Published online by Cambridge University Press: 27 February 2018
In sub-Saharan Africa mixed crop-livestock systems predominate in the semi-arid, sub-humid and cool highland zones. In these areas, systems intensify and crops and livestock become increasingly integrated as the human population increases and land becomes a more important constraint than labour (Boserup, 1965; McIntire et al., 1992). As intensification progresses, use of crop residues moves from open access to crop fields, following harvest, to labour intensive management of cereals as dual-purpose crops.