Rubber Cultivation in India: Para, Ceara, India and Russian Rubber Plant

The following points highlight the four main types of rubber cultivation in India. The types are: 1. Para Rubber 2. Ceara Rubber 3. India Rubber 4. Russian Rubber Plant.

Type # 1. Para Rubber:

Para rubber is a tall trees, 25-35 mtr.; stem smooth, straight, un-branched up to a considerable height and then forming a leafy canopy; bark greyish with copious milky latex. Leaves are trifoliolate, alternate or sub opposite, at the end of the branchlets, long petioled; leaflets glabrous, elliptic-lanceolate, acuminate, entire, 10-15 cm. long; petiole 7—10 cm. long, glandular at apex.

Flowers small sweet-scented, unisexual, in large, terminal, panicled cymes. Calyx 5-toothed or lobed. Corolla absent. Disc of 5 free or united glands. Stamens 5-10, filaments united to form a column; anthers sessile on the column.

Ovary superior, 3-celled, with one ovule in each cell; stigma sub sessile 2-lobed. Fruit a capsule, dehiscing into 3 one seeded cocci; seeds ellipsoid, 3-4 cm. long, mottled brown and shinning. Hevea brasiliensis is indigenous to Brazil, Venezuela, Peru, Equator and Colum­bia. It is cultivated in India, Ceylon, Burma, Malay, Sumatra, Java, Borneo, Sarawak, Siam, Indo-china and in Equatorial Africa.

In India rubber plantations were first started in Kerala in 1905 from seeds obtained from Ceylon. Ceylon was however the first country in Asia to start cultivating Hevea brasiliensis from seedlings sent from Royal Botanic Garden, Kew in 1876.

The latex of H. brasiliensis is obtained by tapping the bark of the trunk. The over­flowing latex is collected in a plastic or enamel cup containing a small amount of pre­servative viz. Ammonia or Sodium sulphite or Formaldehyde to prevent coagulation.

As the latex stops flowing the cups are emptied into buckets which are carried to the factory. The liquid is strained first through a course sieve to remove the dirt and other impurities. It is then diluted and strained for second time through a fine sieve. The latex is an aqueous serum with a colloidal suspension of rubber particles.

A warm, humid and equable climate is suitable for growing H. brasiliensis. It thrives well in tropical countries lying between latitudes 15°N and 10°S with a temperature ranging from 74°F and 95°F. A rainfall of 1750 mm. to 2500 mm. well distributed throughout the year is ideal for its healthy growth.

Prolonged rainfall or prolonged drought are unfavourable while moderate showers alternating with sunny weather are much needed.

Deep well-drained loamy soil is best for H. brasiliensis. The pH value should range from 3.8 to 8.0. In alkaline soil the growth is stunted. To start a rubber plantation a forest area is cleared of trees and undergrowth’s and these are left there for some-time. . The tree trunks and the. branches are then removed and the leaves that fall on the soil are allowed to rot.

Arrangement is made for good drainage and terraces are prepared according to the sloping of the land. Square type of pits are dug in lines, 2/3 mtr. deep and of similar width. Pits are filled with surface soil and organic manure.

Seedlings raised in the nursery or clones are transplanted in the pits during monsoon 200 per acre or more. Later the plants are thinned out and about 150 are left in a field of one acre. Seeds are sown in seed beds in the nursery in winter and germinate in 1-3 weeks-time. Seedlings attain a height of one mtr. or more in 6 months’ time when they are ready for transplanting. In trees raised from seeds the yield of latex varies.

In some the flow of latex is high while in others it is much less. So that in a plantation it is desirable to have all high yielding trees. So instead of transplanting seedlings, trans­planting of budded clones are practiced. Such clones are prepared in the nurseries.

Buds taken from high yielding trees are grafted near the base of vigorously growing seedlings about one year old. After a period of one month or a little more the budded stocks are stumped 15-20 cm. above the grafted bud. In another fortnight the budded stumps are ready for trans­planting. After transplanting all other branches excepting the shoot developing from the grafted bud are pruned off.

Suitable cover crops are grown very close to check soil erosion and surface run off. For this purpose Pueraria phaseoloides Bth, Centrosoma pubescens Bth, species of Crotalaria, Indigofera, Desmodium, etc. are generally used. These enrich the soil also.

Sulphate of Ammonia and other nitrogenous fertilizers are used for manuring and this is important when cultivated lands are converted into rubber plantations. For grown up trees in a plantation, potash, phosphate and other fertilizers are used. Small quantity of magnesium is often added.

The rubber trees are susceptible to fruit-rot disease and- die-back disease. The former is controlled by spraying Bordeaux mixture and other by cutting off the affected portions and burning them.

Black thread disease appear in the tapping cuts and this can be prevented by painting that portion with a 5% solution of Brunolium, Agriosol, Solignum or Jodelite. White ants often cause great damage to the trees. These are rubbed off and the tree trunks are painted with tar or kerosene.

Tapping is done on the base of the trunk up to a height of 11 mtr. from the ground. Cuts are made by removing a thin shaving of bark by special tapping knives. Usually the cut extends half way around the trunk but it may completely encircle it, i.e. half spiral system or full spiral system.

It may also be a V-cut system or herring bone-cut system. The cut is made at 30-35° to the horizontal from upper to lower end of the cut and a vertical cut is made to conduct the latex to a cup placed below. In V-cut system two slanting incisions are made and at the base of their junction a cup is placed where the latex is collected.

