The use of rubber tree (Hevea sp.) budded-stumps
Rubber trees are perennial plants of economic importance that belong to the genus Hevea. Propagation of this tree crop is by vegetative reproduction with clones, resulting in early development and establishment in plantations of genetically superior genotypes, in productivity, quality of latex, resistance to the pest and diseases, among other interesting traits. Bud grafting is the method traditionally used for the production of grafted-seedlings and depending on the physiologic age of the tissue, is either called green or brown grafting. Several types of grafted-seedlings are produced and one of these uses bare roots, commonly practiced by rubber tree growers. Another form, more advanced compared to bare root seedlings, is the use of budded-stumps, usually recommended for reconstitution of stands in areas already established or for replacement of spindly plants. This type of seedling, having a minimum height of 2.50 m of mature brown stem, lends itself to be explored as live fence stakes in pasture areas, with the advantage of an economic and durable alternative, also in support of a positive environmental view. This concept is being implemented in a livestock farm (Comandatuba Farm, Una, Ba, Brazil) and the procedure for the preparation of materials as live stake is presented in the present article.
Location and characteristics of Comandatuba Farm
This farm is located in the municipal district of Una, in the State of Bahia. The prevailing climate is wet without a defined dry season, with annual medium temperature of 23.6° C, annual averages for relative humidity and annual precipitation of 84.6% and 1800 mm, respectively. The type of soil of the property is classified as yellow oxisol, unit Una. This is basically a pasture farm formed predominantly by Bracchiaria humidicola. These pastures were just fertilized twice, to the five and 12 years, with 100 kg/ha of triple phosphate.
Preparation of the budded-stumps
Remains in nurseries seminal material of H. brasiliensis or even abandoned grafted plants in clonal gardens were the source of the seedlings used. The age of this material varied between two and five years and was available in the Djalma Bahia Experimental Station (EDJAB), in Una, Bahia.
The preparation of seedlings involved: 1) opening of a trench along the row of existing seedlings, about six weeks before transplanting; 2) pruning off the taproot at the depth of 60 cm, at the same time as the opening of the trench. This allowed for inducing the process of "hardening" of the tissues, to better-overcome water deficiency at a later stage (Figure 1 and 3). The aerial part of the plants were cut back four weeks after pruning off the taproot (two weeks before transplanting), at a minimum height of approximately 2.40 m with visual brown bark formation, preferably between two rosettes of foliar flushing and in sequence was protected with a fungicide paste. The removal of the aerial part was aimed to break the dormancy of buds and force the flushing as near as possible to the top of the stem (Figure 2 and 4). The stumps were whitewashed immediately after elimination of the aerial part as a preventive measure against the loss of water by transpiration. This solution was prepared by dissolving 1.0 kg of whitewash in five liters of water to which was added 50 ml of a fixative product or 500 g melted ox glue (Figure 3).
The plucking the budded-stumps
The plucking of the budded-stump seedlings was undertaken fifteen days after the preparation previously mentioned. The lateral roots were cut adjacently to the gutter with the aid of a spade and the stumps were plucked by making upward and side movements. After this, the lateral roots were trimmed properly to about 5 cm of length.
Root induction treatment
Due to the high cost and time period required to obtain budded-stumps (at least 18 months old), the trimmed roots were treated with a product to induce the development of new roots and consequently, to improve the index of success. The process involved the immersion of the taproot up to half of its length, in a solution of naphthalene acetic-acid (NAA), at a concentration 2000 ppm, and the thicker lateral roots were painted. This solution was prepared by dissolving, in 1 liter of water, 10 g of the commercial product Nafusaku (20% of NAA) and then mixed with 500 g of kaolin or talc to form a past. This treatment was done just after the plucking of the seedlings and soon afterwards they were left under shade and planted in the following day.
Transport of the seedlings to the field
The seedlings were then carefully arranged in a cart, in separated layers, using green vegetative material (vegetative leftovers), aimed at to soften the impacts and avoiding further damages to the seedlings, especially to the swelled buds and the tip of the taproot, already in a regeneration process.
