On Rubber: The Rubber cultivation in Indi....same idea can be shifted to Africa........ Many plant species produce natural rubber. Considerations of quality and economics, however, limit the source of natural rubber to one species, namely Hevea brasiliensis. 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. 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 and winters from December to February in India. Refoliation is quick and copious flowering follows. 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 – 7 years of immature phase and 25 years of productive phase. Propagation of Rubber In India, Hevea seeds normally ripen during July-September when the seeds are collected and seedlings raised. All earlier plantations were raised from unselected seeds. The yield potential of these having been low, the production of those plantations was poor. Selection work on Hevea with a view to improving the planting materials and the introduction of vegetative propagation by budding led, in course of time, to the establishment of numerous valuable clones. Clonal Seeds Seeds of clones are termed clonal seeds. There are different kinds of clonal seeds – monoclonal, polyclonal, legitimate and illegitimate. Monoclonal seeds of clone Tjir 1 which gave rise to seedlings superior to seedlings from ordinary, unselected seeds were once encouraged for planting extensively in our country. Evolution of newer, improved planting materials then progressively replaced Tjir 1 clonal seedlings. Hybrid polyclonal seeds collected from approved polyclonal seed gardens are the only seed material recommended for planting now. For production of good quality polyclonal seeds, gardens have been established in Kanyakumari district. Polyclonal garden seeds in the name Prang Besar Isolated Garden (PBIG) seeds from Malaysia used to find limited market in India until a few decades ago. Polyclonal seedlings: Seeds collected from clonal stands are known as clonal seeds.In olden days monoclonal seeds of single mother clones such as Tjir 1, not contaminated by crossing with seedling rubber or undesirable male parent clones,had been extensively used as improved planting materials. Now only clonal seeds of polyclonal origin which can be expected to possess significant hybrid vigour are accepted. Ployclonal seeds of good clones are planted in such seed gardens mixe as per specific designs. For prevention of pollen contamination from rubber trees of neighbouring area, an isolation belt of 100 meters width is provided all around. Polyclonal seeds give rise to seedling of good vigour and growth. Compared to buddings, they are easier to establish and maintain. The trunk of seedling is much larger than those of budded trees. Owing to the inherent genetic variability, they are relatively less suceptible to wind damange and disease. However, the general yield levels are far lower than selected modern clones. The high tree to tree variability in growth and yield makes it necessary to adopt thorough selection of seedling for planting based on initial viour, high initial planting density in the main field and subsequent judicious thinning out of weakilings and poor yielders in a phased manner. Still, the trees exhibit proneness to tapping panel dryness. The average annual yield is 1200 to 1300 kg/ha/yr. 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 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 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. Nurseries Nurseries are required for raising seedlings, budded stumps and budwood. As far as possible 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. 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, watering, weeding etc. Planting distances should vary according to the type of planting materials to be raised in the nursery. The ideal spacing for seedlings is 30 cm X 30 cm. For budwood nurseries, the plants may be at distances of 60 X 90 cm or 60 X 120 cm or 90 X 90 cm 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 obviously 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. Budding The principle involved in 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 buddings 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 utilised. Depending on the part of the stock where budding is carried out, buddings are classified into four types: base budding, crown budding, over budding and high budding. Base budding is carried out at the base of the stock plant and includes brown budding, green budding and young budding. Brown Budding Brown budding is generally carried out by grafting brown coloured buds taken from budwood of about one years growth onto stock plants of 10 months or more growth. Vigorously growing healthy stocks having a girth of 7.5 cm at the collar region are ideal for budding. Stocks should be budded when the bark peels off very easily. Peeling is usually good when the top whorl of leaves is well developed, but before further extension growth commences. Test peeling of a small patch of bark above 15 cm from the base is the sure method to assess the peeling quality of the bark. Since all stock plants may not attain this stage at the same time, more