Abstract
Harvesting latex, a key activity in the production of natural rubber (NR), involves repeated tapping of the bark on the main trunk of the trees. Low frequency harvesting (LFH) systems are only economically feasible with the use of Ethephon (ET) which stimulates the tree to provide high yield per tap as a compensation for the yield loss due to lowering the tapping frequency. Ethephon concentration and its frequency of application may vary with the frequency of harvesting used. Latex samples were collected from genotypes; RRIC 100, RRIC 102, RRIC 121 and RRIC 130 harvested under S/2 d2, S/2 d3, S/2 d4 and S/2 d6 (i.e. tapping half of the spiral of tree once in two, three, four and six days, respectively) systems were processed into lace crepe and assessed for raw rubber properties viz. initial plasticity (Po), plasticity retention index (PRI), Mooney viscosity (VR), colour, nitrogen and ash content. No significant differences were observed among different LFH systems with respect to each raw rubber property tested. However, clonal differences in those raw rubber properties were prominent. Therefore, the study revealed that the low frequency harvesting systems tested with Ethephon stimulation do not have any effect on the quality of raw rubber produced.
Highlights
Introduction currently the natural rubber (NR) prices are attractive, the survival of the industry is being threatened by price volatility, spiraling cost of production and inadequate supply of skilled harvesters
Initial plasticity value of clone RRIC 121 was above the specifications for Lankaprene under all four harvesting systems
The highest Mooney viscosity value was observed in RRIC 130 whilst the lowest was in RRIC 100
Summary
Currently the natural rubber (NR) prices are attractive, the survival of the industry is being threatened by price volatility, spiraling cost of production and inadequate supply of skilled harvesters. Various technological advances made during recent past and the emergence of premium grades of crepe rubber i.e. Lankaprene, escalate the manufacturers’ interest on the quality and properties of raw rubber with an aim to maintain the smoothness of manufacturing process as well as the quality of the end product. For crepe rubber and premium grade Lankaprene, specifications for the major properties of dry raw rubber i.e. initial plasticity, plasticity retention index, Mooney viscosity, colour, nitrogen and ash (Table 1) have been stipulated (Seneviratne & Rathnayake, 2008). The pattern of latex production in the rubber tree varies with the genotype and with the harvesting system which include both stimulation and harvesting frequency.
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