IITA agroecological zones-
Within its mandate area, IITA dis-
tinguishes three broad agroecologi-
cal zones: the forest, the moist (or
Guinea) savanna, and the forest/
savanna transition zone (IITA
1988). This classification is based
primarily on differences in vegeta-
tion-strikingly evident as one
moves northward from the coast-
which in turn reflect differences in
soil conditions, climate, and human
activity (Map 2).

The three broad agroecological
zones are subdivided into five
maize production zones (Table 2):

 Humid forest: Located in the
 southern part of the forest zone,
 the humid forest production
 zone experiences more than
 seven humid months (i.e.,
 months in which precipitation
 exceeds potential evapotranspi-
 ration). Rainfall is distributed
 unimodally or bimodally. Soils
 are acidic.


 Maize production zones

 Humid forest

 I I Semideciduous forest and forest-savanna
 transition

 S Derived/southern and northern Guinea
 savanna

 S Midaltitude

Source: Adapted from IITA (1988).

Map 2. Maize production zones, western and central Africa


Table 2. IITA Maize-growing zones for western coastal and central Africa


Zone


Humid forest
(Southern forest)

Semideciduous
forest
(Northern forest)

Derived and
southern Guinea
savannas

Northern Guinea
savanna

Midaltitude
(Savanna vegetation)


Annual
rainfall
(mm)

>1,400

 1,250
 -1,400


1,100
-1,400

 900
 -100


 1.100
 1.600


 Rainfall Soil
distribution types


Unimodal

Bimodal


Climax Crops planted
vegetation with maize


Ultisol, Evergreen
oxisol forest


Alfisol


UnimodalM Alfaol,
bimodal ultisa


Unimodal


Ummodal


Semideciduous
forest


Cassava,
plantain

Cassava


Wosannd yam
savanna yafl


AlftsP~ Shub --S~n
 firP-ealataaL.


Other major crops


Oil palm,
rubber

Cocoa,
oil palm

Tobacco,
cotton

Cotton


Soroigmn,
mille .-
~ararn~ es


ltisdL mhi mL cocoi
ulti"L. waidb ".i~


Coffee


Source: IITA. .... .... ........... ... ... ...
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