than one round of budding may be necessary to cover all the stocks. Brown buds are usually obtained from brown budwood produced by budded plants raised in budwood nurseries. Buds found in the axils of fallen leaves are generally utilised for budding. Budwood should be collected when the top whorl of leaves have fully expanded but not hardened to ensure proper peeling of the bark and high budding success. Test peeling may be carried out before harvesting the budwood. Collection of budwood should be done with sufficient care so as to avoid bruising. As far as possible, budwood should be collected in the morning or evening, and should preferably be utilized for budding as soon as collected. If budding is delayed, special measures should be adopted for preventing moisture loss. Budwood is harvested as per the requirement and cut into pieces of convenient length, usually 1 m. Good quality budwood will have around 20 healthy, well formed buds per metre length. Weak and poorly formed buds should not be used. While handling budwood of different clones, proper labelling has to be done for identification. Budding is usually carried out with a specially designed knife having two blades, called budding knife. However, an ordinary pen-knife with a blade of 7 to 8 cm length could also be used. The first step in the preparation of the stock plant for budding is thorough cleaning of the basal 15 cm to remove dirt, soil, etc. Cleaning can be done with cotton waste or rags. Then two parallel vertical cuts starting from about 2.5 cm above the collar are made. The length of these cuts should be a little more than 5 cm and 1.5 cm apart. Then a horizontal cut joining the bottom ends of the vertical cuts is also made. All the three cuts should be made deep enough to reach the wood. After making these cuts the latex is allowed to completely ooze out for a few minutes through the cuts. During this time the budder can mark a few more stocks in a similar manner. When the latex flow ceases, it is wiped off from the surface. The flap of bark separated by the three cuts is then gently lifted with the aid of the knife and peeled upwards. Alternatively, the upper ends of the vertical cuts may be connected by the horizontal cut and the flap peeled downwards. The practice of removing the flap completely is also adopted. The exposed region is called the budding panel. The bud patch used for brown budding should have a length of about 5 cm and a width of about 1.5 cm. For preparing the bud patch, two parallel vertical cuts having a length of 5 cm are made on the two sides of a bud, 1.5 cm apart. Then two horizontal cuts are made connecting the lower and upper ends of these cuts. A little time is allowed for the latex to ooze out. During this time, incisions are made around neighbouring buds of the same budwood. When the oozing of latex stops, it is wiped off and the bud patch marked out by the four cuts is stripped off by gently pushing to one side. After removing the bud patch from the budwood, the inner side is examined carefully for the presence of the core of the bud, which appears as a slight projection. If it is not present, the bud patch should be discarded. The bud patch should be handled with utmost care so as to avoid any damage to the cambium. It should always be held at the edges without touching the cambium. Foreign matter like water, soil and sweat should not be allowed to fall on the cambium. Similarly exposing the cambium to strong sunlight or dry wind can result in its drying. All these can cause damage to the cambium. Damage to the cambium of the budding panel also should be avoided. The four edges of the bud patch are then slightly trimmed. The bud patch is then gently placed in the budding panel after lifting the flap. It should be placed in such a way that the bud is above the leaf scar and its inner side is in contact with the budding panel. Exposure of too much area of the budding panel around the bud patch is unfavourable for budding success. At the same time the edges of the bud patch and budding panel should not touch each other. After placing the bud patch in the budding panel in the above manner, the flap, if retained, is placed back over it and is then bandaged using polythene strips of 45 cm length, 2.5 cm width and 250 gauge thickness. Bandaging should commence at the bottom and move upwards in a close spiral. During the first few turnings of the bandage, the lower end of the flap should be kept gently pressed over the bud patch to prevent it from slipping. Bandaging should be tightened to keep the cambium tissues of the budding panel and the bud patch in intimate contact with each other. The end of the tape is finally kept intact with a knot. In the field and along borders of nurseries it may be necessary to shade the bud patch against strong sunlight. This can conveniently be done by tying a rubber leaf over the bud patch. If the budding is successful, the cambium of the stock plant and that of the bud patch unite and the bud patch establishes as a part of the stock. The process requires 15 to 20 days and the plant is left undisturbed for 20 days after which the bandage is removed. The flap, if it