Impact of farmland exclosure on the productivity and sustainability of a mixed crop-livestock system in the Central Rift Valley of Ethiopia

Livestock provides numerous benefits to smallholders in sub-Saharan Africa, but also represents a potential agent of environmental degradation. Exclosures have been implemented in grazing areas for the past decades in Ethiopia and have been effective in regenerating natural vegetation, controlling soil erosion and increasing soil fertility. More recently, the principles of exclosure have been applied to farmland in pilot areas of Ethiopia. This paper analyzes the impact of eight years of farmland exclosure in the Central Rift Valley of Ethiopia. The performance of 'exclosed farms' (EF) - in which livestock was excluded from the farmland throughout the year - was compared to the performance of neighboring 'open grazing farms' (OF) - in which fields were open for aftermath grazing in winter. EF and OF had significantly different feed and fuel use strategies. Compared to OF, EF relied less on cereal residues, farmland grass, and livestock dung, and more on biomass produced in the communal grazing area (trees and grass) and tree biomass produced on-farm. Because of these different patterns of feed and fuel use, more biomass - in the form of crop residue, manure and compost - was available as soil amendment in EF. This translated into significantly more fertile soils and significantly higher tef yields in EF as compared to OF (1980 +/- 644 kg ha(-1) in EF vs. 1173 +/- 434 kg ha(-1) in OF). These results demonstrate that farmland exclosure is a practical pathway toward sustainable intensification. However, attention should be drawn to three points: (1) the approach impacted positively on crop productivity, but had a negligible impact on livestock productivity, (2) EF livestock still depended partially on grazing (outside of the exclosure) for their acquisition of feed, pointing at the fact that zero-grazing sensu strict may not be realistic in semi-arid areas of Ethiopia, and (3) land rehabilitation through controlled grazing may only be feasible in particular geographic locations (e.g., physical barriers preventing outside livestock to access the area, and presence of alternative grazing areas in the vicinity). (C) 2015 Elsevier B.V. All rights reserved.