after being fully dried, are stored, either on the cob or as
shelled grain, and then milled into fl our. The advantage of
maize over millet and sorghum is its relatively high yield and
resistance to pest attacks in the fi eld, as the grains are fi xed
on a cob that is usually covered by a tight sheath. Maize is
widely preferred by African consumers and is replacing millet
and sorghum in many parts, even where the climate is
only marginal for this crop. Commercial maize farming has
led to the development of high-yielding varieties; the fi rst of
these were from Zimbabwe, where several “SR” varieties
were very successful. They have had the disadvantage of
requiring other agricultural inputs, however, and often have
greater susceptibility to pest attacks both pre-harvest, due
to incomplete sheath cover, and post-harvest, due to softer,
more easily eaten grain. There are many local and improved
varieties. Most smallholders grow mixtures of local and improved
varieties in their fi elds, although some do grow highyielding
hybrid maize (especially in southern Africa). Very
often these crops are sold soon after harvest, both to avoid
losses in storage and because farmers are in urgent need of
cash after the harvest.