Nitrogen (N) deficiency, and associated poor sod fertility, are common features of smallholder fields cropped to maize in southern Africa. Use of maize genotypes with improved N-use efficiency (NUE) implies an important yield benefit at modest additional recurrent cost to the farmer, making them relatively attractive for adoption by resource-poor African smallholder farmers. However, current estimates of genetic gain for NUE in maize would limit grain yield improvements to around 25 to 40% (O.3 to 0.5 t ha-1) of current smallholder farm yields. This is far short of the doubling or tripling of average maize grain yields required to feed southern Africa into the initial decades of the 21st century. In well-watered maize areas, larger amounts and improved types of inorganic and organic N fertilizer inputs and their better management are likely to continue to provide most productivity gains. This paper presents a strategy of modest inorganic fertilizer inputs combined with biological N fixation and organic matter from additional legumes. Several promising technological interventions-better targeted inorganics involving micronutrient supplementation, practical legume systems, combined high quality organic matter with inorganics, and interaction with moisture and with other management interventions-are discussed and their technological and economic feasibility is assessed. We also consider research costs and time lags, probability distributions of research outcomes, necessary institutional and policy support for widespread adoption, management complexity, and effective ways of deploying soil fertility technologies on smallholder farms through the integration of research and extension and the institutions involved .

English

9801|AGRIS 9702|anterior|R97-98PROCE|FINAL9798

Jose Juan Caballero

CIMMYT Publications Collection