Rubber tree
Many plant species produce natural rubber. Considerations of
quality and economics, however, limit the source of natural rubber to one
species, namely Hevea brasiliensis.
It is a native of the Amazon basin and introduced from there to countries in the tropical belts of Asia and Africa during late 19th century. It can be termed as the most far reaching and successful of introductions in plant history resulting in plantations over 9.3 million hectares, 95 per cent of it across the globe in Asia.
It is a native of the Amazon basin and introduced from there to countries in the tropical belts of Asia and Africa during late 19th century. It can be termed as the most far reaching and successful of introductions in plant history resulting in plantations over 9.3 million hectares, 95 per cent of it across the globe in Asia.
Hevea brasiliensis, also known as the Para rubber tree after
the Brazilian port of Para, is a quick growing, fairly sturdy, perennial tree
of a height of 25 to 30 metres. It has a straight trunk and thick, somewhat
soft, light brownish gray bark. The young plant shows characteristic
growth pattern of alternating period of rapid elongation and consolidated
development. The leaves are trifoliate with long stalks. The tree is deciduous
in habit and winters from December to February in India. Refoliation is quick
and copious flowering follows. Flowers are small but appearing in large
clusters. Fruits are three lobed, each holding three seeds, quite like castor
seeds in appearance but much larger in size. The seeds are oil bearing.
The rubber tree may live for a hundred years or even more. But its
economic life period in plantations, on general considerations is, only around
32 years – 7 years of immature phase and 25 years of productive phase.
Commercial cultivation of rubber in India was started in 1902.
Rubber tapping is the process by which the latex is collected from a rubber tree.
An incision is made in the tree's bark, which cuts
through the latex vessels, from which the product then flows. Timing of the
incision must be planned within the planting cycle to optimise the latex yield.
Tapping Systems
Response to different
tapping systems varies from clone to clone. In general budded trees are
tapped on half spiral alternate daily (S/2 d2) system and seedlings on half
spiral third daily (S/2 d3) system. Alternate daily tapping is the
recommended frequency for medium yielding clones (RRIM 600, GT 1, PB 28/59
etc). For high yielding clones like RRII 105, PB 260, PB 217 etc, low
frequency tapping systems with stimulation may be practiced. However, low
frequency tapping can be adopted for medium yielding clones also. (See
description on low frequency tapping)
Tapping Notations
Tapping notations are sets of symbols and numbers describing mode of tapping and its frequency. An internationally recognised system is in existence. This consists of three parts to indicate
1. Tapping method
2. Panel position and type 3. Stimulation followed for cut tapping and puncture tapping
The notations for
tapping method include notations for type of cut, length of tapping cut,
direction, frequency etc.
Some Examples
S
:One full spiral cut
V :One full V-cut S/2 :One-half spiral cut S/4 :One-fourth spiral cut 2 X S/4 :Two one-fourth spiral cuts on the same tree S/2 U :One-half spiral cut tapped upwards 2 x S/2 DU :Two half spiral cuts, one tapped upward and the other tapped downward d1 :Daily tapping d2 :Alternate daily tapping d3 :Third daily d2 6d/7 :Alternate daily, six days in tapping followed by one day rest.
Standard system is
taken as S/2 d2 and intensity is taken as 100%.
To calculate relative intensity, multiply four times the ratio of the length of tapping cut (expressed in fraction) and the tapping interval with hundred. Example: S/2 d3 : 4 X 1/2 X 1/3 X 100 = 66.6% |
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Panel Notation
Panel is the area of bark in which tapping cut is located. Panel notation indicates the panel position and renewal succession of the panel. This helps to describe tapping. Common Panel Notations |
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First, second, third
and fourth high panels of the virgin bark above the standard height of
opening are indicated by HO-1, HO-2, HO-3 and HO-4 respectively. Renewed bark
is usually not tapped in high panels.
