Stone bunds for soil conservation in the northern Ethiopian highlands: Impacts on soil fertility and crop yield
Soil and Tillage Research
Laboratory for Soil and Water Management, K.U. Leuven, Vital Decosterstraat 102, B-3000 Leuven, Belgium; Physical and Regional Geography Research Group, K.U. Leuven, Redingenstraat 16, B-3000 Leuven, Belgium; Department of Land Resources Management and Environmental Protection, Mekelle University, P.O. Box 231, Mekelle, Ethiopia; Relief Society of Tigray, P.O. Box 20, Mekelle, Ethiopia; Royal Museum for Central Africa, B-3080 Tervuren, Belgium
In the Ethiopian highlands, large-scale stone bund building programs are implemented to curb severe soil erosion. Development of soil fertility gradients is often mentioned as the major drawback of stone bund implementation, as it would result in a dramatic lowering of crop yield. Therefore, the objectives of this study are to assess soil fertility gradients on progressive terraces and their influence on crop yield, in order to evaluate the long-term sustainability of stone bunds in the Ethiopian Highlands. The study was performed near Hagere Selam, Tigray and comprises (i) measurement of Pav, Ntot and Corg along the slope on 20 representative plots and (ii) crop response measurement on 143 plots. Results indicate that levels of Pav, Ntot and Corg in the plough layer are highly variable between plots and mainly determined by small-scale soil and environmental features, plot history and management. After correcting for this "plot effect" a significant relationship (p < 0.01) was found between the position in the plot relative to the stone bund and levels of Pav and Ntot, which are higher near the lower stone bund, especially on limestone parent material. For Corg and on basalt-derived soils in general no significant relationship was found. Although soil fertility gradients are present, they are not problematic and can be compensated by adapted soil management. Only in areas where a Calcaric or Calcic horizon is present at shallow depth, care should be taken. Crop Yields increased by 7% compared to the situation without stone bunds, if a land occupation of 8% by the structures is accounted for. Yield increased from 632 to 683 kg ha-1 for cereals, from 501 to 556 kg ha-1 (11%) for Eragrostis tef and from 335 to 351 kg ha-1 for Cicer arietinum. No negative effects reducing stone-bund sustainability were found in this study. Soil erosion on the other hand, poses a major threat to agricultural productivity. Stone bund implementation therefore is of vital importance in fighting desertification and establishing sustainable agriculture in the Ethiopian highlands. © 2005 Elsevier B.V. All rights reserved.
Erosion; Regional planning; Soils; Sustainable development; Crop response; Slow-forming terraces; Soil fertility gradients; Stone bunds; Soil conservation; crop yield; soil conservation; soil erosion; soil fertility; terracing; upland region; Africa; East Africa; Ethiopia; Sub-Saharan Africa; Cicer arietinum; Eragrostis; Eragrostis tef