Root Trainer planting technique for
Hevea
The introduction
and establishment of rubber tree and the development of rubber plantation
industry in India is one of the most remarkable success stories in the Indian
plantation sector. In India, rubber was
first received in 1878, from Sri Lanka. Rubber cultivation in an organized
scale was initiated in India in Kerala (Travancore) in 1902. In the early years
of rubber cultivation, assorted seeds collected indiscriminately used as the planting
material. Naturally, productivity was
very poor. Subsequently improved seeds
from selected high yielding mother plants were used. However since Hevea is a highly
heterozygous crop, seed propagation has the inherent drawback of
creating very high variation for growth, vigour and yield between individual
trees in the plantations. This limitation was overcome by the successful
introduction of bud-grafting, which has proved to be a breakthrough in
enhancing the production and productivity of rubber plantation industry. With
the perfection of the bud-grafting method by Van Helten in 1917, in
collaboration with two planters Bodde and Tass (Djikman, 1951), the crop began
to be propagated almost exclusively by cloning a few high yielding trees. This
method was widely accepted and is in practice for the past several decades for
multiplication of high yielding clones. The budded plants can be either
directly planted in the field or first established in polythene bags and
transplant at an advanced stage. Rubber Board started promoting
polybag-planting technique during 1980s. Compared to direct planting of budded
stumps, planting polybag plants have several advantages like facility to cull
out weaklings in the nursery itself, more uniformity in growth, less casualty
due to planting shock, reduced immaturity period etc.
However, in spite of various advantages,
polybag plants were reported to have a few drawbacks, coiling of tap root being
the most important among them. A coiled tap root will never attain its normal
growth and leads to root strangling and distortion in subsequent years. Coiling
of tap root was reported to affect adversely was reported to affect wind
fastness and drought tolerance in several tree crops (Wilson, 1986, Sharma,
1987, Josiah and Jones 1992, Anon.1999). In rubber, lateral roots grow
horizontally, confined to a depth up to 30 cm in the top soil. In polybags the
laterals grow circularly within the bag. Moreover, polybag planting technique
is labour intensive and the heavy polybags are quite inconvenient to handle in
the nursery, transport to the field and transplanting. Root trainer planting
technique was standardized to overcome the above mentioned drawbacks of polybag
plants.
Root trainer
containers
The
structure and shape of root trainer containers are scientifically designed and
fabricated to ensure proper growth and orientation of roots. Made of
polypropylene, the root trainer containers are tapering in shape from the top
downwards and end up in a drainage hole at the bottom. The inside wall of the
container is provided with some ridges arranged length-wise which end near the
drainage hole at the bottom. (Fig. 1). Root trainers of different holding
capacity varying from 50 cc to 1000 cc are available in the market. For seed
propagated crops like teak, cashew, apple, walnut etc. smaller containers (100
cc to 200 cc) are sufficient, but rubber requires larger containers sufficient
enough to accommodate the lengthy tap root of budded stumps. Green budded
stumps could be planted in root trainers of length 26 cm with a holding
capacity of 600 cc; whereas brown budded stumps require still larger containers
of length 30 cm with a holding capacity of 800 cc.
Potting medium
Availability
of a good potting medium is very important in root trainer planting technique.
A good potting medium is reported to have certain qualities like light weight,
friability, low bulk density, good drainage and porosity, good water holding
capacity, easy blendability, no inherent fertility, slight acidity and should
be free from fungal spores, insects, weed seeds etc. (Chakrabarti et al. 1998).
Top soil used to fill polybags possess none of the above characteristics of a
good potting medium and this has been suggested as the main reason for the poor
development of lateral roots in polybags (Josiah and Jones 1992, Khedkhar and
Subramanian, 1995).
