RUBBER CULTIVATION

Many plant species produce natural rubber. Considerations of quality and economics, however, limit the source of natural rubber to one species, namely Hevea brasiliensis.

Introduction

• 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.

Botanical Description

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. Re-foliation is quick and copious flowering follows (pengeluaran bunga yg lebat).

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, i.e. 7 years of immature phase and 25 years of productive phase.

Germination of Seeds

Rubber seeds lose viability very rapidly if left in the field. The seeds are therefore picked up daily during the seed fall season and quickly transported to nurseries for germination and planting.

For germination, raised level beds (tapak semaian) with a 5 cm thick layer of river sand, 90 cm wide and of convenient lengths are used. Partial shade in order to prevent strong sun is necessary.

The seeds are sown in a single layer touching one another and germination beds are kept moist, but not wet, by evenly sprinkling water during morning and evening. The seeds are covered with loosely woven coir matting (sabut) or gunnies.

• Germination starts 6 to 7 days after sowing. Seeds sprouted each day should be picked and planted in nursery beds or in the field as the case may be. Germinated seeds will have young roots emerging first. That is the ideal stage for nursery planting.

• The sproutings are tender and require careful handling. Usually, germinated seeds are carried to nursery beds in buckets half filled with water.

• About 75 percent germination is considered good. Pickings are done for about 21 days after sowing

1. Nurseries

Nurseries are required for raising seedlings, budded stumps and budwood.

Open and level land should be selected for raising nursery. Water should be easily available for irrigation. The soil should be deep, well drained and fertile.

2. Nursery Establishment

• Nurseries are established and maintained for raising various propagation materials for planting. These include seedling stumps, budded stumps and advanced planting materials like polybag plants, etc.

• Mother plants or source bushes for the multiplication of budwood are also grown in nurseries. Raising of plants is easier and cheaper in nurseries than in the main field.

• Moreover, nurseries offer an opportunity for selection of vigorous and uniform plants

The land should be dug to a depth of 75 cm and all stumps, roots, and stones should be removed. Nursery beds should be prepared with 60 to 120 cm width and convenient lengths and with pathways laid in between to facilitate manuring (fertilizing), watering, weeding etc.

Planting distances should vary according to the type of planting materials to be raised in the nursery.

The ideal spacing for (a) seedlings is 30 cm X 30 cm, (b) budwood nurseries, the plants may be at distances of 60 X 90 cm or 60 X 120 cm or 90 X 90 cm

3. Nursery management

• Nursery management aims at the most rapid production of standard healthy planting materials. More intensive care can be exercised in a nursery than in a field. Plants which are unsuitable can be eliminated at an early stage.

• Mainframe operations for nursery include weeding, mulching, irrigation during dry months, manuring and disease and pest control.

Planting materials for establishing rubber plantations are generated in:

–Seedling nurseries,

–budwood nurseries and

–polybag nurseries.

Bud Grafting

• The principle involved in bud grafting (budding) is the replacement of the shoot system of a plant with that of another more desirable plant. In this process, a patch of bark of the seedling plant (stock) is replaced by a patch of bark with a dormant bud (bud patch) taken from the clone to be multiplied. The bud patch gets attached to the stock permanently and becomes a part of it.

The stock is then cut off above the budded portion and the grafted bud develops into a shoot (scion) exhibiting the characters of the plant from which it was taken. The new tree thus formed is a two-part tree, comprising a root system belonging to the stock plant and a shoot system contributed by the donor of the bud.

• Depending on the colour and age of the buds as well as the age of the stock plants used, three types of bud grafting are mainly recognized. These are:

- brown (conventional) budding, - green budding, and - young budding.

• In the first method, older buds having brown colour are used while in the other two, green tender buds are utilized.

Preparation and Packing of Propagation Materials

• The propagation materials handled by rubber growers are (a) ungerminated seeds, (b) germinated seeds, (c) seedling stumps, (d) brown bud wood, (e) green bud shoot, (f) brown budded stumps, (g) green budded stumps, (h) polybag plants and (i) stumped buddings.

