Maize is present in many African farming systems. Yield increases have however been modest overall, with greatest improvement in irrigated and commercial farming systems (Spencer, 2004). Introduction of improved maize germplasm has had a significant impact on maize production in Africa. In favoured areas under farm conditions, hybrids have shown yield gains of at least 40 percent over local unimproved material (Smale and Heisey, 1994). In dry areas, hybrids have provided at least a 30 percent yield gain (Rohrbach, 1989; Lopez-Pereira and Morris, 1994). Especially notable is the rapid adoption of improved maize varieties in the savannah areas of Western Africa, particularly Nigeria, and important maize growing regions in Ethiopia, Ghana, Mali, Senegal and Zaire (Maredia et al., 1998). Breeding programs involving the International Institute for Tropical Agriculture (IITA) and The International Maize and Wheat Improvement Center (CIMMYT) have produced open-pollinated varieties, which in tropical areas have an estimated yield gain of 14-25 percent over local materials (Morris et al., 1992).

Apart from improved varieties, agronomic measures to improve soil fertility have led to dramatic yields improvements. Application of manure in Zimbabwe, for instance, raised yield to more than 6 tonnes per hectare (Mapfumo and Giller, 2001). In West Africa, the Sasakawa Global 2000 initiative has introduced a package of improved maize technologies to increase productivity. Farmers were given management training plots of 0.25 hectare each and supplied with credit to purchase inputs (i.e., seeds of improved crop varieties, fertilizers and pesticides). The results are presented in Table 4.2. While yield increases are substantial, the variation in yield was also high (Brader, 2002).

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