Sphagnum moss (peat moss) is an excellent potting medium due to its
inherent water holding capacity. Since
it is not locally available, importing sphagnum peat for commercial purpose is
not practicable due to the cost factor involved. A number of alternative media
have been suggested like saw dust, rice husk (Shrivastava et al., 1998),
sugarcane waste (Aminah Hamzah, 2000), compost (Ginwal et al, 2001), biogas
slurry (Josiah and Jones, 1992) etc. but none of them were found to be suitable
as a potting medium in rubber nursery, due to various reasons. However, cured
coir pith possesses most of the characters of a good potting medium and was
found to be ideal to fill the root trainers as suggested by World Bank (Josiah
and Jones 1992). In countries where coconut is not available, World Bank has
even suggested to import coconut as an oil seed so that coir pith could be made
available as a byproduct. Fortunately, coir pith is available in plenty in most
of the costal Districts in Kerala and Kanyakumari District of Tamil Nadu. Being
a waste byproduct of coir industry, easy availability of this renewable source
of good potting medium is the most important factor, which promoted the
successful standardization of root trainer planting technique for rubber.
Raw coir pith available in the coir factories contains large quantities
of coir fibers, which could easily be removed by passing through a wire mesh
used for sieving sand in building industry. Coir pith also contains certain
chemicals like phenol, tannin, chitin etc. These chemicals have an inhibitory
effect on root growth. There fore, it is essential to remove these chemicals
completely before the coir pith is used as a potting medium. Most of these
chemicals could be removed by keeping the coir pith immersed in water for a
minimum period of one month. Change of water once or twice is also recommended.
After one month, the excess water is squeezed out and the cured coir pith is
partially dried under shade.
Conventionally, coconut husk is cured in
water for about one year before coir extraction and hence 90% of the harmful
chemicals would be lost during the curing process. The remaining chemicals are
removed by immersing in water before the coir pith is used as a potting medium.
But, in Tamil Nadu and some parts of Kerala coir is extracted from raw husk
(without curing) and such coir pith is not suitable to use as a potting medium.
This raw coir pith requires curing in water minimum for a period of one year
with frequent change of water to remove the harmful chemical constituents.
Filling root trainers
Coir pith is
an inert material devoid of any nutrients and hence it has to be enriched by
mixing 250 grams each of powdered rock phosphate, neem cake and bone meal per
one basket (approximately 20 kg) of coir pith. Then 5g each of a fungicide
(Dithane M-45 or Indophil M-45) and a pesticide (Malathione) are also added and
thoroughly mixed with the coir pith. This mixture is used to fill the containers
after placing one iron rod having
the diameter and length of a small budded stump in the middle of the container.
It is very important to fill the container tightly with coir pith because loose
coir pith will break and damage the root system when the root plug is separated
from the container for transplanting to the field. Special attention is
required for tight filling at the bottom ¼ of the container as this region is
highly vulnerable to breakage. A space of approximately 3 cm is kept unfilled
at the top of the container to facilitate irrigation. Once the filling is
completed the rod placed at the middle of the container is removed carefully so
that a hole is formed through out the
entire length of the soil core inside the container. This central hole
functions as drainage of excess water and also facilitates aeration inside the
container. Failure to provide this central hole may result in water logging
leading to serious damage to the roots.
Planting budded stumps
Green budded stumps are preferred for planting in root trainers. Medium
sized brown budded stumps up to one year of growth could also be used provided
the stumps are of moderate size while large budded stumps of more than one year
of growth are not suitable for this planting technique. Green budded stumps are
usually planted in root trainers of length 26 cm having a holding capacity of
600 cc. Brown budded stumps require bigger root trainers of length 30 cm with a
holding capacity of 800 cc (Fig. 2).
Successful bud-grafts are pulled out and the taproot is pruned
proportionate to the length of the container. Lateral roots are also removed,
but the laterals at the collar region are retained up to 2.5 cm. A small
portion of coir pith is removed from the top and the tap root is inserted
through the hole provided length-wise at the centre of the soil core. In case
of larger roots the central hole is widened with the help of a stick of
appropriate size. Since excess pressure may damage skin of the root and the
stump may fail to sprout. After planting
the budded stump, the coir pith removed from the top of the container is
replaced keeping the pruned laterals in place. Tap root may be pruned further
if the bottom tip is found protruding through the drainage hole at the bottom of
the container.
After planting budded stumps, the root trainers are stacked in stands
made of any materials like iron rods, bamboo splints, wooden reapers etc. The
frame for the stand as shown in the figure (Fig. 3) is made with four iron rods
of length 120 cm each. The space in between the rods is so adjusted to hang the
containers freely in between the rods.