had been retained, is cut a little above the upper end of the bud patch and removed. Freshness of the bud patch indicates initial success of the budding. The final success is ascertained in a similar manner after another 10 days. Green Budding Both the stock plant and budwood used for green budding are very young. Seedlings which are five to seven months old are used as stock. Buds are collected from six to eight weeks old budwood, also known as bud shoots or bud sticks. Buds found above the scale leaves of the shoots alone are used for budding. These buds are green in colour and hence the name green budding. Young, vigorous seedlings raised in nursery or in polythene bags are used as stock plants for green budding. Plants having a girth of about 2.5 cm at the base, with brown bark up to a height of about 15 cm, can be used for this purpose. The stock plants require about four to five months to attain this size. By proper care, this period could be further reduced. Green budwood is obtained from budwood plants (source bushes) grown in nurseries for this purpose. They are collected when six to eight weeks old, when they have a length of 30 to 60 cm with a whorl of leaves at the top. The bud shoots are harvested by cutting at the base with a sharp knife. For proper peeling of the bud patch, harvesting should be done when the leaves are copper brown to dark green in colour. After harvesting, the leafy portion of the shoot is cut off. The non-leafy portion shows two to five scale leaves with axillary buds which are utilised for budding. After cleaning the basal portion of the stock, two vertical incisions, a little more than 5 cm long and 1 cm apart are made starting from a point about 2.5 cm above the collar region. The lower ends of these cuts are joined by a horizontal cut and a few minutes allowed for the cessation of latex flow. The flap is then cut off leaving a short tongue of about 1.5 cm at the top. The stock is now ready to receive the bud patch. The bud patch can be stripped from the bud shoot in the same way as in the case of brown budding. However, other methods can also be employed for this purpose. In one such method, a 6 cm long bud patch shaped like a pointed tower is marked out. Then the top 1 cm is separated from the bud shoot and holding on to this portion (by touching the inner and outer sides), the whole bud patch is gently stripped off. The top 1 cm of the bud patch with damaged cambium is pruned off. In a third method the bud patch along with a thin slice of wood is first taken from the bud shoot. This is the bud slip. The two sides of the bud slip are trimmed to the required width. The bud patch is then gently separated from the wood by pulling them apart. While doing so care should be taken to see that the bud patch does not bent. Only the slice of wood is bend. After separation, the lower and upper ends of the bud patch are also trimmed. When finally prepared, the bud patch should have a length of approximately 5 cm and a width of 1 cm, so that it fits snugly into the budding panel. The upper end of the bud patch prepared in the above manner is gently inserted under the `tongue’ and placed in the budding panel. Then the bud patch is secured firmly by bandaging with a transparent polythene strip as in the case of brown budding. This strip should be about 25 cm long and 2 cm wide. Transparent tape is insisted upon as it allows light to fall on the green bud patch which in turn enhances budding success. For the same reason, no shading is given. Buds are examined three weeks after the budding by observing through the bandage or after removing the bandage. Retention of the green colour is the indication of budding success. Final observation on budding success is done after 10 more days. If the observations are made through the bandage, after the second observation, the bandage is removed. The plant is now ready for cutting back. Budding can be carried out at any time of the year. However, too dry or very wet weather is unsuitable. Generally more success is obtained during rainy season than in summer. Experiments have shown that in India the period from April to October is generally suited for brown budding. The success rate of green budding is more during summer months also. However, heavy rainfall is not suited for budding. For best results, budding should be carried out either in the early morning hours or in the evenings. Both brown budding and green budding have certain advantages and disadvantages. Advantages of Green Budding over Brown Budding i. It utilizes the growth of the stock more efficiently, i.e. when green budded plants are cut back, only a small amount of stock growth is lost, ii. Green budding is simpler and faster than brown budding and hence more number of plants can be budded reducing the labour cost per budding, iii. It gives higher percentage of success during summer than brown budding, iv. Opening of the budding and cutting back can be done simultaneously, thus saving labour cost, v. Yield of green buds from a unit area of nursery is two to three times that of brown buds, vi. Since the polythene strip used for green budding is smaller, cost incurred for