PROPAGATION TECHNIQUES IN SMALL CARDAMOM
Indian Institute of Spices Research,
Cardamom Research Centre,
Appangala,
Heravanadu Post,
Madikeri 571 201, Karnataka.
Small cardamom (Elettaria
cardamomum Maton), the exquisite member of spice family, Zingiberaceae
originated in the evergreen expanse of Western Ghats .
The spice endowed with its alluring qualities is appropriately acknowledged as
“Queen of Spices”. Several varieties with superior quality traits for high
yield, resistant to pests and diseases have been evolved through selection and
hybridization process and being widely accepted among the farming community
across the cardamom growing regions. Effective transfer of these desirable
traits to the next generation without any dilution of the genetic fidelity and
also to produce ample quantity of quality planting materials to cater needs of the
farmers, appropriate methods of propagation need to be adopted. Cardamom is
generally propagated by seeds and suckers (vegetative/clonal propagation). However,
being a cross pollinated crop, considerable variation is observed in the
seedling progenies and the seedlings may not possess all the qualities of the
mother plant. Hence, vegetative propagation is normally adopted for mass multiplication
of elite clones and also to maintain the genetic purity.
Seed propagation
Different
steps involved in raising nurseries using seed material are given below:
Primary nursery
Selection of nursery site:
Selection of seeds:
Seeds
should be collected from vigorously growing high yielding plants with well
formed compact panicles and well ripened capsules. The plants should be free
from the infestation of pests and diseases. Number of flowering branches produced
on the panicles, percentage of fruit set and number of seeds per capsule are
given due consideration while selecting the mother plants for collection of
seed material. Apart from these desirable attributes, the mother clump should also
have more number of tillers (shoots) per plant. On an average, one kg fruits
contain 900-1000 capsules and 10-15 seeds per capsule. On an average, one kg of
seed capsules is required to produce 3000-5000 seedlings and half kg seed
capsules are sufficient to produce seedlings for an area of one acre. Seeds are
collected from fully ripened capsules, preferably from second or third round of
harvest during September. The seeds are either washed in water and sown
immediately or mixed with wood ash and dried for two to nine days before sowing.
Immediate sowing of seeds produces good results and is also the widely accepted
method. After harvesting, the extracted seeds are immersed in water to separate
immature and degenerated seeds. The seeds are then thoroughly washed with water
to remove mucilaginous coating covering the seeds. After draining out water,
the seeds are mixed with wood ash and dried under shade.
The seeds which are sown immediately after harvest germinate early and uniformly. The seedlings will be ready for transplanting 10 months after sowing. The ideal sowing season is reported to be November - January for Kerala and Tamil Nadu and September for Karnataka.
Pre-sowing treatments of seeds:
Cardamom
seeds posses a hard seed coat, which delays its germination. Studies have been
undertaken to evaluate the effect of pre-sowing treatments to enhance
germination percentage (Table 1).
Table 1.
|
Effect of acid treatment on seed germination of cardamom
|
||
Treatment
|
Mode
|
Duration
|
Germination percentage
(increase or decrease over control)
|
Con. Nitric acid
|
Soaking
|
five minutes
|
nine per cent increase
|
Conc. Hydrochloric acid
|
Soaking
|
five minutes
|
Increased germination
|
25 per cent Nitric acid
|
Soaking
|
10 minutes
|
55 per cent increase (fresh
seeds) 25 per cent increase (six to eight months old seeds)
|
25 per cent Acetic acid 25 per
cent Hydrochloric acid 25 per cent Nitric acid
|
Soaking
|
10 minutes
|
90 per cent germination
|
Acetone
|
Soaking
|
10 minutes
|
Increased germination
|
Soaking cardamom
seeds in dilute or concentrated acids for 5-10 minutes increases the
germination percentage to a considerable extent. In addition, soaking seeds in solutions
of gibberelic acid (GA3) and ethrel enhances germination
significantly.
Apart from other
factors, ambient temperature plays a vital role in germination process. Prevalence
of low temperature in the cardamom growing areas reduces germination as well as
delays the process of germination. In general, cardamom seeds fail to germinate
at temperatures lower than 15oC and greater than 35oC. The
ambient temperature prevailing during the months of September to October
favours germination of the seeds.
Sowing
Fig. 1 - Primary nursery in raised beds under protective overhead shade net
On the beds, the seeds are sown in lines usually not more than one cm deep. Rows are spread at 10 cm apart and seeds are sown one to two cm apart within a row. Deep sowing should be avoided for better and quicker germination. Seed rate of 30 to 50 grams may be adopted for 6x1 meters size bed. After sowing, the beds are covered with a thin layer of sand and then with mulch materials such as dried leaves/grass or paddy straw. Supporting twigs are laid across the bed to avoid contact of mulch materials with the soil. The beds are irrigated at regular intervals to maintain adequate moisture. Germination commences in about 20-25 days after sowing, which may continue for a month or two. The mulch materials are removed soon after the commencement of germination. The young seedlings are protected from exposure to direct sunlight and rain by providing overhead pandals (Fig. 1).