Low Frequency Tapping
(LFT)
Survival of natural
rubber industry is being threatened by low and fluctuating prices, escalating
cost of production and scarcity of skilled tappers. Tapper wages constitute a
major component of cost of production. In view of the situation, low
frequency tapping systems, which judiciously combine stimulation, is favoured
in most countries. From the d2 system, the initial shift was towards d3, with
a subsequent shift to d4 system. Weekly tapping (d6) has also been attempted.
Trees under low
frequency tapping (d3, d4 & d6) have to be stimulated from opening
onwards for achieving maximum sustainable yield. Number of stimulations to be
given vary with clone, age of the tree and frequency. In high yielding clones
like RRII 105 and PB 217 under third daily (d3) tapping frequency, 15 to 30%
sustainable yield increase can be achieved by three annual stimulations
(April/May, September and November). In the case of medium yielding clones
like RRIM 600 and GT1, four annual stimulations (April/May, August, October
and December) are recommended under third daily (d3) tapping frequency.
Comparable yield to
that under d3 frequency of tapping with stimulation can be achieved from d4
frequency of tapping. Six annual stimulations (April/May, June, August,
September, November and December) are recommended for clone RRII 105 and five
(April/May, June, August, October and December) for clone PB 217. In the case
of clone GT 1, seven annual stimulations (March, April, June, August October,
December and January) have to be given. For weekly tapping of clone RRII 105,
fortnightly stimulation is to be given in the initial two years after
opening, and monthly in the subsequent years. Trees which have undergone
higher frequencies of tapping for the initial two or more years, when converted
to weekly tapping, yield stimulation at monthly interval may be
followed. Stimulation recommended is 2.5% Ethephon on the panel (width
of 1.5cm on the recently tapped young tissue) in all the above cases. The
scheduled stimulation for the month of April may be postponed to the month
of May or June under d3 and d4 frequency, if soil moisture is
deficient.
Low Frequency Tapping (LFT) with stimulation can be practiced from the first year of tapping. Trees under high frequencies of tapping can also be converted to LFT. Conversion to d3, d4 or d6 frequency will result in substantial saving in cost of production. However, when such conversions are done there will be a temporary yield depression for 3-4 months. To minimize such loss, connversion may be done only during low yielding months (Feb-April).Under d4 frequency, one panel can be tapped for at least 8 years and under d6 frequency the duration can be increased further to 10 years. Combined with CUT, economic life can be increased to at least 50 years from the current 30 years provided sufficient stand exists. When tapping is done by the grower himself, weekly tapping with rain guard would be most appropriate.
Benefit to tappers
from low frequency tapping is also substantial through increased over
poundage. This will lead to substantial increase in the standard of living of
tappers.Since the success of LFT depends on regular tapping throughout the
year under the opted frequency, timely fixing of good quality rainguarding
and an additional rainguard fixed during August/September is essential in the
traditional region including the agroclimatic conditions in Kulasekharam in
Tamil Nadu. Whenever tapping is not done due to absence of the tapper or
holiday, the field/block scheduled for such day/s should be tapped on the
next day. If such blocks are tapped on the 8th or l2th day, there will be
severe temporary reduction in yield. Delayed/second collection has to be done
for around six months. If DRC falls below 30%, stimulation may be suspended,
till it is improved.
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* Fortnightly
stimulation in the initial two years.
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NB:
Controlled Upward
Tapping
Controlled upward
capping (CUT) can be practiced for longer exploitation of the virgin bark
above the basal panel. In CUT instead of using ladder, a long handled
modified gouge knife is used for upward tapping from the ground. Bark
consumption is minimised as far as possible. Higher yield can be obtained for
many years as there is neither any bark-island effect nor any injury to
cambium. CUT can be adopted in plantations under the following
situations
1. Low yield from
the renewed bark
2. Renewed bark is unsuitable for tapping because of outgrowths, diseases, panel dryness etc. 3. For prolonged crop harvesting of high panels or for prolonging economic life after the completion of BI-2 panel (D Panel) 4. For simultaneous tapping of both basal and high panels (intensive tapping) for one or two years while in B I-1 and B I-2 stage.