These rods are welded together with the help of two smaller rods of 30
cm length at the end. This frame is then fixed on four legs (wooden or iron) of
height 18 cm above the ground level. In this stand 24 root trainers can be
conveniently stacked in two rows of 12 each with a space of about 7.5 cm in
between.
The tap root of the plant
inside the root trainer, arranged in
the stand, off the ground, resumes growth, within a few days and undergoes air
pruning on growing in to air through the drainage hole at the bottom of the
container. Simultaneously, bud break also takes place and the shoot grows very
actively. In addition to the NPKMg
supplied as 2% solution (explained elsewhere) the actively growing plant
requires a number of micro/trace elements also for its healthy growth. Since
neither the potting mixture nor the air pruned roots could satisfy this
fertilizer requirement, the plant will undergo a set back in its initial growth
phase. In order to avoid this negative influence on the growth the root
trainers are covered with top soil up to about 25% of the bottom portion of the
container (Fig. 4) and the roots are permitted to grow in to the soil till the
plants attain two whorls of growth.
Alternatively, the root trainers could also be stacked in trenches taken
in soil. Trenches cut to a width and depth of 30 cm each is half filled with
fertile top soil mixed with compost or cow dung. Root trainers are stacked in
this half filled trenches in two rows keeping a distance of 7.5 cm between
plants in a line and 15 cm between two lines in a trench. After arranging the root trainers, the
remaining portion of the trench is also filled with top soil. Care has to be taken not to block the
drainage hole at the bottom of the container. As in the previous case, the
plants are grown in the trench till they attain two whorls of leaves.
Sufficient space in between the stand/trench is necessary to facilitate
cultural operations. Root trainers are stacked in the stand/trench in such a
way that the bud patch faces the space left in between the stand/trench.
Irrigation
In order to
ensure an optimum growth and vigour, judicious irrigation is a very important
cultural operation in the root trainer nursery. After planting budded stumps,
the root trainers are well irrigated till the entire potting medium is
saturated. Daily irrigation is recommended till the first whorl of leaves
attain maturity, and thereafter irrigation could be reduced to alternate daily.
Water logging should be avoided under any circumstance. If water is not drained
out even 2-3 hours after irrigation, it could be due to a block in the drainage
hole, which has to be cleared immediately, and proper drainage of water
ensured. Water logging even for a period of one week can cause irreparable
damage to the root system and the plant may dry up. In case of a moderate rain,
irrigation could be skipped for 2-3 days. In summer season, the soil in which
the root trainers are stacked should also be drenched with water once or twice
a week.
Fertilizer application
Manuring is another step, which warrants utmost care in the root
trainer nursery, since the potting medium is an inert material. Fertilization
is done with the same mixture of NPKMg (10:10:4:1.5) as recommended for polybag
plants, but the method of application is different. For a polybag plant in the nursery,
10 g of the above mixture is recommended for the first month, 20 g in the
second month, 30 g in the third month and 40 g each in the remaining months, A
polybag contains 8-10 kg of top soil, but the quantity of potting mixture
contained in a root trainer is only 220 to 400 g (depending on the size of the
container). So, based on the quantity of potting mixture, the fertilizer
requirement for a root trainer plant in the nursery is worked out as
approximately 250 to 500 mg in the initial month, 500 mg to 1 g in the second
month, 750 mg to 1.5 g in the third month and 1-2 g each in the remaining
months in the nursery. Since it is not practicable to weigh such small
quantities of fertilizer, the chances for over fertilization are very high.
