In addition, competition between
crops commonly occurs when the
demand for labor is at its peak
(Figure 18). This competition can
have severe consequences for food
crops. Faced with allocating scarce
labor either to food crops or to high-
value cash crops such as ground-
nuts and cotton, farmers often
make the economically rational
decision in favoring the cash crops.
Many operations for food crops
must be postponed or omitted
entirely, reducing yields.

Large-scale maize producers can
reduce the peak demand for labor
by investing in machinery (e.g.,
tractors to enable earlier and faster
planting, and cultivation equip-
ment for weeding). However, the
high cost of tractors and their
limited utility on unimproved plots
generally make them an unattrac-
tive investment for small-scale
farmers, unless machinery rental
services are available. Where graz-
ing capacity is sufficient to support
cattle or donkeys (and where
trypanosomiasis is not present),
animals can substitute for human
labor, but many operations must
still be performed manually.

Faced with labor constraints, many
African maize producers adopt
strategies to spread out the demand
for labor-for example, intercrop-
ping, planting sequentially, and
distributing crops between plots
with different soils and moisture re-
gimes. Diversification strategies
typically reduce maize yields but
frequently increase total agricul-
tural output per unit land area and
raise overall returns to labor. Also,
such strategies tend to reduce the
risk of losses if a single component
in the cropping system fails.


When evaluating potential produc-
tion technologies for maize, re-
searchers have not always consid-
ered the relationship between the
opportunity cost of labor and labor
productivity. Productivity increases
are generally reported in terms of
yield gain per unit land area,
rather than in terms of yield gain
per unit of labor. However, the
latter measure may be more rele-
vant if labor is the limiting factor.
New technologies that increase the
productivity of land may also in-
crease the productivity of labor and
other scarce resources. But if the
opportunity cost of agricultural
labor is high (for example, because
of attractive off-farm employment
opportunities), returns to labor
invested in yield-increasing tech-
nologies for maize may be small or


nonexistent (Table 7). Farmers may
then decide not to adopt the new
technologies, to adopt them only
partially, or to adopt them while
modifying other practices to
accommodate the increased labor
requirements.

Work done in Zambia by Ndiaye
and Sofranko (1988) illustrates the
importance of labor constraints in
farmers' decisions to adopt maize
technology. The study focused on a
sample of farmers who shifted from
traditional open-pollinated varieties
to hybrids. The authors discovered
that farmers' inability to mobilize
the additional labor required for
managing hybrids resulted in
partial adoption and compromises
in the performance of recommended
practices, such as weeding and
earthing up.


Labor (person days/mo)
240 -


 Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul
Source: MLARR survey data.

Figure 18. Seasonal labor requirements for maize and groundnuts,
Makoholi region, Zimbabwe (1985-87 averages).