• Specific techniques are required for the preparation of these materials.  If not properly prepared, their quality could be reduced, which in turn adversely affects the establishment after planting.

Contd/-

• After preparation, these materials may require storing and/or transportation. During storage and transit they are likely to get damaged by loss of moisture or by breaking, rubbing, bruising, crushing, etc. To avoid these and to give ample protection to these materials, certain specific methods are adopted for packing and transporting.

Soil Type

• Soil in the rubber tract is generally highly weathered and consists mostly of laterite or lateritic types. Sedimentary types and non-lateritic red and alluvial soils are also seen in some non-traditional areas. 

• The laterite and lateritic soils are mostly very porous, well drained, moderately to highly acidic, deficient in available phosphorus and varying in potassium and magnesium content.

• Red soil found in some areas is characterized by reddish to brown colour and fine loamy texture.  This soil is generally acidic and highly deficient in available phosphorus.

Climatic conditions

• The climatic conditions for optimum growth of Rubber tree consist of (a) Rainfall of around 250 cm evenly distributed without any marked dry season and with at least 100 rainy days per annum (b) Temperature range of about 20°C to 34°C with a monthly mean of 25°C to 28°C (c) High atmospheric humidity of around 80% (d) Bright sunshine amounting to about 2000 hours per annum at the rate of 6 hours per day throughout the year and (e) Absence of strong winds.

Soil Depth

• Soil for rubber cultivation should have a minimum depth of one metre without any intervening hardpan or impenetrable layer.

• Water table should also be well below one metre so that at least one metre of soil with good aeration, essential for root penetration is available.

Drainage

• Well-drained soil is essential for optimum growth and yield of rubber plants. 

• In marshy areas, owing to poor physical properties and waterlogged conditions growth of rubber is always found to be very poor.

Field Planting

• The success of planting depends on the prevailing weather conditions, quality of the planting materials used and the care with which the planting operation is done. Continuous wet weather is considered to be ideal for planting rubber.

• The actual method of planting will depend on the materials used for planting. Different types of planting materials used are seeds, seedling stumps, budded stumps and polybag plants.  Of these, the last two are the most common ones.

Intercropping

• During the initial years of a rubber plantation, the land area is not fully occupied by the rubber plants and inter spaces are available in the plantation which receive plenty of sunlight.

• These interspaces can be utilized for growing intercrops, which will help the farmer to generate additional revenue.  Intercrops should be planted at least 1.5 m away from plant bases.  Intercrops should be separately and adequately manured or fertilized.

• The topography of the rubber plantations vary from level lands to gentle, moderate and steep slopes.  The high rainfall in the rubber growing regions and the undulating topography in many situations make the soil vulnerable to erosion hazards.

• Growing of intercrops necessitates soil disturbing tillage operations of various kinds. This will predispose the top soil to erosion losses in steep and undulating lands.

• The growing of intercrops, therefore has to be restricted to level lands and gentle slopes. Even in such lands it should be ensured that leguminous cover crops are established side by side with intercrops or immediately after the intercropping is stopped. The general practice of growing leguminous ground covers has to be strictly followed in plantations of moderate and steep slopes.

Ground Cover Management

• The undulating topography coupled with the high rainfall of the traditional rubber growing region pre-dispose the soil towards erosion.

• In order to conserve soil and improve soil fertility cover crops are grown and maintained. Leguminous ground cover enhances the growth and yield of rubber.

• Advantages of Cover Crops•  Prevent the beating action of rain and effectively

reduces run off •  Increase soil moisture and keep down the

temperature during summer •  Smother weeds •  Add large quantities of organic matter and

improve soil structure • Fix atmospheric nitrogen resulting in improved

soil fertility

Common Leguminous Cover Crops Grown in Rubber Plantations

• Pueraria phaseoloidesThis is a very popular cover crop in rubber plantations. It is a vigorous twiner and creeper and forms a dense thick ground cover when established. It can withstand strong sun and smother weeds.  It is propagated through seeds and cuttings. Seed rate about 3.0 to 4.5 kg per ha. A disadvantage is that it is grazed by cattle unless afforded protection.