Even 1 g of the fertilizer applied in the initial month may spoil the plant due
to the toxic effect of the chemical fertilizer. So, in due consideration of
these practical difficulties, chemical fertilizer is applied to root trainer
plants as a 2% solution (2 kg in 100 lit of water) of NPKMg (10:10:4:1.5) at
weekly intervals at the rate of 70 – 100 ml/plant. One liter of the above
solution is sufficient to apply to 10-15 root trainer plants. The fertilizer
schedule to prepare 10 kg of the mixture NPKMg (10:10:4:1.5) is given below,
|
Ingredients
|
Quantity (kg)
|
Analysis of the mixture (%)
|
|||
|
N
|
P2O5
|
K2O
|
MgO
|
||
|
Urea
Super phosphate
Muriate of potash
Magnesite
Soil (Filler)
|
2.2
6.4
3.5
2.0
3.5
|
10
|
10
|
4
|
1.5
|
|
|
10
|
10
|
10
|
4
|
1.5
|
Two percent is the maximum tolerance
level of plants to chemical fertilizers; a further increase in concentration
may prove to be lethal. So, it is very important to ensure that the entire
fertilizer is dissolved in water before it is applied to the plant. Any
un-dissolved fertilizer remaining at the bottom of the vessel may lead to very
high concentration of the solution at the bottom. Therefore, it is recommended to take the
required quantity of chemical fertilizer in a smaller vessel, dissolve and add
to the dilution tank by passing through a filter. The additional labour
requirement for fertilizer application could be saved if water for irrigation is substituted with the
fertilizer solution at weekly intervals.
In addition to NPKMg fertilizer, the
plants grown in containers require a number of micro/trace elements also for
their balanced and healthy growth. It is not practically possible to make
available all these micro/trace elements artificially. The Tamil Nadu
Agricultural University has developed a bio-fertilizer called ‘plant tonic’
capable of supplying most of the micro/trace elements required by containerized
plants. This fertilizer solution is prepared by dissolving 50 kg of fresh cow
dung in 50 lit of cattle urine (farmyard waste water) and this mixture is kept
for 60 days in a tank for fermentation with occasional stirring. After two
months, the mixture is filtered and the filtrate stored in a vessel as stock
solution. At the time of application, this solution is diluted five times its
volume with water and applied to containerized plants as foliar spray at
fortnightly intervals. Root trainer plants sprayed with this plant tonic was
noticed to grow very healthy with dark green leaves. Therefore it is desirable
to adopt this simple and cost effective practice to ensure healthy growth of
plants in root trainer nursery.
Shading
Quantity of potting medium contained in root trainers is much less
compared to that in polybags. Hence, it is very important to maintain the
moisture level in root trainers always at a high level. Excess loss of moisture
directly from the upper surface of the potting medium or indirectly from the
plant should be controlled by providing an overhead shade with appropriate
materials like shade net, coir mat and coconut fronds to provide about 50%
shade. Sides may be kept open to facilitate air circulation (closed sides may
build up humidity inside the nursery leading to heavy incidence of leaf
diseases). The shade may be removed completely during the onset of rainy
season.
Disease control
Shoot rot
caused by Phytophthora s. and powdery
mildew due to Oidium heveae are the
two main diseases encountered in the root trainer nursery. Phytophthora could effectively be controlled by spraying 1%
solution of Bordeaux mixture or 0.125% copper oxychloride just before the onset
of South West monsoon and during the sunny days in between rainy days. Oidium infection occurs on newly formed
tender leaves. Repeated spraying with 0.2% solution (2.5 grams in 1 lit of water)
of wettable sulphur and Bavistin (1 gr in 1 lit of water) in alternate weeks
was found to be very effective to control Oidium
infection in root trainer nursery.
Cured coir pith is attracted by termites and hence special attention is
required to control termite attack . The entire potting medium should be
drenched with 0.1% solution of chlorpyriphos before planting budded stumps and
thereafter repeated at least once in a month. In places where there is severe attack by termites, fortnightly to weekly
application is recommended. Chlorpyriphos
is available under various trade names in the market like Tataben,
Classic, Dursban, Cyphos etc. which has to be
diluted at the rate of 5 g in 1 lit of water and applied
in the nursery. If severe infection with mealy bug or scale insect is
observed malathione at a concentration of 0.1% (2 ml per liter of water) is
sprayed to keep them under check.
Hardening
Given proper care in the nursery, root trainer plants will present
better growth and vigour than polybag plants. On transplanting to the field,
the young polybag plants may be subjected to various stresses like root damage
due to transplanting, shock due to sudden exposure to unprotected open
environment, soil moisture stress due to a delay in rain etc. In the root
trainer technology, hardening is a pre-planting cultural operation by which the
plants are made capable of facing such unexpected stress situations, which may
occur on transplanting to the field.
