Slash and burn agriculture is no longer feasible due to the rising population pressure and a dwindling resource base. Crop production intensification is required to produce more food per unit area of land, while rebuilding soil fertility. We explored the impact of reallocation of limited resources on crop productivity across farms of different resource endowment in central Mozambique. The results suggested that decreasing the cropped area and concentrating resources (fertiliser, manure and labour within the farmers' means) to smaller fields can increase total farm maize production for poor as well as relatively richer farmers in central Mozambique, but that the fertility of the retained and abandoned land is important for the overall outcome. Concentrating resources to smaller areas would in most cases also lead to increased concentrations of soil organic carbon (SOC), indicating positive effects on soil fertility and crop productivity in the long term. However, this apparently does not apply when only fertiliser is used and if harvest residues and weeds are removed or burnt. Organic inputs are thus also required, such as retention of crop residues, and applications of manure if available can further increase SOC. The study has revealed that sustainable intensification or crop production requires that multiple constraints be addressed simultaneously. Success of crop intensification options will also depend on proper targeting to different farm types as well as variability in soil fertility. Differences in resource ownership and bio-physical circumstances lead to different opportunities for individual farmers even within the same area. While targeted interventions for individual farmers might not be feasible, targeting defined farmer/endowment groups may be a sustainable pathway to increase productivity. Although smallholder farmers in sub-Saharan Africa (SSA) have limited assets, the study revealed opportunities to increase crop productivity without substantial capital inputs, but more efficient use and targeting.