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TUBER INFORMATION
GREATER YAM (Dioscorea alata)
Dioscorea
alata is predominantly a tropical plant. The crop cannot
withstand frost and excessively high temperatures. Temperature
around 30ºC and rainfall of 120-200 cm distributed
throughout the growth period are ideal. Day length greater
than 12 hours during initial stages and shorter day length
during the later part of the growing season favour satisfactory
tuber formation. Yam requires loose, deep, well-drained,
fertile soil. The crop does not come up well in waterlogged
conditions.
Season
Seed
tubers are normally planted during the later part of
the dry season (March-April) and start sprouting with
the onset of pre-monsoon showers. If the planting is
delayed, yams start sprouting in storage, which is not
desirable for planting.
1.
Sree Keerthi: Suitable for intercropping in mature
coconut garden and with banana.
2. Sree Roopa: Possesses excellent cooking quality.
3. Indu: This is recommended as a pure crop and also
as an intercrop of coconut in the reclaimed alluvial
soils of Kuttanad.
4. Sree Shilpa: This is the first hybrid having good
culinary quality. The crop matures early, within 8
months. The tubers have 33-35% dry matter, 17-19%
starch, 1.4-2% protein and 0.8-1.2% sugar.
Top...
Seeds
and sowing
D.
alata produces mostly a single big tuber in which only
one head end of the tuber is available as good seed material.
For getting the head end in each propagation unit, the
whole tuber is divided longitudinally. Each piece of cut
tuber should weigh at least 250-300 g. Dip the pieces
in cowdung slurry and allow to dry under the shade before
planting. About 2500-3000 kg of seed material is required
to cover one hectare of land.
Preparation
of land
Plough
or dig the land up to a depth of 15-20 cm. Dig pits
of size 45 x 45 x 45 cm at a distance of 1 x 1m. Fill
up three fourth of the pits with 1-1.25 kg cattle manure
or compost and mix with topsoil. Plant the cut tuber
pieces and completely cover the pit with leafy materials
to conserve soil moisture and maintain optimum temperature.
Trailing
Trailing
is essential to expose the leaves to sunlight. Trailing
has to be done within 15 days after sprouting by coir
rope attached to artificial supports in the open areas
or to trees where they are raised as an intercrop. When
grown in open areas, trail to a height of 3-4 m. Trail
the vines properly as and when side shoots are produced.
Ensure
sufficient moisture in the soil at the time of planting.
For uniform sprouting, irrigate just after planting and
one week later. Subsequent irrigation may be given at
12-15 days intervals, depending on the moisture retention
capacity of the soil. The irrigation should be stopped
3-4 weeks before harvest. About 9-12 irrigations are required
for the crop till harvest. In the case of rainfed crop,
if there is prolonged drought, supplementary irrigation
is required.
Apply
cattle manure or compost at 10-15 t/ha as basal dressing.
A fertilizer dose of 80:60:80 kg of N:P2O5:K2O per ha
has to be applied in two splits; half dose of N, full
P2O5 and half of K2O within a week after sprouting; remaining
half N and half K2O one month after the first application
along with weeding and earthing up.
Yam
scale is found to infest the corms both under field and
storage situations. As a prophylactic measure, dip the
planting material in monocrotophos 0.05% suspension for
10 minutes.
The
crop becomes ready for harvest within 8-9 months after
planting when the vines are completely dried up. Dig out
the tubers without causing injury
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