For hardening, the soil under the root trainers are removed and the
roots outgrown the drainage hole in to the ground soil is carefully pruned with
a knife. This has to be done as early as possible on the plants attaining two
whorls of leaves, because a further delay may lead to excessive growth of roots
in to the ground soil. Sudden loss of a
large number of roots may delay the recovery
process after the plants are transferred to the stand for hardening.
The root trainer plants are
maintained in the stand, off the ground, for a minimum period of eight weeks.
If irrigation is done daily and manuring is continued with 2% solution of NPKMg
(10:10:4:1.5), at weekly intervals, an additional whorl of leaves will emerge
within 4 to 6 weeks after arranging the plants for hardening. But, the plants
could also be maintained at 2-whorls stage indefinitely, if irrigation is
restricted to biweekly intervals and manuring is reduced to only 1% solution of
urea at fortnightly intervals. An over head shade is essential at the hardening
stage and other plant protective measures like spraying, dusting etc. should be
continued till the plants are transplanted to the field.
In polybag planting technique, growth and development of the shoot
system is given importance while the development of the root system remains
neglected. On the other hand, root trainers are designed and fabricated to
ensure proper growth and development of the entire root system and hence the
name root trainer planting technique. Root trainer planting technique is based on
the principle that a well developed and properly oriented root system will
ensure better growth and performance of plants after transplanting to the
field.
Anchorage is the major function of tap root, while lateral roots are
mainly responsible for absorption of water and minerals from the soil. The
tap root of rubber has the
potential to grow up to a few meters
deep in to soil. But due to the limited
space available in the polybag, the tap root undergoes coiling at 30- 45 cm
length. This coiled tap root was observed not to attain its normal growth even several years
after transplanting to the field (Fig. 5). On the other hand, during the
process of hardening, the tap root of a root trainer plant resume growth in a
few days and grow in to air through the drainage hole at the bottom of the
container. On contact with the air, the
tap root will undergo a temporary arrest in growth thus preventing any deformation inside the
container. This natural air pruning of tap root will lead to a stress to the
plant and the plant will respond naturally to the stress by producing a large
number of lateral roots in to the well aerated potting medium. The vertical
ridges provided in the container wall direct these roots downwards and thus
prevent their circular growth within the container (Fig. 6). On reaching the
drainage hole at the bottom of the container, these lateral roots will also be
subjected to air pruning leading to further enhancement of stress, like a
vicious circle. As a result, the root system of a hardened root trainer plant
will consist of a central tap root and a large number of lateral roots with
proper orientation as shown in the figure (Fig. 7) Air pruned roots are in a
stage similar to starvation and hence they
present quick and vigorous growth on transplanting to the soil. Because
of this advantage of air pruned roots, there were several attempts (in other
crops) to induce natural air pruning in polybag plants also (Geera et al. 1998).
A budded stump pulled out from the nursery has an average of 20 to 30
lateral roots (Fig. 8). All these lateral roots are pruned out before it is
planted in polybag/root trainer (Fig. 9). Normally only one third to one fourth
of these lateral roots were noticed to regenerate in polybags, while the others
will remain dormant (Soman and Saraswathyamma 2002). The inhibitory effect of
the poorly aerated top soil used to fill polybag was reported to be responsible
for this poor regeneration of lateral roots (Khedkhar and Subramanian, 1995).
In contrast, the root trainers are filled with a well aerated potting medium
and hence, in spite of the limitation of space, the number of lateral roots
produced was noticed to be significantly higher in root trainers compared to
polybag plants (Table 1). Those lateral roots still remaining dormant in root
trainers are stimulated to grow by providing an artificial stress during the
process of hardening. Growth and performance of an advanced planting material
is directly correlated with the number and development of lateral roots and
hence this enforced regeneration of lateral roots is the most important
advantage of the root trainer planting technique.
