Resin is a solid or highly viscous, non-crystalline organic compound obtained from plants or may be of synthetic origin that is typically convertible into polymers.
Resin tapping involves causing physical injury to the cambium layer and sapwood of the tree and collecting the exuded resin in a metal or plastic pot.
The resin tapping system was started in the fifteenth century in America. In Nepal, it started in 1973. Altogether, 80 species of pine trees have been taped for resin globally.
Some of the Pinus species for resin tapping are-
- Pinus roxburghii (Chir pine)
- Pinus kesiya
- Pinus oocarpa
- Pinus elliottii
- Pinus massoniana
In Nepal, Pinus roxburgii is being tapped for resin.
Methods of Resin Tapping
On the basis of the intensity of tapping,
- Light and continuous tapping
- Heavy tapping
Based on the incision-making technique,
- Bark chipped method
- Rill method
- Borehole method
Light and continuous tapping
This type of resin tapping method is applied in all trees above 0.9 m in girth. Trees between 0.9-1.8 m in girth are tapped in one channel and above 1.8 m girth in two channels for five years.
At the end of five years, a new channel is tapped leaving 10 cm space from old channels in an anticlockwise direction, and so on till tapping has progressed around the tree.
Under this tapping, a tree is always kept under tapping without any period of rest. It gives a sustained and better yield without impairing the health of trees.
This is also known as “tapping to death”, and is common in developed countries. It is applied in trees above 0.6m girth. In this method, the maximum possible quantity of resin is exuded by making many possible channels in 10 cm space.
It is generally initiated five years in advance of the main felling in prospective regeneration
area and two years in advance in areas marked for thinning.
Bark chipped method
Three methods are applied;
Chinese method: A downward pointing v-shaped groove is made each day. The groove should be deep enough to reach the cut to the secondary xylem.
The GRoove should be made at 1.2 m above the ground and subsequent cuts are made below it till it reaches the half-round tree’s circumference. A chemical stimulant is not used.
American method: A horizontal groove is made 20 cm above the ground. A new groove is
made every 15 days till the length of the groove reaches one-third of the tree’s
circumference and height from 2 to 3 cm. A stimulant is used.
French method: Slices of 8 to 10 cm width are made in the trunk every 10-15 days till the height reaches 1.8 m from the ground in two year
In this method, holes of 2.5 cm diameter and 10 cm depth are drilled in the trunk. Many boreholes are made around the tree’s circumference at an interval of one month during resin tapping season. Stimulant is applied inside holes.
The rill method of tapping has been considered more economical than other methods. The process of resin tapping under this method is described below;
- The loose and rough bark over a surface area of about 45cm*30cm, above 15 cm from the ground is removed using a Bark shaver.
- A blaze is marked of 32cmx16cm size on the stem with the help of a blaze frame and marking gauge.
- A long central groove of 4 mm depth and 7-9 mm width is made with the help of a grove cutter drawing the cutting tool from above downwards.
- Rills of 2mm depth are made at 45 degrees on both sides of the groove with a knife.
- The rills should be parallel to each other.
- Once 1st rill is made, the 2nd rill has to be made on the other side after 3 days. The average width of the bark left between consecutive rills is 5 mm.
- The lip of 7 cmx6.5 cm is fixed and inserted into the bark at the bottom of the groove, and a nail is driven into the tree about 2.5 cm below the midpoint of the lip for hanging the collection pot/cone on it. A chemical stimulant is sprayed on the freshly cut rill (Dilute sulphuric acid and Dilute Nitric acid of 1:1 ratio, 20% concentration level)
- In 8 months season (Chaitra- Kartik), 32/32 rills can be made in one season.
- The resin is collected in a collection pot/cone.
- At the end of the tapping season, the nails are pulled out and the lip is removed.
- For installation during the second year of tapping, the position of the blaze is marked above the top of the first year blaze leaving about 4 cm of bark.
- Resin can be collected for 5 years. After 5 years, a new blaze is made leaving a 7.5 cm wide space along the circumference of the tree from the edge of the first blaze
- This method yields about 22% more resin and is applied in Nepal.