Everything you need to learn about para-rubber plant cultivation, processing and growth.
Introduction to Para-Rubber:
The para-rubber plant, which is a native of Brazil, was introduced into tropical Asia in 1876 and is now extensively cultivated in India, Sri Lanka, Malaysia and Indonesia. The plant is also grown in tropical regions of Africa and America. So far as India is concerned, rubber plantations were first started in Kerala in the year 1905. Since then rubber cultivation has been taken up in many other areas.
Although Kerala is the most important rubber- producing state in India with concentration of plantations in Kottayam and Quilon districts, Kanyakumari district in Tamil Nadu is also important in this respect. Rubber is produced in small areas in Coimbatore and Nilgiris in Tamil Nadu, in Coorg in Karnataka and in Andaman Islands.
The para-rubber plant (Hevea brasiliensis (H.B. & K.) Muell.-Arg.) belongs to the family Euphorbiaceae. It is a tall, quick-growing, hardy tree, 18 to 30 metres in height. The trunk is straight and it produces branches 3 to 5 m above the ground level. The branches form a spreading or conical canopy. Leaves alternate, compound and dark green in colour. Flowers are in axillary panicles, small, unisexual and monoecious. Female flowers are larger than male flowers. Fruit is a capsule with 3 seeds with hard testa. Endosperm is oily.
Climate and Soil of Para-Rubber Cultivation:
A fairly well-distributed annual rainfall of 200 cm and a uniformly warm, humid climate with temperature varying from 21°C to 35°C are very suitable for the tree. It can withstand dry spells of short duration, lasting for one or two months, but longer spells are harmful. It does well from the sea-level up to elevations ranging from 450 to 600 m.
The plant thrives best on deep, well-drained loamy soil, the pH of which varies from 4.5 to 6.0.
Cultivation of Para-Rubber Plant:
Plant propagation is done from selected seeds. It is also done vegetatively from buds. As the seeds remain viable for a short period, they should be sown as soon as they are collected. The soil of the nursery is prepared by mixing it with fertilizers. Beds of 30-120 cm width and of convenient length are then prepared for the germinated seeds to be planted in them at a distance of about 30 cm × 30 cm.
Good healthy seedlings are uprooted from the nursery when they attain a diameter of 20 to 25 mm above the collar and transplanted in pits in the field in June-July. Before they are put in the pits, the roots are lightly trimmed. The pits are dug in the field at a distance of about 4.5 m so as to accommodate about 500 plants per hectare initially. Sometimes, instead of seedlings, seeds are sown in the field and, for this purpose, 2 or 3 seeds per pit are used. Afterwards, all the plants in a pit except the most robust one are pulled out.
Propagation may be done vegetatively by bud-grafting, using buds from selected mother clones. Budded stocks are ready for transplantation in about 4 weeks after budding. They are cut 10 to 15 cm above the bud-patch and transplanted in the field. The recommended planting density in the case of budded plants is 420 to 450 plants per hectare. The plants take about seven years after their transplantation in the field to be ready for tapping.
A leguminous cover crop, such as Pueraria phaseoloidies, is commonly raised between the rows of the trees with the object of preventing soil erosion. The other advantages are its ability to maintain low temperature of soil and conserve soil moisture; besides, it adds humus and nitrogen to the soil. Further, a good cover crop can also smother weeds.
In order to ensure maximum production, regular manuring of the trees with balanced fertilizer mixtures is necessary. This should be done from the time of planting to the age of economic production. The dose of fertilizer mixture varies with the age of the plant. During the first year, a single dose of 225 g of 10: 10: 4: 1.5 NPK Mg mixtures may be applied to each plant.
The dosage is increased to 900 g and 1,100 g during the second and the third years respectively and the application is done each year in two split doses. From the fourth year till the time of tapping, 900 g of the mixture per plant is to be applied in two split doses in April-May and September-October. For trees under tapping, 900 g of 10: 10: 10 NPK mixture is applied to a tree in April-May.
Tapping:
Latex is obtained by tapping from the bark of the tree. Tapping is a process of controlled wounding, which removes thin shavings of the bark and thus induces the flow of latex. Deep cuts are made in the bark extending to half the circumference of the tree and then they slope down to the right.
At the base of the vertical groove, to which the cut leads, a zinc or iron spout is fixed. The latex is then collected in a coconut shell, which is placed below the spout. Tapping should start early in the morning when the flow of latex is high. The flow stops after two or three hours and the latex is collected in buckets and taken to the collection-shed or factory.
While tapping should be deep, proper care should be taken not to cut the cambium. Frequency of tapping is different in bud-grafted plants and seedlings. In the former, it is once in two days and in the latter, it is once in three days.
Tapping can be done almost throughout the year except during monsoon and winter. The number of tapping days in a year varies from 240 to 300. Synthetic hormones are sometimes used to increase the yield of latex. Normally, a tree can be tapped economically for 25 to 30 years.