In herring bone system a vertical cut is made in the bark with 4-6 diagonal cuts on either sides. The cuts extend from one fourth to one half of the circumference of the trunk. A cup is placed bellow the vertical cut to receive the latex. The latex is collected through a small spout fixed into the bark.

Tapping is done early in the morning when the flow of latex is vigorous. The flow diminishes with the rise of temperature and ceases in about 3 hours. The latex is then transferred into large pails or buckets. Tapping is done every alternate day. The yield increases with the repeated scrapings which is stopped before any injury is done to the cambial tissues.

New tapping’s are done one below the other till it reaches almost the ground level on one side of the tree in a period of 5—6 years. After that tapping is done .on the other side of the tree trunk and continued for another period of 5-6 years. Tapping commences when the tree is 7-8 years old.

Increase of flow of latex is effected by treating the bark below the tapping cut with hormones. Seedling trees respond better to such hormone treatment than the bud- grafts. Poor yielding trees are thus converted to high yielding ones.

Fresh latex is susceptible to enzymic and bacterial action leading to acid forma­tion and coagulation. Preservatives and bactericide are added to the latex at the time of collection to inhibit acid development. Ammonia (mainly) formaldehyde, Sodium hydroxide, soap and bactericides are used as preservatives.

Usually a small quantity of ammoniated water is placed in the collection cup to prevent coagulation. Addition of 3 parts of 25% Ammonia solution to 100 parts of latex ensures the stabilisation of the latter for six months.

Stabilized fresh latex free from sludge containing 30-40% of solids is called “Normal latex”. By evaporation, creaming or centrifugation it is concentrated to give’ a product with higher solid contents. Concentration by eletro-decantation is popularly practiced.

The latex is a colloidal suspension of rubber particles in an aqueous serum. Rubber content is richer in hard bark than in the soft bark. Other constituents in the latex are proteins, resins, sugar and glycosoids, tannins, alkaloids and mineral salts.

Raw rubber is obtained from the latex. There are two types of raw rubber, viz. smoked sheet rubber and crepe rubber. To obtain the former type the latex is diluted with water and strained through a sieve to remove the impurities.

This is them coa­gulated by adding Acetic acid or Formic acid. After adding the acid the latex is poured into aluminium pans or tanks and allowed to stand overnight. The rubber coagulates and floats on the surface as spongy slabs.

As the slabs become firm these are taken out and washed in clean water. Washed slabs are pressed between smooth rollers to squeeze out the water and flatten them to a thickness of 3 mm. The sheets are passed through marking rolls to impart a ribbed pattern.

The ribbed sheets are dried on racks or poles in shade for a few hours and then smoked in smoking rooms to make them immune to the attack of moulds. The dried sheets are translucent, amber coloured and elastic. These are then packed for the market.

For crepe rubber the diluted and cleaned latex is mixed with Sodium bi-sulphite and acid. The coagulated substance is cut into long pieces, squeezed, sheared and mas­ticated through a series of differently geared corrugated rollers.

It is then rolled into sheets with rough or corrugated rollers. It is finally rolled into sheets and dried by hanging on racks in well-ventilated drying rooms. Heat is often applied to hasten drying. The sheets are then packed in bales for the market.

In India about 70,000 acres of land are under rubber (H. brasiliensis) plantation. All plantations are located in the south, 91% being in Kerala, 7% in Tamil Nadu and 2% in Karnataka. Annual production is about 27,000 tons and is insufficient to meet the internal requirements of this country.

Rubber is obtained from the latex of several species of plants the most important of which is Hevea brasiliensis (H.B.K.) M. Arg. and the rubber obtained from this tree is known as Para rubber.

This tree is indigenous to Brazil but is cultivated in many tropical countries including India and forms the chief source of commercial rubber. Other rubber yielding plants are:—Manihot glaziovi M. Arg. Ficus elastica Roxb. and Taraxacum Koksaghyz Rodin.

Type # 2. Ceara Rubber:

Ceara Rubber is also is a native of Brazil. It is a small tree not exceeding 12 mtr in height, with a thick bark peeling off in horizontal strips. Leaves are long petioled, palmipartite. The tree is suitable for tapping when 5-years old. Continuous tapping is injurious and kills the tree in a few years-time. The yield of latex as well as the quality is poor in comparison to that of H. brasiliensis.

Ficus Elastica Roxb. (Moraceae)

Type # 3. India Rubber:

Indian rubber is a large tree with prop roots. Leaves are thick and glossy, 12-30 cm. long. Flowers minute, densely arranged in a hypanthodium. The hypanthodia occur in pairs in axils of fallen leaves. The stem and the main branches as well as the thicker aerial roots are tapped for the latex. The latex coagulates readily.

A part coagulates in the cut portion of the trunk while the rest flows down and is collected on mats where it coagulates. The coagulum from cut portion of the tree is pulled out and collected from the mats. The coagulum is then dried, cleaned and pressed into cubes.

The latex is acidic, slightly so when fresh but the acidity increases on keeping. The resin content in the latex is high and the rubber hardens on aging. It is inferior to para-or ceara—rubber. The tree is indigenous to India and is common from Nepal tarai to Assam and extends to Burma.

Type # 4. Russian Rubber Plant:

Russian rubber plants are small herbaceous plant growing as a weed in temperate countries. It is cultivated in Russia.

The leaves are basal, lyrate or pinnatifid. Capitulum terminates a hollow scape. Flowers all ligulate, yellow. The involucral bracts have prominent horn-like appendages.

The latex is obtained from the roots and the rubber is of good quality.