University of Horticultural Sciences, BagalkotKittur Rani Channamma College of Horticulture,Arabhavi Harvesting & Processing of Rubber
TappingHarvesting in rubber is known as tapping.Tapping is the periodical removal of thin slices ofbark to extract rubber latex.It is the process of controlled wounding with theshaving of bark removed. The latex vessels arefound in the inner layer of soft bast of the bark.The latex vessels are concentrated in in the softbast arranged in a series of concentric rings ofinter connecting vessels.Tapping is done by skilled men.
While tapping, the cambium should not bedamaged as otherwise callus formation will takeplace causing swellings. The rubber trees attain tappable stage in aboutseven years. The best season for tapping is March orSeptember depending upon girth of the tree. The latex vessels in the bark flow at an angle of 320to the right and therefore a cut at higher level fromthe left to right has to be carried to facilitateopening of a large number of latex vessels.Tapping is done in the early morning, late tappingwill cause reduction in the flow of latex.
Tapping Systems & IntensitySl.No Tapping Sytems Intensity Remarks 1 s2d2- Half spiral, tapping Recommended for budded alternate days for 6 months 100 % plants. and rest for 3 months. 2 s2 d3- Half spiral, tapping at Recommended for clonal plants. every three day for 6 months 67 % and rest for 3 months. 3 s2 d1 – Half spiral daily Followed by small growers but it tapping. 200 % favours brown blast incidence and causes early deterioration of trees.
In South India, rubber trees shed their leavesduring December- January & immediately againthey put forth the new leaves and flowering.During this period the trees are given rest sincethe yield of the rubber will be poor if tapped.The yield of the rubber steeply increases year byyear and the peak is reached at 14-18 years afterplanting.
Then it slowly declines . After 40 years it maynot be economical to maintain the trees.The latex yield will vary with the clone, age oftrees, fertility of soil, climatic conditions andskill of the tapper.
Types of Tapping1. Puncture tapping Puncture tapping or micro tapping is basically an incision method of tapping. Micro tapping is done with a small needle on a vertical band of stimulated bark. The length of the strip is usually limited to 60 cm and the number of punctures made may be 4 or 5.
2. Slaughter tapping Intensive tapping prior to felling of the old trees is called slaughter tapping. It is often done at higher levels sometimes even on branches with the help of ladders and not on the usual renewed bark levels. As the objective of slaughter tapping is to extract as much as latex as possible from the available bark, no consideration is given to the technique, intensity or standard of tapping.
Rain guarding By fixing a polythene rain guard to the trunk of the tree above the tapping panel, tapping can be carried out during rainy season also Growth regulators like 2,4 dichloro phenoxy acetic acid and 2,4,5 tri-chloro phenoxy acetic acid are applied through vegetables oils these are applied in a broad band round the trunk under the tapping cut of the rubber tree many proprietory products like stimulex, flow more, ready rub containing the above growth regulators are available in the market as rubber stimulant
Generally used anti-coagulants• Ammonia, Sodium sulphate & Fomalin.• Ammonia 0.7% is the most popular latex preservative.
Yield of Rubber• In South India, the annual yield of rubber is about 375 kg/ha from seedlings where as budded plantations yield about 900-1000 kg /ha
Processing of Rubber• The latex that flows out from the rubber trees on tapping is channeled into a container, generally coconut shell cups then is transferred to clean buckets, two to three hours after tapping.• The latex which gets dried up on tapping panel (tree lace) and the collection cups shell scrap also form a part of the crop and are collected by the tapper in baskets just prior to tapping.
• The latex split including over flown on the ground (earth scrap), when gets dried up, is also collected once in a month. Normally 10-20 % of the total crop constitute the tree lace, shell scrap and earth scrap.
Rubber can be processed and marketed as1. Preserved latex concentrates.2. Dried sheet rubber.3. Dry crepe rubber
Preserved latex concentrates• The latex is collected in the storage tank, from there it is brought to a centrifuge machine, rotating at 1400 rpm. Due to centrifugal action, liquid portion comes out.• The upper layer and the concentrated latex, is collected and brought to bulking tank and mixed with chemical and packed in drums. 60% rubber is present in it.
• Skim latex is taken to another tank then sulphuric acid is added which gets coagulated & it is milled to get skim crepe. It is of poor quality while the concentrated latex fetches very higher price.
Dried sheet rubber• Anti-coagulants (solutions of ammonia, Formalin or sodium sulphite are added to the cups to prevent the coagulation of latex before it reaches the factory.• The latex so collected is then bulcked and then strained to remove the impurities. It is then diluted to a standard consistency of 12-15% rubber.• Special hydrometers like mrtrolac, latex meter are employed to measure the percentage of rubber.
• After dilution, the latex is strained through a 60 mesh screen for the second time.• Then it is poured into the special coagulating tanks or aluminium pans which is divided into many compartments by thin aluminium sheets and acetic acid or formic acid is used for coagulation.• Slow coagulation produces a soft rubber which is easy to work on the rollers.• The acid is to be added quickly and mixed thoroughly with the latex. Froth formed is removed to avoid formation of bubbles on the surface of rubber sheets.
• After coagulatuion, rubber sheets are repeatedly washed several times with changes of water & passed through hand or power operated rollers. In the roller excess water & dissolved impurities are pressed & squeezed out• The surface of the rollers may be either smooth, or grooved or zig zag or straight or diamond pattern, its impression is normally left on the surface of the sheets when they come out of the press• These sheets are hung in shade for 2 or 3 hrs, for dripping in a dust free place
• They are taken to smoke houses for thorough drying. Smoking of rubber sheet is done to dry the sheets properly• To avoid formation of blisters. In the smoke house, the sheets are smoked at a low temperature of 48-500 C with fairly high humidity during the first day subsequently during second to fourth day the temperature being 680 C with low RH• They are taken out, graded & packed. Such products are known as smoked sheets or dry ribbed sheet rubber
Various grades of rubber sheets are• RMA IX, RMA-1, RMA-2, RMA-3, RMA-4, RMA-5.• High grade rubber sheets are clear, free from blisters, translucent & of a golden brown colour & fetch a better price.
Dry crepe rubber• When coagulum from latex or any form of field coagulum after necessary preliminary treatments is passed through a set of creeping machines to get crinkly, lace like rubber called crepe rubber after drying.• Various grades of crepe rubbers are• EPC Super 1X, EPC 1X, EPC 2X & EPC 3X.