In the first two
situations CUT can be adopted after completion of tapping in virgin bark. For
CUT, the tapping cut is opened on the virgin bark just above the renewed bark
of the base panel. The tapping cut can be 1/4 spiral and its slope 450.
Length of the tapping cut would depend on the duration for which controlled
upward tapping is to be done. Normally with alternate daily tapping, one
panel can be tapped for two years (24 months). Thus with 1/3 spiral cut
tapping can be done for six years. The duration can be increased with 1/4
spiral cut. There are many practical problems associated with 1/2 spiral
cut and hence it is better to tap quarter or one-third spiral cuts.
Experience has shown that it is better to open 1/4 spiral cuts irrespective
of girth. Tapping is done on the upper cut with maximum control on bark
consumption (not to exceed 3 cm/month) and maintenance of the angle of cut at
450. Injury to cambium should be avoided. For CUT, modified long handled
gouge knife must be used. With this, it is easier to minimise bark
consumption and to reduce injury to cambium. Another advantage of the knife
is reduction in spillage. Length of the handle is 120 cm for tapping upto 40
cm height of the high panel and 180 cm for tapping beyond that height. While
tapping, left hand guides the knife and active movements are made by the
right hand. The left hand should not be raised above the shoulder and right
hand above the elbow.
In CUT, monthly bark
consumption should be restricted to 3cm. If necessary, the support cut may be
cleaned at times to prevent spill over. Since it is difficult to rainguard
the CUT panel, it is advised to rest the panel during rainy season. The best
system is periodic panel change i.e. no tapping on upper panel during rainy
season (approximately 5-6 months) during which the base panels can be tapped
with rainguard. Thus with tapping rest on high panel during rainy season, one
high panel can be tapped for 24 months (3-4 years), leading to increased
duration of crop harvesting on high panel. On completion of one panel, next
panel may be opened on the right side of the existing panel (while facing the
tree).
Tapping cut in the
high panel can be stimulated using 5% ethephon following lace application
method. For quarter spiral cuts stimulation can be done during
wintering also. Under third daily (d3) tapping of ¼ spiral in the high
panel, monthly stimulation is enough for high yielding clones and stimulation
at intervals of once in three weeks is necessary for medium yielding
clones. For d2 tapping of S/4 cut in medium yielding clone, monthly
stimulation can be done. However, stimulation during extreme drought
may be avoided. When very high yield is obtained from CUT panel,
stimulation need not be done.
When tapping is done
only in the high panel, for 1/3 or 1/4 spiral cuts, task size can be the same
as that for a half spiral cut in the base panel. When simultaneous tapping of
high and base panels are done, it is better to tap quarter or one third
spiral cut in the high panel. The task can be 50%.Special training of 3-5
days is required to use the modified gouge knife and to tap without raising
the left hand above the shoulder level and right hand above chest height.The
tapping frequency for CUT is the same as that of base panel i.e. d3 frequency
for high yielding clones and d2 frequency for medium and low yielding clones.
The best system for CUT in Kerala is periodic panel changing, with base panel
tapping with rainguard during rainy season and CUT on high panel during
non-rainy season including summer months.
Around 5O% increase in yield over long term can be achieved by adopting CUT.
Intensive Tapping
Intensive tapping is generally done on old rubber trees for a few years prior to their removal. The methods of intensive tapping depend on the condition of the trees, previous tapping systems, availability of the bark and the period available for crop harvesting before felling. The methods employed are increased tapping frequency, extension of tapping cut, opening of double cuts and use of yield stimulants. While opening two cuts at the same time, the cut should be sufficiently apart at least by 45 cm to avoid the interference of drainage area between the cuts.
High Level Tapping
When tapping of renewed bark on basal panels becomes uneconomic, new cuts are opened at higher levels, 180 cm from bud union or even higher. The tapper uses a small ladder to reach the cut. Since ladder tapping is more strenuous and time-consuming, usually reduced tapping tasks are given (135 trees). |
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