Processing:
Immediately after the latex reaches the factory, it is weighed and the impurities are removed from it by sieving. The rubber content is then estimated. The latex, which is afterwards standardized by adding water, is allowed to stand and sieving is done again. It is then poured into almuminium trays of standard size or into bigger tanks.
Formic acid or acetic acid of a standard strength is added to the latex so as to coagulate it into a soft mass of whitish colour. This is washed in running water and pressed between smooth rollers to remove the water and convert the mass of rubber into sheets. The sheets are then passed through grooved marking rollers.
The wet sheets are dried partially in shade and then taken to smoke houses for thorough drying for 4 or 5 days, at a temperature of 43° – 60°C, after which the sheets are graded according to quality and packed for despatch to manufacturers. Besides these sheets, pale crepe and sole crepe are also made, for which different processes are used.
Yield:
While the yielding capacity of the older material does not exceed 1,000 kg per hectare per year, that of modern clones ranges from 2,000 to 3,000 kg or even more.
Uses of Para-Rubber:
Rubber is now used in the manufacture of a wide variety of products for the industries, services and also for domestic purposes. Nearly 50,000 different products require rubber for their fabrication, either directly or indirectly. About 75% of the total rubber consumption is accounted for by tyres and tubes of automobiles and cycles. Roughly about 6% of the total world production is utilized in footwear industry and about 4% for wire and cable insulations.
Among other articles, which require rubber for their manufacture, the important ones are rubberised fabrics, foamed rubber in upholstery and mattresses, motor mountings for absorbing vibrations and shocks, washers, transmission and conveyor beltings; hose pipes, gaskets, sports goods, hot-water bags and ice bags, surgeon’s gloves, toys, erasers, etc. Latex threads are used for making elastic fabrics. It is also used in the fabrication of fountain-pen barrels, tobacco-pipes, telephones and combs.
Varieties of Para-Rubber:
Many of the high-yielding clones used in India have been evolved in Malayasia, Indonesia and Sri Lanka. In this connection, mention may be made of PRIM, PB and Glenshiel from Malayasia; Tirandji, Dater and Bodjong from Java; AVROS from Sumatra and Mil, Wagga and Hil from Sri Lanka. Certain Indian clones developed by the Rubber Research Institute of India (RRII), which are superior to foreign clones, are now being distributed for small-scale planting.
Diseases of Para-Rubber:
The common diseases of para rubber are:
(i) Abnormal leaf fall, Black thread, Canker and Pod rot caused by Phytophthora palmivora, which can be controlled by spraying oil-based copper oxychloride at 21.50 kg of copper to 22 litres of oil per hectare and treating the tapping surface with a weak solution of Albolinum.
(ii) Powdery mildew caused by Oidium heveae, which can be controlled by dusting with sulphur at 8 kg per hectare.
(iii) Bird’s eye spot caused by Helminihosporium heaveae, which can be controlled by spraying with 1/2 per cent Bordeaux mixture.
(iv) Die-back caused by Botryodiplodia theobromae, which can be controlled by pruning the diseased parts and by digging out the affected roots and burning them on the spot.
(v) Charcoal rot caused by Ustulina zonata, which can be controlled by cutting down the trees and uprooting the stumps of shade trees, digging a trench around the over-grown trees and cutting all side-roots.
(vi) Brown root disease caused by Fomes noxius, which can be controlled by scraping the affected bark, exposing the roots and drenching them with Aretan or Ceresan and applying Prowex to the treated roots.
(vii) Pink disease caused by Pellicularia salmonicolor, which can be controlled by burning the affected branches and spraying with Bordeaux mixture.
(viii) Dry rot caused by Ustulina deusta, which can be controlled by scraping the diseased portions of the bark and painting it with a fungicide.
(ix) Spearhead drying caused by Diplodia spp., which can be controlled by timely protection of the affected surface by white-washing with lime during the dry season.
Insect Pests of Para-Rubber:
The common insect pests of para-rubber are:
(i) Termites (Cryptotermes dilatatus), which can be controlled by raking 5% Aldrin into the soil around the plants.
(ii) Mango stem-borer (Batocera rufomaculata), which can be controlled by inserting into the holes and tunnels swabs of cotton-wool soaked in petrol or carbon bisulphide or chloroform or 0.13% Dichlorvos or 0.05% Trichorofan and sealing the holes with mud.
(iii) Scale insects (Aspidiotus cyanophylli, Saissetia nigra), which can be controlled by pruning and destroying the affected parts and spraying 0.04% Diazinon, Monocrotophos or Methyl demeton.
(iv) Shot-hole borer (Xyleborus biporus), which can be controlled by spraying 0.1% BHC + 0.1% DDT (W.P.).
(v) Bark-boring caterpillar (Aetherastis circulata), which can be controlled by the same method as in the case of No. (iv) above.