this material is reduced, vii. After cutting back green buds develop earlier than brown buds, viii. Green budding is more suitable for crown budding. Major Defects of Green Budding Technique i. Green bud shoots cannot be retained in the nursery for long after they become mature enough for harvesting, ii. After harvesting, green sticks cannot be kept for long periods, unlike in the case of brown budwood iii. Scion of green budding is less vigorous than that of brown budding and hence it requires very careful attention during the early period of growth, especially in the field. Young Budding This is a kind of green budding carried out on very young plants less than two months old. Stocks are raised in small bags of lay flat size 33 x 15 cm. The plants are given intensive nursing such as foliar application of fertilisers and fungicides twice weekly and soil application of NPKMg mixture weekly. When seven to eight weeks old, they are green budded. Four weeks after budding, plants are cut back leaving a snag of 20 to 25 cm length. Buds on the snag are nicked or the shoots coming from then pruned off promptly. When the scion develops two or three whorls of leaves, the plants are transplanted to the field. This technique has got certain advantages over the normal green budding technique. By adopting this technique bag plants could be produced within seven months after the planting of germinated seeds in the bags, which is usually done in August/September. In our country, the time required for this is around nine months in the case of normal green budding. Since small bags are used for the production of plants transportation is easier. The cost of production is also slightly less compared to the normal method. Since the stock plants required for young budding are raised by sowing seeds directly in the bag, these plants have a better developed root system than the plants raised from green budded stumps. A well-developed root system prevents breaking of soil core and ensures faster and easier establishment of plants after transfer to the field. However, under the climatic conditions existing in our country this method does not have much practical application because by the time the bag plants produced from young buddings are ready (February - March) the climate becomes unfavourable for field planting. Hence planting has to be delayed up to the onset of monsoon (June). Bag plants produced from green buddings also becomes ready by this time. Crown Budding Replacing the undesirable crown of a high yielding clone with a desirable crown is of practical significance. In many of the modern clones, though the trunk possesses a capacity for high yield, the crown shows many undesirable characters like susceptibility to wind and diseases. An undesirable crown can be replaced by a desirable one through crown budding. The tree produced by crown budding is a three-part-tree comprising the root system of the stock plant, trunk of one clone and the crown of another clone. Thus the desirable characters of the trunk of one clone and crown of another clone are combined. Crown budding is ideally carried out when the scion of the budded plant has attained a height of 2.4 to 3 m. One to two years are usually required for the plants to attain such a growth. The height of the plant is more important than the age. Crown budding may be commenced when 50 to 60 per cent of the plants in the field are buddable. Budding is carried out at a height of 210 to 240 cm on the inter-whorl region below the top whorl of leaves. It should be done only when the top flush of leaves are fully expanded and hardened. Stem tissue should be green or dark green at the time of budding. This ensures maximum budding success. Too tender or too mature stem tissues adversely affect budding success. If the topmost flush of leaves are not mature enough, budding could be done below the second whorl of leaves provided all other conditions are satisfied. Plants having height up to 4.5 m can also be used for crown budding. In the case of such overgrown plants having green tissue at a height higher than the prescribed, the height of budding has to be raised correspondingly so as to carry it out below the top whorl. For crown budding, the green budding technique is followed. Since the budding has to be done at a higher level, a self-supporting ladder should be used. On no account should the plant be bent for budding or any other operations. If the budding is a failure, rebudding is done on the opposite side of the stem, 5 cm above or below the first budding. Successfully budded plants are cut back leaving a snag of about 5 cm. Treating the cut ends of the stem with some wound dressing compound is desirable. After cutting back, usually many trunk shoots arise. All of them should be pruned regularly at fortnightly intervals with a knife having a long handle. This should be continued until the crown bud sprouts and the crown shoot grows to a length of about 2.5 cm. After that, two or three trunk shoots arising about 15 to 45 cm below the crown shoot are allowed to grow. These shoots should be spaced apart and be on different sides of the stem as far as possible. They