Environmental Engineering Reference
In-Depth Information
7
Yams: Traditional ways of managing
their diversity for food security in
southern Ghana
Essie T. Blay
Introduction
Ya m s (
Dioscorea
spp.) occur throughout the tropics. At least seven wild species exist
in West Africa but six main types are cultivated. The cultivated ones are white yam
or eight-month yam (
D. rotundata
), yellow yam or 12-month yam (
D. cayenensis
),
greater or water yam (
D. alata
), lesser or Chinese yam (
D. esculenta
), bulbil-bearing
yam or air potato (
D. bulbifera
), and trifoliate, cluster, or bitter yam (
D. dumetorum
)
(Irvine, 1979; Degras, 1993; Blay, 2002; Kranjac-Berisavljevic and Gandaa, 2002;
see also Chapters 8 and 17; Plates 9-11).
The transitional and northern savanna regions constitute the centre for commer-
cial yam production in Ghana (see Chapter 8; Map B). The cultivation of yams in
Ghana is concentrated around Northern, Ashanti, Brong Ahafo, Volta, and Upper
West regions (Abbiw, 1990). However, the crop is grown throughout the country
both as a commercial and a subsistence crop. The tubers are a rich source of vita-
min C, potassium, phosphorus, and protein (4-8 per cent of fresh weight). Yam is
regarded as a prestigious food in many communities in Ghana. The tubers are
served boiled, fried, baked, or roasted, or prepared into porridge similar to Irish
stew. Certain yam dishes, notably
tc
(Akan-Twi word for a mashed yam prepar-
ation), are used in several local customs and celebrations.
Major festivals are woven around yam harvest. In some of the major yam-
growing areas in Ghana, prescribed rites must be performed at the beginning of
the harvest season before the tubers are released for consumption. Yam is also
an important food security crop. Some yam varieties have a very long shelf life
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