these figures conceal tremendous
variability between regions, be-
tween crops, and between groups of
producers. Maize usually receives
more fertilizer than other food
crops, some of which show a low
response to added nutrients (millet,
sorghum, cassava), but less than
high-value cash crops (cotton,
tobacco).

Probably the single biggest obstacle
to fertilizer use in Africa is cost.
Nutrient-to-maize grain price ratios
(which indicate the number of
kilograms of maize grain needed to
pay for one kilogram of nitrogen)
reveal that fertilizer is relatively
more expensive in Africa than in
either Asia or Latin America,
particularly in landlocked countries
with no ready access to an ocean
port (Table 5). Relatively high
prices for fertilizer can be attrib-
uted to higher real marketing costs
(which are incurred when distribu-
tors must move fertilizer over long
distances and transportation is
poor), as well as to weak and dis-
persed demand (which prevents
distributors from capturing econo-
mies of scale). The importance of
marketing costs in Africa becomes
evident in comparing the cost of
nitrogenous fertilizers: the unit cost
of nitrogen contained in urea (46%
N) is consistently lower than that of
nitrogen contained in ammonium
sulfate (20.5% N), reflecting the
lower cost of transporting the more
concentrated formulation.

Relatively high prices do not
preclude the use of fertilizer on
maize if the yield response is high
enough to make fertilizer use prof-
itable. Trial data from sites
throughout Africa suggest that
modest doses of fertilizer-espe-
cially nitrogen-on maize often
generate significant yield increases
(Figure 15). A study carried out by
International Fertilizer Develop-
ment Center (IFDC) (1985) con-


Table 5. Nitrogen fertilizer price in relation to maize grain price,
selected countries, 1988/89


Country

Cameroon
Kenya
Malawi
Nigeria
Zambia
Zimbabwe

Turkey
India
Pakistan
Philippines
Thailand

Brazil
Chile
Mexico


Farm-level-
nitrogewr
 price
 (US$/t

 732
 1,016
 720
 1,333
 353
 711

 476
 334
 321
 469
 722

 796
 599
 250


(Farime .U

 pm.TT- M ilpggto-
 (U^ ... p. 3


Source: CIMMYT survey.


Maize grain yield (kg)
5--


0 50 100
 Nitrogen (kg)


Source: Maize Commodity Research Team, Ministry of Agriculture, Malawi.

Figure 15. Maize yield response to nitrogen fertilizer on estate and
smallholder farms, Malawi.