should never be allowed to become more dominant than the crown shoot, as this may suppress the growth of the latter. For this, if necessary, the top portion of the trunk shoots may be pruned. About nine months after cutting back, when the crown-trunk union is firmly established, the trunk shoots are pruned. Necessary precautionary measures have to be taken for the protection of the crown shoot especially from wind damage and perching of birds. The crown shoot later on fully establishes itself and in due course develops to be the crown of the three-part tree. If the crown shoot is lost for some reason before the pruning of the trunk shoots, the most vigorous among them is again crown budded, if possible, or allowed to develop as the crown. Over Budding Budwood plants are sometimes budded at higher levels for converting an existing budwood nursery of a clone to another clone without replanting. This is termed as over budding. The method adopted is to carry out budding at the basal portion of the brown budwood before harvesting it. The budwood is harvested after the new bud is successfully attached to the plant, by cutting above the budded portion. Since the budding is carried out on a well-established plant, the scion emerging from the new bud grows vigorously producing more budwood compared to a newly established budwood plant. Thus it is a quick and economic method for converting budwood nursery of one clone to that of another. Tissue Culture Propagation of rubber is possible through tissue culture also. Tissue culture or micro propagation is the technique of producing plants from small (micro) pieces of plant tissues. Studies on tissue culture of rubber plants were started in 1966. Different parts of the plant such as embryo, anther, shoot tip and integument can be used for tissue culture. Rubber Research Institute of India has developed a technique for the production of tissue culture plants from shoot tips as well as somatic embryogenesis of different tissues. Rubber plants were developed by the somatic embryogenesis of anther tissue, integumental tissue, immature inflorecence etc. Attempts are being made for the tissue culture of other plant parts like leaf, floral buds, ovules and micro spores. Key steps in tissue culture of hevea include collection of the explant, sterilization, inoculation of the explant in a nutrient media supplemented with growth hormones and sucrose. The cultures were kept under optimum light and temperature conditions for the required period. Plants were formed in about eight months. They were then transferred to small polybags and kept in a green house for hardening. Even for the same clone the culture conditions vary with the physiological stage of the explant, seasons, part of the plant used etc. Because of these variations separate protocols have to be developed for each clone. This is a laborious and time-consuming process. However, procedures have been perfected for the propagation of several important clones by optimising these parameters. As in the case of most other tree crops, multiplication rate in tissue culture is very low for rubber. Further in the post-laboratory stages mortality is very high. However, after overcoming all these hurdles the RRII has successfully developed a large number of plants through various methods of tissue culture. These plants have been established in the field . Test tapping carried out on certain clones over their bud-grafted control and they are under different stages of evaluation. Preparation and Packing of Propagation Materials The propagation materials handled by rubber growers are ungerminated seeds, germinated seeds, seedling stumps, brown budwood, green bud shoot, brown budded stumps, green budded stumps, polybag plants and 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. 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. Ungerminated Seeds Fresh and healthy seeds collected from the field can be kept under shade without much loss of viability for about seven days. Storing fresh seeds in water at ambient temperature increases their water content, which in turn prolongs the viability. By packing seeds loosely in well-aerated containers with powdered charcoal having 20 per cent moisture, 70 per cent viability can be retained up to 30 days. Storage of seeds at 4oC in sealed polythene bags is also considered to be a reliable method for retaining viability up to four months. Immediately after collection, seeds are generally packed in powdered charcoal of 20 per cent moisture for transportation. Containers usually used are wooden boxes, double gunny bags, bags lined with polythene or polythene bags. For transporting over very long distance, seeds may be packed tightly in layers in aerated cases with damp sawdust-charcoal powder mixture, at least 2 cm thick between two layers of seeds. Germinated Seeds Germinated seeds are collected from germination beds when the radicle just comes out of the seed. If the root is allowed to elongate it may get damaged while packing and transporting. To prevent this, germination beds are inspected every day and germinated seeds are picked up. Brown Budwood After harvesting, the