Maize Types Grown in Africa African farmers plant many differ- ent types of maize. White maize predominates throughout the continent, except for the Sahel, where the mix is slightly more balanced between white and yellow materials (Figure 7). Within each color type, the variability in other physical grain characteristics is extensive. In Africa as elsewhere, use of improved maize germplasm is difficult to estimate precisely, because improved and unimproved materials cannot always be distin- guished easily. Since maize is an open-pollinated crop, maize plants in one field often cross with plants in nearby fields if both crops flower at the same time. When improved varieties are introduced in an area where unimproved varieties are grown, mixtures often result, until farmers-and breeders-cannot always tell which varieties are improved and which are not. Alternative methods of determining pedigrees, such as tracing the sources of seed, may provide more valid estimates than simple visual inspection. A further complication in assessing the adoption of im- proved varieties is that the defini- tion of "improved" material varies. Improved materials are sometimes defined as certified seed purchased during the previous two to three years; in other cases, seed contain- ing mostly improved germplasm is classified as improved. Statistics on adoption of improved materials should be interpreted with these qualifications in mind. Most African smallholders continue to plant unimproved traditional varieties, while most large-scale commercial farmers grow improved 4 Smallholders in a few countries, including Kenya, Nigeria, Senegal, Zambia, and Zimbabwe, do plant improved maize. maize.4 Little empirical research has been done in Africa on eco- nomic factors underlying farmers' decisions for and against adopting improved maize varieties. Differ- ences in the rate and degree of adoption can be explained partly in terms of demand (for example, farmers sometimes cannot afford improved seed), but inadequate supplies of improved germplasm usually play a much larger role in slowing the rate and degree of adoption. Of particular importance is the availability of appropriate materials, which depends on local crop improvement programs and/or local seed production capacity. Maize breeding in eastern and southern Africa for a long time focused primarily on the needs of commercial farmers, who them- selves contributed to the germ- plasm improvement process by selecting materials in their own fields. Today, most national agricul- Cumulative % of farmers adopting 1964 1966 1968 tural research programs in the region produce improved germplasm with varietal character- istics desired by both large- and small-scale farmers. The fact that both groups are often interested in the same characteristics is illus- trated by the experience of Kenya, where the area under improved hybrid maize increased from 120 ha in 1963 to over 1,000,000 ha in 1988. In high potential zones, small-scale producers as well as es- tate farmers demonstrated great enthusiasm for the commercial hybrids developed by the national program; smallholders' adoption lagged only in less favorable pro- duction environments where hy- brids did not perform so well (Figure 8). Hybrids have enjoyed similar success in Zimbabwe and parts of Zambia, demonstrating what can happen when improved germplasm is made available to small-scale farmers (see "Hybrid Maize in Sub-Saharan Africa: Problems and Prospects," p. 21). 1970 1972 1974 Source: Gerhart (1975). Figure 8. Adoption of hybrid maize in four zones in Kenya.