59tha−1yr−1. The measurements show that the introduction of stone bunds to the region has led to a 68% reduction in annual soil loss due to water erosion. This reduction is due to the accumulation of sediment behind the stone bunds, which occurs faster in the early years after construction and decreases as the depression behind the bunds becomes filled with sediment. New stone bunds are particularly effective in trapping sediment in transport, but regular maintenance and increase in height of the bunds is necessary to maintain their effectiveness. The average USLE P factor for stone bunds in the study area is estimated to be 0.32.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1475-2743.2005.tb00401.x

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The effectiveness of loose rock check dams for gully control in Tigray, northern Ethiopia (2004)

Nyssen, J. ; Veyret-Picot, M. ; Poesen, J. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Soil use and management 20 (2004), S. 0

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ISSN: 1475-2743

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract. Over the last two decades, large gully control programmes have been established in Ethiopia. Based on detailed observations and measurements of 400 check dams in the highlands near Hagere Selam (Tigray, northern Ethiopian Highlands), the effectiveness of the check dam technique was assessed. In this study, catchment area, slope gradient, technical characteristics and the presence of smectite clays are the main factors controlling dam stability. Simple and logistic regression techniques were used to analyse the data. The frequent collapse of dams (39% after two years) is strongly associated with drainage area (A) and slope gradient of the soil surface near the gully (S), the product of these factors (S×A) being a proxy for runoff energy. Good functioning dams have a spillway, apron, concave plan form (when looking downslope) and are built at vertical intervals and with heights that result in a negative slope gradient of the line connecting the spillway and the foot of the upstream dam. Therefore, a reverse slope of this line is recommended. Furthermore, if large cracks are present in smectite-rich soils, the construction of check dams can lead to piping and concentrated flow bypassing the dam. Given that the collapse of some check dams seems inevitable where catchment areas are large or there are steep slopes, it is necessary to repair dams as soon as partial collapse starts and to complement this gully control technique with biological control measures.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1475-2743.2004.tb00337.x

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Social efficiency of bubbles in the Grossman and Helpman endogenous growth model

Nyssen, J.

Amsterdam : Elsevier

Economics Letters 45 (1994), S. 197-202

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ISSN: 0165-1765

Keywords: [JEL classification codes] D62 ; [JEL classification codes] D92 ; [JEL classification codes] O30

Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Topics: Economics

Type of Medium: Electronic Resource

URL: http://linkinghub.elsevier.com/retrieve/pii/0165-1765(94)90134-1

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Soil erosion and conservation in Ethiopia: A review (2015)

Haregeweyn, N., Tsunekawa, A., Nyssen, J., Poesen, J., Tsubo, M., Tsegaye Meshesha, D., Schütt, B., Adgo, E., Tegegne, F.

Sage

In: Progress in Physical Geography

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Publication Date: 2015-11-21

Description: This paper reviews Ethiopia’s experience and research progress in past soil and water conservation (SWC) efforts and suggests possible solutions for improvement. Although indigenous SWC techniques date back to 400 BC, institutionalized SWC activity in Ethiopia became significant only after the 1970s. At least six national SWC-related programs have been initiated since the 1970s and their focus over time has shifted from food relief to land conservation and then to livelihoods. The overall current soil erosion rates are highly variable and large by international standards, and sheet, rill, and gully erosion are the dominant processes. The influence of human activities on the landscape has traditionally been deleterious, but this trend seems to have recently reversed in some parts of the country following the engagement of the communities in land management. The efficiency of SWC measures show mixed results that are influenced by the type of measures and the agro-ecology under which they were implemented; in general, the relative performance of the interventions is better in the drylands as compared with humid areas. Methodological limitations also occur when addressing the economic aspects related to benefits of ecosystem services and other externalities. Although farmers have shown an increased understanding of the soil erosion problem, SWC efforts face a host of barriers related to limited access to capital, limited benefits, land tenure insecurity, limited technology choices and technical support, and poor community participation. In general SWC research in Ethiopia is fragmented and not comprehensive, mainly because of a lack of participatory research, field observations, and adoptable methods to evaluate impacts. A potentially feasible approach to expand and sustain SWC programs is to attract benefits from global carbon markets. Moreover, a dedicated institution responsible for overseeing the research–extension linkage of SWC interventions of the country should be established.

Print ISSN: 0309-1333

Electronic ISSN: 1477-0296

Topics: Geography

Published by Sage

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Spatio-temporal sedimentation patterns in beaver ponds along the Chevral River, Ardennes, Belgium (2013)

M. De Visscher, J. Nyssen, J. Pontzeele, P. Billi, A. Frankl

Wiley

In: Hydrological Processes

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Publication Date: 2013-01-05

Description: With the recovery of the European beaver ( Castor fiber ) and their capacity to engineer fluvial landscapes, questions arise as to how they influence sediment transport, including the spatio-temporal trends and patterns of sedimentation in beaver ponds. The Chevral river (Ardennes, Belgium) contains two beaver dam sequences which appeared in 2004. Volumes of sediment deposited behind the dams were measured and grain size distribution patterns were determined. Flow discharges and sediment fluxes were measured at the in- and outflow of each dam sequence. Between 2004 and 2011, 1710.1 m 3 of sediment were deposited behind the beaver dams, with an average sediment thickness of 25.1 cm. The thickness of the sediment layer was significantly (p 〈 0.001) related to the area of the beaver ponds. Along the stream, beaver pond sediment thickness displayed a sinusoidal deposition pattern, in which ponds with thick sediment layers were preceded by a series of ponds with thinner sediment layers. A downstream textural coarsening in the dam sequences was also observed, probably due to dam failures subsequent to surges. Differences in sediment flux between the in- and outflow at the beaver pond sequence were related to the river hydrograph, with deposition taking place during the rising limbs and slight erosion during the falling limbs. The seven-year-old sequences have filtered 190.19 tons of sediment out of the Chevral river, which is of the same order of magnitude as the 374.4 tons measured in pond deposits, with the difference between the values corresponding to beaver excavations (60.24 tons), inflow from small tributaries, and runoff from the valley flanks. Hydrogeomorphic effects of C. fiber and C. canadensis activity are similar in magnitude. The detailed analysis of sedimentation in beaver pond sequences confirms the potential of beavers to contribute to river and wetland restoration and catchment management. Copyright © 2013 John Wiley & Sons, Ltd.

Print ISSN: 0885-6087

Electronic ISSN: 1099-1085

Topics: Architecture, Civil Engineering, Surveying , Geography

Published by Wiley

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