| Cultivation
Soil
It thrives best in porous
and wall-drained soils with a pH ranging
form 5.5 t0 7. it dose not require very
fertile soils and can be economically be
grown on soils of Karnataka are ideal for
the cultivation of this crop.
Climate
Coleus is a crop of
the tropics and is found growing well on
barren hills at an altitude of about 2400m,
under tropical and subtropical conditions.
In India, it is grown mainly in Belgaum
(the Sahayadri mountain range of Karnataka)
and in Gujarat. The Climate here is humid
with a RH ranging from 83 to 95% and a temperature
of 10-25o C. The annual rainfalls in 100-160
cm, mainly between June-September. It is
also found to performs well in less humid
and warmer regions of South India like Coimbatora,
where it is grown as an irrigated crop.
Propagation
Coleus can be propagated
by seeds as well as by stem-cuttings. However,
propagation through seeds is little difficult
and slow and should be used only for the
breeding of new varieties. Whereas, propagation
by cuttings is very easy and economical
to raise this crops on large scale.
Nursery
Raising
The viability of the seeds being very poor
(8-10%) a sufficient quantity of fresh seeds
has to be sown in well prepared nursery-beds
to obtain good germination. Regular care
about watering, weeding and plant protection
of the nursery should be taken. In about
15 to 20 days, the germination is completed.
When the seedling are 45 days old and have
attained about 8-10 cm height, they are
ready for transplanting.
Vegetative
Propagation
Vegetatively, the crop is propagated through
terminal cuttings. Normally, 10-12 cm-long
cuttings, comprising of 3-4 pairs of leaves,
are sown in already prepared nursery-beds
and regular care about shading and watering
is taken. The cuttings establish well in
the nurseries and there is no problem in
their rooting. After about a month’s
time, when the cuttings have produced sufficient
roots, they are transplanted to the main
field.
Planting
In most areas, the crop is planted during
June-July at the onset of the Southwest
monsoon. Before planting, the field is ploughed
deep soon after the of pre-monsoon showers
and furrows at a spacing of 60 cm and the
rooted cuttings or seedlings are planted
20 cm apart within the row.
Manures
and Fertilizers
Studies conducted at TNAU. Coimbatora, to
standardize the nutritional requirement
of this crop have shown that it responds
well to the application of N.P. and K.A.
combination of 40 kg N. 60 kg P2O5 and 50
Kg KO2 has was found to be optimum for obtaining
the maximum fresh (120t/ha) and dry (3.982
t/ha) tuber yield from this crop Half the
dose of N, the whole P and whole K may be
applied as the basal dose after planting
as top-dressing.
Irrigation
The first irrigation is given immediately
after transplanting, if there are no rains,
During the first two weeks after planting,
the crop is irrigated once in three days
and thereafter, weekly irrigation is enough
to obtain good growth and yield.
Weeding
Due to the frequent irrigations during the
initial stages, there is a lot of competition
from weeks. In order to obtain economic
yield, frequent weeding during the early
growth period is desirable.
Pest
and Diseases
The leaf-eating caterpillars, mealy bugs
and root knot nematodes are the important
pests that attack this crop. These insects
can be controlled by spraying the plants
and drenching their roots with 0.1% menthyl
parathion, while nematodes can be controlled
by the application of carbofuran granules
at the rate of 20 kg/ha.
Diseases
Among the disease, bacterial wilt is the
major one. The spread of wit can be controlled
by spraying and drenching the soil adjoining
the affected plants with 0.2% Captan solution
immediately after the appearance of the
disease and later after a week’s interval.
Harvesting
and Yield
Flowers, if any should be nipped off during
the growing period to obtain more biomass
of roots. The crop is ready for harvest
41/2 to 5 months after planting. The plants
are loosened, uprooted, the tubers separated,
cleaned and sun-dried for the extraction
of “forskolin”.
On an average, a yield of
1500-2000 kg/ha of dry tubers may be obtained.
However, if proper cultivation practices
are applied, a yield of up to 2500 kg/ha.
of dry tubers can be easily obtained. |