• Calopogonium mucunoidesIt is a twine and creeper with tolerance for poor soils. It has a rapid initial growth and dies off during the dry months and is a prolific seeder. Seed rate is 3.0 to 4.5 kg. per ha.

• Centrosema pubescensA perennial climber and creeper that can grow in shade. It grows slowly and is not tolerant to wet conditions. It smothers weeds. Seed rate is 3 -4.5 kg per ha.

Mulching, Shading and Whitewashing

• Mulching or covering the plant basin with dry leaves, cover crop cuttings, grass cuttings, paddy straw etc is a recommended practice in rubber plantations to protect soil in the immediate vicinity of the plants from direct impact of heavy rains and sunlight causing soil degradation.

• Benefits of Mulching* Improvement of water and plant nutrient holding capacity of the soil* Maintenance of the soil around young rubber plants in a cool and moist condition during hot months* Multiplication of microbial population of the soil, ensuring better nutrient availability* Protection of the soil from beating effect of heavy rainfall resulting in soil erosion* Control of weeds around the plant bases

Induction of Branches

• It has been observed that to achieve a high rate of girth increase the rubber plant should produce branches at a height of about 2.5 to 3.0 m from the ground. In high branching trees girth increment has been found to be poor compared to low branching trees.

• Some plants show a tendency for high branching, particularly clones like RRIM 600 and GT 1. In such cases branching has to be induced by encouraging a few lateral buds to develop.

• The branches thus induced should develop in different directions in an equally spaced manner to ensure a well-balanced canopy.

Common Weeds

• Borreria sp. (Button weed), • Chromolaena odorata (Siam weed), • Lantana aculeata  (Lantana), • Mimosa pudica (Touch-me-not), • Clerodendron sp., • Mikania micrantha (Mile-a-minute), • Sida sp., • Imperata cylindrica, • Pennisetum sp. (Napier grass), • Axonopus sp (Carpet grass), • Paspalum sp., Digitaria sp. (Tropical crab grass),

Cynodon dactylon (Bermuda grass) etc.

Tapping and Stimulation

• Latex is obtained from the bark of the rubber tree by tapping. Tapping is a process of controlled wounding during which thin shavings of bark are removed.

• The aim of tapping is to cut open the latex vessels in the case of trees tapped for the first time OR to remove the coagulum which blocks the cut ends of the latex vessels in the case of trees under regular tapping.

Diseases and Pests

• Crops losses resulting from ravages of diseases in rubber plantations are substantial.

• Timely plant protection operations ensure healthy growth and economic production.

• The major diseases and pests of rubber are given below.

Abnormal Leaf Fall

Shoot Rot

Powdery Mildew

Colletotrichum Leaf Disease

Bird's Eye Spot

Leaf Spot

Pink Disease

Patch Canker or Bark Canker

Black Stripe, Black Thread or Black Rot

Dry Rot, Stump Rot Collar Rot or Charcoal Rot

Brown Root Disease

Poria Root Disease

Scale Insect

Mealy Bug Termite (White Ant) Cockchafer Grub Bark Feeding Caterpillar Mites Slug and Snail Rat Porcupines and Wild Pigs Cover Crop Pests Parasitic and Non-Parasitic Maladies

Production

Close to 21 million tons of rubber were produced in 2005 of which around 42% was natural. Since the bulk of the rubber produced is the synthetic variety which is derived from petroleum, the price of even natural rubber is determined to a very large extent by the prevailing global price of crude oil.

• Today Asia is the main source of natural rubber, accounting for around 94% of output in 2005. The three largest producing countries (Indonesia, Malaysia and Thailand) together account for around 72% of all natural rubber production.

• Many high-yielding clones have been developed for commercial planting. These clones yield more than 1,500 Kilogrammes of dry Rubber per hectare (or, over 4 tons per acre), per annum, when grown under ideal conditions