Transplanting
Pits are taken to provide a favourable condition for the establishment
and growth of transplanted young plants. So, as in the case of polybag
planting, root trainer plants are also transplanted to pits of standard size of
75 cm x 75 cm x 75 cm, and refilling is completed sufficiently in advance to
provide sufficient time to settle the soil. The plant is separated from the
container just before transplanting to the pit. If the plant is pulled out in
an up right position from the container the root system may break causing
severe damage to the plant. Therefore, the plant is held up side down along with
the container and the brim of the container is gently tapped against a hard
surface (Fig. 10) like the tool used for planting operation so that the root
plug come out of the container easily without any damage to the roots. For field planting root trainer plants, there
is no need of reopening the refilled pit as being practiced for field planting
of polybag plants. Here, it is a much
simple procedure; a planting hole is made in the centre of the refilled pit by
pressing an empty container to the depth required and the root plug is inserted
in to this hole. The plant base is made firm by pressing soil from the sides.
Root trainer plants exhibited 100% establishment success on transplanting to
the field. Air pruned roots were noticed to resume growth in the very next day
after transplanting to the field and this quick and vigorous growth of roots is
mainly responsible for the complete establishment success obtained in root
trainer planting technique.
While transplanting, the bud union should remain above the soil surface,
facing towards the North-Eastern direction as in the case of poly bag planting. Field planting has to be
done during favourable season. Plant base may be mulched with dry leaves and
shade with coconut fronds are recommended if severe drought is experienced
immediately after the transplanting.
Generation of advanced planting materials without any serious defect is
very important for a perennial crop like rubber. The World Bank has suggested
that advanced planting materials of tree crops with coiled tap root should
primarily be rejected for field planting (Josia and Jones 1992). But this is
not practically possible in the case of polybag planting technique of rubber because
tap root will invariably coil in polybags if the plant is retained above the
single whorl stage (most probably coiling will be initiated in the single whorl
stage itself). In the root trainer technique, on the other hand, the natural
air pruning of tap root completely prevents its coiling. The quick growth and
increased vigour characteristic of air pruned roots compensate for the loss of
roots cut and removed during the hardening process. A well established tap root
system will improve wind fastness of the tree and the quantum of loss due to
wind damage will be reduced significantly in areas exposed to heavy wind.
Similarly, it is expected that root trainer plants will perform well in drought
prone locations owing to the profuse development of roots consequent to the
hardening process.
Anchorage is the major function of tap root, other functions like
absorption of water, minerals etc. being attributed to lateral roots. So,
future growth and productivity of an advanced planting material is positively
correlated to the number of lateral roots, its vigour, orientation etc. In root
trainer nursery lateral root production is enhanced by providing an artificial
stress during the hardening process and hence a hardened root trainer plant was
found to possess lateral roots much higher in number than polybag plants (Table
1). The vertical ridges in the container wall ensure proper orientation of
lateral roots and the natural air pruning enhances its vigour of growth on
transplanting to the field. Naturally, root trainer plants are expected to
present better growth after transplanting than polybag plants and this has
proved to be true in all the ongoing field experiments with root trainer
plants. (Table. 2). At Churulacode, Kanyakumari District of Tamil Nadu, the
root trainer plants have attained tappable girth at 5 ½ years of growth after
transplanting to the field (Table. 2) while the polybag plants required six
more months to attain tappable girth. The root trainer plants also exhibited
better uniformity in growth than polybag plants.
Root trainer planting technique was standardized to overcome the defects
of polybag plants. In addition to overcoming the drawbacks, root trainer
planting technique was found to be highly cost effective also. Cost of budded
stump is the same for both the planting technique. The cost towards the root
trainer and the carrier is estimated as Rs. 20.00 per unit. The root trainers
and carriers could be reused for a minimum period of fifteen years and hence
the annual depreciation could roughly be worked out to Rs. 2.00 per unit. This
expense is more or less equal to the price of a polybag.
Availability of good top
soil is a major constraint in producing quality polybag plants. There are several reports, which point out
that it takes several hundreds of years to form one inch of top soil in nature and hence top soil is considered as a
priceless commodity. A root trainer requires only 220 to 400 g of coir pith w
as against 8-10 kg of top soil to fill a polybag. So, even if coir pith is
transported from a distant location the cost/unit towards the coir pith will
always be less than the cost of top soil required to fill polybag.