brown budwood is cut into pieces of one metre length with a pruning saw for the convenience of handling. Immature top portion, which may be green or partially brown, is discarded. For use on the same day and transporting over short distance brown budwood is kept wrapped in wet sacking. For longer storage and transporting, their cut ends are sealed with melted wax and each piece covered with banana sheath, wet sacking, coconut fibre, or grass leaves. They are then tied into bundles of convenient size. By this method, viability could be retained up to three days. For storing up to 14 days and carrying over very long distances each piece is first wrapped with perforated polythene and then packed in boxes with wet sawdust or coconut fibre. Green Bud Shoots After collection of the shoots, their leaf bearing top portion is cut off. The leafless lower part having the scale leaves are used for taking buds. Since green bud shoots are tender it is better to use them for budding immediately after harvesting. Usually shoots harvested in the morning are used on the same day, preferably by noon. In the seedling nursery they are carried in trays or buckets containing water or kept rolled in wet sack or cloth without touching each other and always kept in shade. If packed with wet, aged saw dust in alternating layers after sealing the cut ends with wax, storage is possible up to six days. Seedling Stumps Seedling prepared to a convenient size by pruning the stem and roots are called seedling stumps. Healthy and vigorous one year old seedlings are generally used for this. The seedlings should have a minimum girth of about 7.5 cm at the base and brown colour up to a height of 45 cm or more. For stumping, at first, the seedlings are cut back at some point between 45 and 60 cm, where the brown colour ends. Pruning is always done with a slanting cut, preferably above a whorl of buds. While cutting back green or partially brown stem should not be retained on the plant. Transpiration can take place through such regions and the resulting loss of water may lead to the drying of the stumps after planting. The plants are left in the nursery for 7 to 10 days. During this period a few buds below the cut end become activated and swell. At this stage the decapitated plants are pulled out without causing much damage to the roots and bark of the stem. The taproot is pruned to the maximum possible length, but not more than 60 cm and not less than 45 cm. The minimum of 45 cm is insisted for the sake of better establishment and the maximum of 60 cm is fixed for the convenience of handling. Lateral roots are pruned to a length of 10 to 15 cm. Plants infected by diseases or having defective roots are discarded. If more than one taproot is present the most vigorous one alone should be retained and all others pruned off at the base. After preparing the seedling stumps by proper pruning of roots and stem, the cut end of the stem is immediately sealed by dipping in molten paraffin wax. For transporting over short distances they are tied into bundles and then covered with a layer of grass or leaves. In this manner they can be stored up to three days. If transporting over large distances and storing for days together are required, it is better to avoid stumping the seedlings days before pulling out. Pruning of shoot and roots may be carried out after pulling out. The stumps in such cases are packed in boxes along with wet saw dust in alternate layers. Brown Budded Stumps Brown budded plant prepared for planting by pruning the stem and roots is known as brown budded stump. The ideal way to prepare a brown budded stump is to cut the stem of the plant at a height of about 7.5 cm above the upper end of the bud patch. The cut should have a downward slant of around 45o from the side of the bud to the opposite side. The plants are then pulled out and the taproot pruned to a length of 45-60 cm and the laterals to a length of 10-15 cm. While gripping the stem for pulling out the plant, special care should be taken not to exert any pressure on the bud patch. Otherwise there are chances for the bud to get damaged. In case it is found difficult to pull out the plant after cutting back the plant can be pulled out before cutting back and then pruned. If the budded stumps are intended for planting in polybags the taproot should be pruned to a length about 15 cm less than the height of the soil core. Rejection of defective plants, pruning of multiple taproots etc. are similar to those of seedling stumps. Brown budded stumps are hardy and hence a proper method of packing retains the viability for a longer time. The cut ends of the stem are first sealed with melted wax. The bud patch is protected by covering with a small piece of banana sheath or folded rubber leaf. For overnight storing, they are kept erect in water as in the case of seedling stumps. For retaining their viability up to three days and carrying over short distances they are tied into bundles and each bundle covered with banana sheath, grass or leaves. At the time of planting the protective covering of the bud patch is removed. For long distance transport of budded stumps involving preservation