Interdisciplinary on-site evaluation of stone bunds to control soil erosion on cropland in Northern Ethiopia
Soil and Tillage Research
Division Soil and Water Management, K.U. Leuven, Celestijnenlaan 200E, B-3001 Heverlee, Belgium; Department of Land Resources Management and Environmental Protection, Mekelle University, P.O. Box 231, Mekelle, Ethiopia; Physical and Regional Geography Research Group, K.U. Leuven, Celestijnenlaan 200E, B-3001 Heverlee, Belgium; Relief Society of Tigray, P.O. Box 20, Mekelle, Ethiopia; Department of Biology, Evolutionary Biology Group, University of Antwerp, Antwerp, Belgium; Faculty of Business and Economics, Mekelle University, P.O. Box 231, Mekelle, Ethiopia; Department of Agriculture and Forestry Economics, Royal Museum for Central Africa, B-3080 Tervuren, Belgium; ADCS Food Security Project, P.O. Box 163, Adigrat, Ethiopia
Since two decades, stone bunds have been installed in large areas of the Tigray Highlands, Northern Ethiopia, to control soil erosion by water. Field studies were conducted to quantify the effectiveness, efficiency, side effects and acceptance of stone bunds. Based on measurements on 202 field parcels, average sediment accumulation rate behind 3-21 year old stone bunds is 58 t ha-1 year-1.The Universal Soil Loss Equation's P-factor for stone bunds was estimated at 0.32. Sediment accumulation rates increase with slope gradient and bund spacing, but decrease with bund age. Truncation of the soil profile at the lower side of the bund does not lead to an important soil fertility decrease, mainly because the dominant soil types in the study area (Regosols, Vertisols and Vertic Cambisols) do not have pronounced vertical fertility gradients. Excessive removal of small rock fragments from the soil surface during stone bund building may lead to a three-fold increase in sheet and rill erosion rates. Negative effects of runoff concentration or crop burial by sediment deposition due to bunds were only found over 60 m along 4 km of studied bunds. As the rodent problem is widespread and generally not specific to stone bunds, it calls for distinct interventions. On plots with stone bunds of different ages (between 3 and 21 years old), there is an average increase in grain yield of 53% in the lower part of the plot, as compared to the central and upper parts. Taking into account the space occupied by the bunds, stone bunds led in 2002 to a mean crop yield increase from 0.58 to 0.65 t ha-1. The cost of stone bund building averages €13.6 ha-1 year-1, which is nearly the same as the value of the induced crop yield increase in 2002 (€13.2 ha-1 year-1). Besides positive off-site effects such as runoff and flood regulation, the enhanced moisture storage in deep soil horizons on both sides of the bunds indicates that the stone bund areas can be made more productive through tree planting. We conclude that from the technical, ecological and economical point of view, the extensive use of stone bunds, involving people's participation, is a positive operation. Overall, 75% of the farmers are in favour of stone bund building on their land, which is a clear indication that the local community perceives this conservation measure as being beneficial. © 2006 Elsevier B.V. All rights reserved.
Agriculture; Erosion; Sediments; Crop yield; Soil and water conservation; Stone bund building; Soils; crop yield; deposition; embankment; farmers attitude; interdisciplinary approach; local participation; perception; soil conservation; soil erosion; soil profile; soil type; Agriculture; Farm Crops; Infestation; Rodents; Soil Erosion; Yield; Africa; East Africa; Ethiopia; Sub-Saharan Africa; Tigray; Rodentia