Environmental Engineering Reference
In-Depth Information
yams are grown on freshly cleared or already farmed lands. They are usually, but
not always, planted as the first crop in a mixed cropping system. The planting order
adopted depends on availability of planting material.
Sources of planting material
Most farmers, especially newcomers, obtain planting materials of water yam from
the market. Portions of exceptionally tasty tubers that are purchased for home
consumption are also saved for planting. Generally, farmers save the heads of
ware yams that are consumed by the farm family for replanting. A number
of farmers plant heirloom varieties. Farmer-to-farmer exchange of germplasm
also plays an important part in planting material supply.
Planting material and planting
Tuber heads or cuttings from ware yams are used as planting materials. Small
tubers generated after milking are also used as planting material. The sizes of the
yam setts vary from 200 to 250 g, but larger pieces weighing 500 g are sometimes
used. Tuber yield is usually proportional to the size of planting material. However,
in some varieties such as “matches”, very small cuttings, the size of a small match-
box, produce very large ware yams. Water yams generally sprout very easily. Even
the peeled skins of some varieties are credited with sprouting ability. They are
planted in February in areas with early rains, but are mostly planted between
March and April.
Nursery
The “sett” may be direct sown or nursed and transplanted. Where nursing is prac-
tised, the “setts” are nursed on the flat, either in a single layer, or up to three lay-
ers, and covered with dead leaves, soil, or a mixture of the two. Nursing lasts for
two to four weeks, but seedlings may be raised in the nursery for up to two
months before field transplanting.
Field planting
The yams are planted in holes on the flat, in large mounds with no planting holes
under them, or in holes which are mounded over. The planting holes range from
20 to 60 cm in diameter and are 30 to 60 cm deep. Mound sizes vary from 50 to
85 cm wide and 10 to 25 cm high. The setts are planted at 10-25 cm deep
depending upon the depth of the planting hole. In areas with less friable soils the
planting holes are mounded over. After planting, the holes or mounds are capped
with dead leaves. Very vigorous yam varieties such as
alamoa poto
are usually
planted in a hole without mounding.
Staking
Water yams are staked. Trees left
in situ
or deliberately planted serve as stakes.
Up to eight or more mounds are constructed around a single large tree. The