Mulching of beds
Mulching
seedbeds with appropriate materials influence germination of the seeds. Paddy
straw and dry leaves are considered as ideal mulch materials. Besides these materials,
mulching with coconut coir dust, paddy straw or goose berry leaves is also reported
to enhance the germination.
Generally two
methods viz., bed and poly bag are
adopted to raise seedlings in secondary nurseries.
The beds are
prepared as described in primary nursery. A layer of cattle manure is spread over
the bed and thoroughly mixed with soil. Seedlings of four to five leaf stages
from the primary nursery beds are transplanted in the secondary nursery at a
distance of 20 to 25cm. In Karnataka, where seeds are sown during
August-September, transplanting is normally undertaken during November-January.
While, in Kerala and Tamil Nadu, seedlings from primary beds are transplanted
to secondary nursery beds at a spacing of 20 x 20 cm during June-July. It is
observed that, rate of seedling mortality is higher when transplanted at second
leaf stage. Nevertheless, the mortality can be minimized to a greater extent by
transplanting at four-five leaf stage.
On an average, 120 gram nitrogen, 20 gram phosphorus and 300 gram potash, 50 gram magnesium and 75gram calcium are removed from a bed planted with seedlings. To promote uniform growth, 250 gram mixture made of nine parts of NPK 17:17:17 and eight parts of zinc sulphate dissolved in 10 liters of water may be sprayed once in 15-20 days, starting one month after transplanting. It is observed that application of 45 gram N, 30 gram P2O5 and 60 gram K2O per bed of 2.5 x 1 meters size in three equal splits at an interval of 45 days results in better growth and higher number of tillers. First dose of fertilizer may be applied 30 days after transplanting in the secondary nursery. Earthing up operation should be carried out after each fertilizer application and hand weeding should be undertaken once in every 20-25 days.
It is
recommended to shift the nursery site once in two to three years to prevent
buildup of pests and diseases and also to reduce the damage caused by these
agents. However, in those areas where
such practice is not possible due to non-availability of alternate sites, the proposed
nursery area may be left fallow for a year after deep digging/ploughing. This
practice would help in exposing soil-borne pests and survival structures of
pathogens to sun, thus killing them and brings down the inoculum levels to a
considerable extent. By meticulously adopting the recommended packages, the
seedlings would be ready for transplanting in main field, 10 months after
sowing.
Fig. 2 - Secondary nursery raised polybag under rainout shelter
Polythene bags of 20x20 cm size and 100 gauge thickness with three to four holes at the bottom are used to raise seedling in poly bag nurseries. The bags are filled with jungle top soil, cowdung and sand in the ratio 3:1:1. The bags are arranged in rows of convenient length and breadth for easy management. Seedlings at four to five leaf stages are transplanted into each bag (one seedling per bag) (Fig. 2). Providing adequate space between the bags facilitates better production of tillers. The advantages of raising seedlings in poly bags are:
·
Seedlings of uniform growth and tillers are
produced.
·
Duration of the nursery can be reduced to five
to six months as against 10 to 12 months in the secondary nursery. in
·
Better establishment and growth of seedlings in
the main field.
Cardamom plants
from secondary nursery or poly bags can be transplanted to the main field
during last week of May after the receipt of pre-monsoon showers or during the
first week of June after commencement of the south west monsoon.
Vegetative propagation
Suckers from elite
clones with desirable features like high production potential and resistant to
pests as well as diseases are used for establishing plantations. Plants raised
from suckers starts bearing earlier than plants produced from seeds. The
planting material should not be collected from areas endemic to diseases,
especially the viral diseases.
Rapid clonal propagation
High yielding varieties/selections
are generally multiplied in isolated clonal nurseries (Fig. 3). Disease free high yielding
plants are selected and sub cloned for subsequent multiplication. High yielding plants free from pest and
diseases, with desirable characters like bold capsules with green colour are to
be selected from plantations and part of the clump has to be uprooted for
clonal multiplication leaving the mother clump in its original place to induce
subsequent sucker production for further use.
Fig. 3 - Clonal nursery
|
For rapid multiplication the following agro-techniques
need to be followed:
·
The planting unit should consist
of one grown up sucker (rhizome) and a young growing shoot.
·
Trenches
with 45 cm width and depth and convenient length have to be opened and filled
with jungle soil, compost and topsoil.
·
The
rhizomes (planting unit) are planted at a spacing of 1.8 x 0.6 meters in
trenches, thus accommodating 9259 plants per hectare of clonal nursery area.
·
Overhead
protection by erecting pandals, regular irrigation (once in a week during
November to May) and application of fertilizers @ 48:48:96 grams. NPK per plant
in two splits need to be practiced.
·
On
an average 32 - 42 suckers will be produced after 12 months of planting one
planting unit. Taking the barely minimum of 50 per cent of this suckers/clump, 16-21
planting units (one grown up sucker along with a growing young shoot i.e. sucker) from one mother-planting
unit after 12 months are produced.
·
Drenching
the trenches with cowdung slurry with two kg of nutrients mixture (19:19:19
NPK) mixed in 200 liters of water, further hastens production of suckers and enhances
the growth.