The remaining cost of production of an advanced planting material is the
labour charges. Due to the light weight and compact size of root trainers the
labour required for nursery practices like filling, trenching, stacking,
irrigation and fertilizer application are much less compared to that for
polybag nursery. Coir pith is devoid of any weed seeds and hence the cost of
weeding could be saved in root trainer nursery. Fertilizers, pesticides,
fungicides etc. could also be utilized more effectively than polybag nursery.
Root trainer plants occupy relatively less space in the nursery and hence the
establishment costs like lease rent, fencing, shading etc. could also be saved
significantly. So, based on the experience for the last several years, it could
clearly be stated that the cost of production of advanced planting materials in
root trainers is significantly less compared to that of polybag plants.
The advantages which could be derived during the process of
transportation, field distribution and transplanting to the pit are the most
attractive economic aspect of root trainer planting technique. Due to its
compact size, root trainer plants could be accommodated in vehicles up to
3-times the number compared to polybag plants. Field distribution of root
trainer plants is very simple (Fig. 11). Root trainer plants could be
transplanted to the pit so conveniently and effortlessly that even an unskilled
worker could attain planting turnover several times higher than polybag
planting. The simple method of field planting enables small holders and
marginal farmers to perform their planting operations by themselves without
depending on skilled workers. An estimate made at the Rubber Research Institute
of India in the Kanyakumari district at Paraliar has revealed that the cost
required towards transportation, distribution and field planting of root trainer
plants are approximately one third the cost compared to polybag planting (Table
3).
Taking in to consideration the various advantages, the root trainer
planting technique is being practiced in many western countries since
1979. However, availability of a good potting medium is very important
for the successful implementation of root trainer planting technique. The non
availability of a good potting medium (top soil could never be considered as a
good potting medium) was the main reason for the obsolete polybag planting
technique still continuing in our country. The identification of cured coir
pith as a good potting medium and the availability of this renewable source of
potting medium all over the traditional rubber belt are the factors which
helped successful standardization of this modern planting technique for rubber.
Usage of shredded bark and other alternative mediums like sugarcane waste, rice
husk etc. has to be explored in regions where coir pith is not available.
Summary
The various advantages of root
trainer planting technique could be summarized as follows,
- Air pruned tap root without any deformity grows deep in to the soil which enhances anchorage and wind fastness of the tree.
- Large number of lateral roots ensures good growth and uniformity of plants on transplanting to the field.
- Quick and vigorous growth of air pruned roots help to attain 100% establishment success on transplanting to the field. The sponge-like property of coir pith to absorb and retain water is helpful to safeguard stress due to unexpected delay in rain immediately after field planting,
- Cost of production of advanced planting materials could be saved significantly compared to polybag plants,
- The cost required for transportation, distribution and field planting etc. could be reduced to one third compared to polybag planting. Being less labour intensive, root trainer planting technique provide a solution, to certain extend, to the ever increasing shortage of skilled workers experienced in rubber plantation industry,
- At present coir pith has no great commercial use and is considered as a menace polluting the environment. Root trainer planting technique provides an excellent opportunity for utilization of this industrial waste.
- Root trainer planting technique is more environment friendly, because the reusable root trainers provide a solution to the environmental and health hazards poised by polybags.
Selection of the right planting material is a very important step in
planting a long duration crop like rubber. Unfortunately most of the high
yielding clones were found to exhibit high incidence of TPD also, pointing
towards a possible hindrance to enhance productivity by genetic improvement
beyond a particular level. Under the above circumstances attempt to increase
productivity by improving morphological and physiological qualities of advanced
planting materials is very important and root trainer planting technique is a
step forward in this direction. In addition, rubber cultivation is being extended
to marginal and non-traditional areas confronted with various agro climatic
constraints limiting plant growth and productivity. Hence, it is very important
to develop technologies capable of withstanding stress situations like extreme
atmospheric temperature, prolonged drought, high velocity winds, high
altitudes, depleted soils etc. In this context also root trainer technology has
specific advantages especially for locations with drought and high velocity
wind. It is strongly believed that root trainer planting technique will attain
quick popularity when the immense potentialities of this modern, cost effective
and labour friendly planting technique are realized by the planters.
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