over a few weeks, advance cutting back of budded plants before pulling out should be avoided. The freshly cut back and pruned budded stumps should have their cut ends sealed by molten wax and the whole stump given a light fungicide treatment. They are then packed in boxes with wet sterilized sawdust. Green Budded Stumps Green budded stumps are prepared from green budded plants in almost the same way as that of brown budded stumps. The major difference is that if cutting back is done before pulling out it should be done seven days before pulling out as green buds require lesser time for activation. Green budded stumps being comparatively tender and smaller with less reserve food stored in them, it is always preferable to plant them immediately after preparation. Packing methods adopted for green budded stumps are basically the same as that adopted for brown budded stumps. Protection to the bud patch can also be provided by retaining the polythene strip used for bandaging the bud patch at the time of budding. Standing in water enables preservation overnight. Additional steps like sealing of the cut end of root, tying into bundles and covering the bundles with grass etc. gives protection for two days. If packed in boxes with wet saw dust these could be safely stored up to six days and transported over long distances. In the case of both types of budded stumps described above the budded plant should be pulled out without much delay after budding. If retained in the nursery for a long time the dormancy of the buds will increase and consequently their sprouting after planting may be delayed. Polybag Plants While transporting polybag plants utmost care should be given to prevent any damage to the soil core. If the soil core is damaged roots may break and consequently the plant will be deprived of all the advantages of bag planting. Transporting over a short distance is done by carrying them on the head or shoulder. Vehicles like lorry, truck, tractor, etc. are used for transporting over long distances. While transporting by vehicles, the bags are stacked on the platform tightly to reduce their swaying and shaking to the minimum. Providing shade for protection from hot sun is also desirable. The bag should always be kept in a vertical position while loading, unloading and transporting. Carrying them in inclined or horizontal position may cause breaking of soil core. Care should also be taken to avoid tearing of the bags as it also can increase the chances for breaking of the soil core. Stumped Buddings Stumped buddings are mainly of two types, mini stumps and maxi stumps. To prepare ministumps the scion is cut back when it develops brown colour up to a height of 60 cm from the bud union. Pruning is done at the point where brown colour ends preferably below a whorl of buds. The cut end is treated with any wound dressing material to prevent dehydration. Stem is then white washed with hydrated lime to avoid sun-scorching. Ten days are given for the activation of buds. Then the plants are pulled out and the roots pruned as in the case of budded stumps. If pulling out is found to be difficult due to the deep taproot it can be made easy by removing the soil at one side of the taproot up to a depth of 45 to 60 cm. A crowbar is inserted through this opening and the taproot is severed at the desired depth. This is called tailing. For preparing maxi stumps cutting back of the scion is carried out when brown colour is formed up to a height of 240 cm. First step in the extraction of the plant is the tailing which is done five weeks before pulling out. Early tailing reduces the transplanting shock and enhances the development of new roots from the cut end after transplanting. After tailing soil removed for this purpose is placed back. Pollarding of the stem is done 10 days before pulling out at a height of 240 cm. where brown colour ends. As in the case of mini stumps pruning of stem is done below a whorl of buds. Wound dressing, white washing, pulling out and pruning of lateral roots are also undertaken as done for ministumps. Packing and transporting of mini stumps are similar to that of seedling stumps. Maxi stumps are not usually made into bundles due to their large size. They are packed head to tail on lorries or trailers, using grass or leaves as packing medium to prevent bruising and drying. Root trainer plants Root trainer plants Root trainers generally used have a length of 26 cm with a capacity of 600 cc. The specific features like tapering shape, vertical ridges in the container wall, drainage hole at the bottom are all incorporated with the purpose of properly training the structural development of roots and hence the container is termed as root trainer. Cured coir pith mixed with the appropriate quantities of single phosphate, neem cake, bone meal, fungicides and pesticides is used as the potting medium. After planting budded stumps, preferably greed budded stumps, the root trainers are stacked in carriers made of iron rod or bamboo splints. Initially the base of the container is covered with top soil and the roots growing out of the soil put beneath the containers is removed, roots are pruned and