·
In
an area of one hectare clonal nursery, 1,48,144 to 1,94,439 planting units can
be produced after 12 months of establishment.
Major pests and diseases in nursery and management
Major diseases observed in the
nursery are leaf spots, damping off/seedling rots and leaf rots.
Primary nursery leaf spots
The disease can be contained by
undertaking the following management measures:
·
Sowing of the seeds may be undertaken during August
– September, to ensure sufficient growth of seedlings, so that they develop
tolerance to the disease.
·
Provide adequate shade by providing overhead
pandals with coir material/ mat/agro- shade nets/thatched coconut fronds.
·
Prophylactic spraying with fungicides such as mancozeb
(0.2 per cent) may be given on the leaves. First spray is to be given during
March-April, depending on the receipt of summer showers and subsequent sprays
at fortnightly intervals. Two to three rounds of spraying may be given.
·
Clipping and destructing severely affected leaves after spraying is to
be done to arrest further spread to the remaining healthy leaves.
·
Avoid raising nursery continuously in the same
site.
Secondary nursery leaf spot
In secondary
nurseries, another type of leaf spot incited by Cercospora zingiberi is of common occurrence. The disease is
characterized with the formation of yellowish to reddish brown coloured
rectangular patches on the lamina, which run parallel to the veins. In the
advanced stages, the lesions assumes muddy red colour.
Prophylactic spraying with
mancozeb (0.2 per cent) on the foliage effectively prevents the establishment and
subsequent spread of the disease.
Nursery leaf rot
Normally
seedlings of three to four months old are more vulnerable to the disease. The
disease, which is of limited occurrence in the nurseries, is caused by Fusarium sp. and Alternaria sp. The symptoms include, formation of water soaked
lesions on the leaves, which later becomes necrotic patches leading to decay of
affected areas. Usually the damage is more pronounced on the leaf tips and
distal portions of the foliage. Under favourable conditions, rotting extends to
petiole and leaf sheaths also.
Avoiding
excessive watering in the nurseries prevents initiation and further
proliferation of the disease. When the disease is noticed in the nurseries, spray
the seedlings with carbendazim (0.2 per cent) twice at 15 days interval after
destroying the affected plant parts.
Damping off or seedling rot
·
In primary nurseries, practice thin sowing to
avoid overcrowding of the seedlings.
·
Prevent water stagnation by providing adequate
drainage facilities.
·
Remove affected seedlings and maintain proper phyotsanitary
measures in the nursery.
·
When infection is noticed, drench the nursery
beds with copper oxychloride (0.2 per cent).
·
Pre-sowing treatment of seeds with antagonistic
biocontrol agents such as Trichoderma or
Pseudomonas protect the seedlings in
the early stages of growth. Application of Trichoderma
at 100 grams per square meter of the bed also helps in reducing the disease
spread.
Damping off
The disease is a
major problem in the secondary nurseries. Seedlings which have attained
maturity (six to eight months old) are more susceptible to the disease. The
disease is caused by soil-borne fungi, Pythium
vexans and Rhizoctonia solani. Another
soil-dwelling pathogen, Fusarium sp. incites
root rot in the secondary nurseries. The disease attains severity during the
monsoon season, when the soil moisture level is excess due to inadequate
drainage. The diseases initiates on the leaves as pale yellow discolouration and
withering of seedlings. Rotting or decay starts at the collar region and it also
spreads to the rhizome as well as roots. In severe cases, the collar region
breaks off and the seedlings collapse.
·
Uproot and destroy all the affected seedlings in
the nursery.
·
Avoid use of excess water for irrigation.
·
Remove mulch materials a soon as the disease is
noticed from the nursery beds and rack the soil gently.
·
Drench the nursery beds with copper oxychloride
(0.2 per cent) at the rate three to five liters per square meter. Two to three
rounds of drenching should be resorted at 15 days interval.
Cultural Practices
·
Raise nurseries away from main plantations to
reduce possibilities of infestation and reinfestation from the nearby infested plantations.
·
Provide sufficient organic fertilizers to
encourage better vegetative growth.
·
Shift nurseries repeatedly to overcome soil-
borne pest problems like root knot nematodes and root grubs.
·
Catch and destroy the beetles of root grubs using
insect nets especially in 2 season nurseries.
·
Collect the cut worms hiding in the mulch in the
affected area and destroy.
Chemical control
Insecticides
like quinalphos (0.05 per cent), fenthion (0.075 per cent) or dimethoate (0.05 per
cent) may be used to tackle the pest problem. The sprays may be undertaken at
monthly intervals starting from rapid tillering stage. In the old nursery
sites, exposed sandy loam areas and two season nurseries root knot nematode
assumes severe proportion. Apply one round of carbofuran or phorate at 30-40 g/m2
in one season nursery at rapidly tillering stage and apply two rounds of
granular insecticides to two season nurseries at three monthly intervals. Application
of granular insecticides at three monthly intervals is highly essential to
protect the underground and sub-aerial parts in clonal nurseries.
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