Preparing of planting holes
The planting holes for these seedlings were prepared the following way: the hole was dug at a dimension of 50 cm by 50 cm and 30 cm of depth, tapering after 15 cm to a conical shape of 15 cm in diameter thus, allowing for better sustainability for the budded-stumps and avoid the formation of air chambers, that influences the success index of take, as illustrated in the Figure 4.
Planting the seedlings in the field
The prepared seedlings were planted in the field during the period of March to April 2004, in single row with spacing of 2.5 m between plants, demarcating areas of approximately two hectares for pasture. The process of planting required that some soil be mixed with 70 g of triple phosphate and 10 liters of mature cattle manure for re-filling the hole while ensuring firm adjustment around the tip of the taproot (Figure 5). Further compacting of the soil mixture was required around the seedling with the aid of a small piece of wood, thus avoiding the presence of air in contact with the roots. Using vegetative material as mulch, a ground cover was positioned around the seedling.
The rubber tree is a plant of economical value, with properties that makes it ecologically friendly. For this reason, it plays an important part in numerous programs aimed at sustainable agriculture systems, due to its advantages of fast growth, possibility of using different types of seedlings, in addition to good rooting capacity, desirable height and architecture (both easily manageable), little competition with other species, besides ease in wide environmental adaptation. Besides being a perennial plant it has other benefits, such as, a low-density canopy, a regular annual leaf–fall, and together with the possibility in the successful use of seedlings (budded-stumps), transferred at an advanced age to the field provides stakes for live fences. Consequently, this serves to prevent environmental destruction of valuable forest, only for removal of wooden stakes, conventionally used for fencing of farm land.
The rubber tree has a high capacity for sequestrating atmospheric carbon and hence, could be now explored for this function. It can be perfectly incorporated in the Clean Development Mechanism of fixing carbon and liberate oxygen. There is a growing world consciousness aimed to lessen atmospheric carbon dioxide, motivating a promising market for carbon. These resources can be channeled to those areas that make a positive contribution in reduction of CO2 pollutant. Introducing rubber trees in pastures would optimize the process of carbon sequestration, to a larger capacity of absorption of CO2 (16.6 ton/hectare) when compared to pastures areas alone (14.3 ton/hectare) shown in recent studies (Soares and Fernandes, 2003).
Another positive factor is the fixation of man to rural areas. Rubber trees put a high demand on hand labor during the different phases of development of the crop and when providing valuable returns, when rubber is tapped. This guarantees more job opportunities, improvement in living standards of communities, through amassed incomes from agricultural enterprises, like cattle breeding, together with the added benefit of commercialization of the rubber. In Bahia its contribution for the labor generation surpass 18 times the livestock with a relationship of one laborer for each four hectares. And even when compared to the perennial cultures, it has the advantage of not presenting the seasonal character, providing also good shade for the cattle.
The authors express their acknowledgments to Mrs. Maria Helena Serôdio for the revising of this article and to Mr. Raimundo Marques da Silva for collaborating in the graphic composition.
MORAES, V.H. de F. 1992. Operações de pré-plantio do toco alto de seringueira. Manaus: EMBRAPA. CPAA, Circular Técnica nº 5. 40p.
PEREIRA, A. V. e PEREIRA, E. B. C. 1985. Mudas de seringueira. Manaus: EMBRAPA. CNPSD, Circular Técnica nº 7. 52p.
SOARES, C.A.B. and FERNANDES, T.J.G. 2003. Projeto de MDL com seringueiras no Mato Grosso e a questão da geração de empregos. In: I Simpósio Brasileiro de Carbono sobre Fixação de Carbono em Sistemas Florestais. Londrina, PR. CD-Rom
TRABALHADOR EM SERINGAIS. Serviço Nacional de Formação Profissional Rural/CEPLAC. CBR - Coleção Básica Rural, Brasília, 1981.
Raimundo Bonadie Marques