Environmental Engineering Reference
In-Depth Information
generate income from them. Some cultivars such as
afasew bore
are used for spe-
cial festivals. The yields of water yams are exceptionally high. The tubers are
commonly boiled for
ampesi
or made into porridge. Some cultivars are also suit-
able for roasting.
White yam (D. rotundata)
Ecology
The white yams are predominantly grown in home garden agroforestry systems.
They are also cultivated as part of annual cropping and agroforestry non-home gar-
den systems. The crop is grown between February and March, but may be planted
as early as January or late in April.
Land preparation
White yams are planted on freshly cleared or on previously cultivated lands as a
first crop in a mixed cropping system or after other crops. The planting material
is grown in holes on the flat, in mounds, or in holes over which mounds are made.
Planting
Heads, cuttings, or small whole tubers are used. Sett size ranges from 250
to 500 g, but as much as 1-2 kg setts may be used. The depth of the planting
hole ranges between 30 and 50 cm with a diameter of 30 cm to over 50 cm.
The sett is placed 10-30 cm deep in the planting hole depending upon the sett
size and the vigour of the cultivars. Mound sizes ranging from 10
55 cm
to 15 cm
55 cm are formed over the planting holes depending upon soil
structure and the vigour of the variety. No special order is followed in the
planting of white yam in a mixed cropping system. In a few cases shallow-
rooted, compact crops such as groundnuts or some vegetables like shallots
are planted on the mounds. The planting material is sometimes nursed for one
to four weeks prior to field planting.
Staking
The staking technique is as outlined for the bush yam and water yam. The distance
from the live tree stake to the base of the leader ranges from 70 cm to over 120 cm.
The vines are trained along the leader stakes when they are 60-100 cm long. Vine
length may sometimes reach 150 cm before staking.
Harvesting and storage
Tubers mature five to six months after planting but are harvested at seven to eight
months after planting. Tuber sizes may vary between 30 cm to over 40 cm. The
harvested tubers are stored in a hole covered with leaves or soil, tied to poles, or
stored in barns for a period of four to 12 months.
