a sexually-reproduced, allogamous species, behave differently from those in an inbred, vegeta-
tively-propagated crop such as potatoes. The 'purity' of individual cultivars planted in field
mixtures is less in an outbreeder such as maize, while the possibilities for farmers themselves to
improve the crop through rustic forms of recurrent selection are greater.

As in the case of potatoes, many farmers plant both early and late maturing maize cultivars in
order to manage seasonal food gaps, to meet varied end uses of the crop, and to manage
environmental hazards (uncertain rainfall, diseases, pests). Maize farmers in parts of Zambia, for
example, plant traditional short-term cultivars (100-120 days) early in the season to obtain food
and because they taste better as green maize than do the later-maturing hybrids SR52 and ZH1
(170 days), which are produced mainly for sale. Zambian farmers give priority to the planting of
traditional varieties, which delays planting of the hybrids that require a 170-day season; 25% of
the hybrids are planted with only 125 remaining days of rain. When asked whether an improved
120-day cultivar would be useful to them, 96% of the farmers thought it would, and 63%
mentioned the advantage of early food (CIMMYT, 1978).

In Zimbabwe, farmers in Mangwende use maize varieties with differing times to maturity to
manage the variable timing of the rains. An October start to the rainy season results in first
plantings of SR52, a 170-day variety with high yield potential. If farmers have to replant because
of early drought, or delay planting because of late onset of the rains, they switch to shorter-cycle
cultivars such as R201 or R200 (both 135-140 days). Multiple plantings are common, and late
plantings of R201 or R200 extend into January. Late plantings help to insure against losses in the
crop planted earlier and allow a spread of oxen use over a longer period (Shumba, 1985).

The relative economic value of maize stover and grain also affects farmers' choice of cultivar. In
Somalia, there is a market for maize stalks that have been cut and dried. In land-scarce central
Kenya, some farmers prefer to plant a proportion of their land to the 600-series maize hybrids,
rather than the 500-series recommended for the zone, because its larger plant structure provides
more biomass for stall feeding of dairy cattle, a major source of cash for many households.

Farmers in the densely-settled parts of western Kenya show the same interest in maize stover.
Both green plant material and dry maize stover are important sources of cattle feed, and proposals
for two adaptive experimental programmes have been identified (Wangia, 1980). One was to
examine the increase in maize plant density needed to increase fodder production without
sacrificing grain yields in both the long and short rains. The second was to examine the effects
on grain and fodder yields of alternative times of picking the leaves and tops of maize when green.


Breeding Implications of Farmers' Cultivar Diversification

In industrialized economies, field mechanisation and consumer markets favour genotypic and
phenotypic uniformity. Standardised plants and products are less relevant to Africa's resource-
poor farmers. Crop breeding in Africa can benefit from the comparative advantage of the skilled
labour of small farmers in handling cultivar diversity, and in giving detailed attention to
individual plant types. Understanding decisions about the adoption of new cultivars requires
knowledge of farmers' present diversification strategies. This is not to suggest that scientists


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