the absence of chemical fertilizer,
the yield potential of maize remains
low, around 1 t/ha.

Mechanization increases as one
moves northward and inland. In
the coastal forest zones, mechaniza-
tion is practically nonexistent, and
virtually all farming operations are
performed manually using cut-
lasses and hoes. Some degree of
mechanization has occurred in the
savanna zones, where fields are
less obstructed by trees and thus
more accessible to machinery. In
addition, labor constraints appear
to be more severe in the savanna
because of the much more clearly
defined growing seasons, which
lead to sharp peaks in the demand
for labor (Carr 1989). In the more
heavily forested areas of the south-
ern Guinea savanna, where try-
panosomiasis (sleeping sickness) is
a major problem for cattle, mecha-
nization is still not widespread, but
in many parts of the northern
Guinea savanna, where the effects
of the disease are less severe,
animal traction has become well
established. Plowing as well as
weeding are often done with ox-
drawn implements, and animal
carts are used for transport. Trac-
tor adoption has occurred in a few
areas, often with the help of direct
or indirect subsidies, but the use of
tractors has yet to prove economi-
cally viable throughout much of the
region.

The choice of technology to prepare
land has important implications for
soil fertility, especially on the re-
gion's shallower soils. Unless it is
carefully managed, heavy machin-
ery can lead to serious soil degrada-
tion and can cause dramatic yield
declines after only three to four
years of continuous cultivation. Ox
plowing degrades the soil less than
tractor plowing, but in some areas
the use of oxen is seriously con-
strained by trypanosomiasis, as
well as by the absence of a tradition
of keeping cattle.


Well-developed land markets are
practically nonexistent in western
and central Africa. Credit markets
are generally underdeveloped,
although small loans are often
available from informal savings
associations and thrift societies.
These features are consistent with
the present relative abundance of
land. However, land for agriculture
is becoming increasingly scarce,
and this scarcity may lead to
further development of markets for
land and credit.

The prevalence of well-developed
labor markets is a bit puzzling, be-
cause labor markets tend to be


poorly developed where land is
relatively abundant (Binswanger
and McIntire 1987). The labor
markets of western and central
Africa are fed by two distinct types
of migration: seasonal migration
(which occurs when peak labor
demands in neighboring production
regions do not coincide), and per-
manent migration (which occurs
when the difference in wage rates
between one area and another
exceeds the costs of moving). Both
types of migration are expected to
increase as population pressure
leads to greater intensification of
production in zones of high
potential.


Eastern Africa


Figure 7. Maize germplasm color by region, sub-Saharan Africa, 1983-87.