Raising productivity of maize-based cropping systems in eastern and southern Africa: Step-wise intensification options

An ex ante evaluation of step-wise intensification sequences to improve maize yields in rain-fed systems in eastern and southern Africa was undertaken using crop simulation analysis. Baseline yields of farmers' current practice were established through farmer surveys and a participatory modeling approach. Small investments, e.g. low doses of N fertilizer or legume residues and improved weed control, can dramatically increase farmers' yields, i.e. 40-150%, and maintain yield stability across seasons. Higher productivity is possible with higher investments (hybrid seed and high fertilizer N) but at the expense of increasing seasonal variability in both yield and returns on investment. The analysis points to N, not water availability as an overwhelming primary constraint to production for large numbers of poor and average performing farmers. Increasing the use of N fertilizer is therefore the essential first step to intensification of maize production across large areas of eastern and southern Africa. Farmers will gain yield benefits (40%) from improved weed control using herbicides with implied labor-saving benefits. In the near term, with the low soil fertility base, yield increases through improved germplasm are likely to be adequately served by open pollinated varieties. Given low production of stover and competing feed requirements, uptake of N fertilizer will be critical to the feasibility of longer-term adoption of crop residue retention in mixed farming systems. When production increases, co-limitation of other resources (water, P, K) will become important management considerations but, in the meantime, the limiting factor paradigm is highly relevant to informing Africa's agricultural development agenda