Environmental Engineering Reference
In-Depth Information
or buried deep, a chisel is used for digging the soil around the tubers. In the case
of extremely long yams, the farmer may dig a large and deep hole near the tuber
being harvested and stand in the hole in order to reach the tuber more easily
without straining the back. To harvest very long tubers, an alternative strategy
adopted by farmers is to first remove the soil around the head of the tuber. A
branch from a nearby tree is then bent down and the tuber is tied to the branch
with the aid of a twine. The hole around the tuber is then filled with water
overnight. The water softens the soil around the tuber, and the force in the bent
branch then pulls the tuber out.
Tuber sizes
Tubers vary between 30 cm and over 50 cm in length. Some varieties are very
long, measuring over 90-120 cm, e.g. the variety
aku
.
Storage
The bush yams are usually kept in the field, and tubers are detached from the
plants as required. Harvested tubers have a shelf life of only a few days, after
which the cooking quality deteriorates rapidly. They are therefore kept for only
one to three days to a maximum of one week. One variety,
kookooase fitaa
is
reported to be storable for six months to one year.
Uses
Bush yams are valued for their palatability and food security value. Some
cultivars are also used for special celebrations. They are predominantly used in
the preparation of the
ampesi
dish (boiled starchy staple served with stews or
sauce) or pounded in
fufu
.
Maintenance strategies
Farmers maintain the crop by
in-situ
conservation. The harvesting is staggered.
Tubers are harvested from the standing crop as needed during the harvesting sea-
son. The tubers are sometimes left in the holes to sprout and produce new growth
during the growing season. Subsequently they produce even heavier yields. In
addition to managing the plants as perennials, fresh plantings are made yearly.
Also, farmers maintain sexual seeds that drop, sprout, and produce many volun-
teer plants.
Greater or water yam (D. alata)
Ecology
Greater or water yams do better under full exposure to sunlight. The greater yams
are normally grown in home garden agroforestry or annual cropping systems. They
also occur in a very few agroforestry non-home garden land-use systems. Water