the plants along with the containers are kept suspended in air for hardening for a minimum of eight weeks. During the hardening process the tap root resumes growth in a few days and undergoes natural air pruning near the hole at the bottom and thus prevent its coiling inside the container. This stress induces emergence of large number of lateral roots into the well aerated potting medium. The vertical ridges of the container wall direct these roots downwards and thus prevent its circular growth. These lateral roots also undergo air pruning and as a result a hardended root trainer plant will have a root system consisting of central tap root and large number of lateral roots well oriented without any deformity. The root plug is separated from the container just before transplanting to the field. The root trainer plant is kept up right down and the brim of the container is tapped against a hard surface so that root plug comes out of the container without causing any damage to the roots. A planting hole is made in the refilled pit by pressing the empty container itself and the root plug is inserted into it. The soil is pressed slightly from the sides and all other cultural practices are adopted as in the case of polybag plants. Exporting of Propagation Materials Propagation materials to be sent abroad should be packed in strong containers using enough packing medium to avoid damage during transit. Container, packing medium and propagation materials should be free from diseases and pests. Methods like fumigation, dusting, spraying, dipping, etc. with fungicides and pesticides can be adopted for this depending on the suitability. Phyto-sanitary certificate issued by the competent authority of the dispatching country should accompany each parcel of the propagation material. When carried by air the materials should be kept in the warm pressurized compartments of the aircraft to avoid low temperature and low pressure. Clones Click here to view the details of each clone The planting materials approved by the Rubber Board are classified in to three categories I, II and III. Category I comprises of materials approved for large scale planting. However, it is strongly recommended that these may be used to cover only 50% of the total area of any estate or small holding. Category II comprises clones, which have shown their merit in performance in India over long term or medium term periods. It is recommended that three or more of these clones be used to plant up to 50 per cent of the total area of any estate or small holding. Category III planting materials are divided into (a), (b), (c) and (d). Materials under division (a) are those which have held out promise of good performance in small-scale trials, and over short term in some large scale trials in India or abroad. Hence these are approved only for experimental planting. Those under division (b) are old selections having promising localised performance or having desirable secondary attributes. In regions where these clones are showing very good performance, no restriction in planting is insisted. Modern clones with moderate scale performance are included in division (c). Other experimental clones of promising yield and/or desirable secondary characters with limited data are included in division (d). Selections from any of these are recommended for very small scale planting not exceeding 15 per cent of the total area. Agro-climatic Requirements Humid tropical climate prevails in the rubber-growing tract. Average annual rainfall in the tract varies from about 2000-4500 mm. The southern parts of the traditional tract enjoy southwest and northeast monsoons almost equally while the northern areas receive mostly the southwest monsoon. From south to north the drought period extends from two to five months in a year and the distribution of rainfall becomes more uneven. However, variation in temperature and humidity in the rubber tract is not so marked as that of the rainfall. The temperature remains very warm and humidity very high throughout the year. Sub Topics Climatic Conditions for Optimum Growth of Rubber Tree 1. Rainfall of 2000 to 3000 mm evenly distributed without any marked dry season and with 125 to 150 rainy days per annum 2. Maximum temperature of about 29oC to 34oC and minimum of about 20oC or more with a monthly mean of 25 to 28oC 3. High atmospheric humidity of the order of 80% 4. Bright sunshine amounting to about 2000 h per annum at the rate of 6 h per day through all the months 5. Absence of strong winds Only a few regions in India meet all these requirements. Fortunately rubber can be grown successfully under moderately deviating conditions too. Soil Type Soil in the rubber tract is generally highly weathered and consists mostly of laterite, lateritic types. Sedimentary types and nonlateritic 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. 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. 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, stumped buddings and soil core plants. 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.
Posted on: Sat, 01 Feb 2014 13:54:42 +0000
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