Harvesting rubber latex is rather labour intensive since trees are traditionally tapped half spiral, once in two days (S/2 d2) resulting in unnecessary waste of tree bark. High cost of production, shortage of harvesters and reduced economic lifespan are the key issues in rubber plantations related to harvesting. Low intensity harvesting (LIH) systems (i.e. either reduction in harvesting frequency and/or tapping cut length) of rubber appear to be a practical solution to these issues by bringing down the labour requirement and the cost of production. Of these, only the reduction in harvesting frequency has been tried in Sri Lanka. Hence, the present study was aimed to develop new LIH systems with shorter tapping cuts. This study comprised two stage stimulant (Ethephon) based field trials to evaluate a wide range of LIH systems. The overall yield given by traditional S/2 d2 was used as the standard in evaluation. Stimulation protocols of different harvesting systems were adjusted from time to time to achieve this standard. In addition, growth and physiological parameters of latex and the financial viability of the principal system were also assessed. Among the LIH systems tested, S/4 d3 (tapping quarter spiral once in three days) was successful in providing benefits, such as increase in both overall profits and harvesters' income and reduction in harvesting cost and overall cost of production. The overall bark consumption was also greatly reduced. Above all, it allows tapping the virgin bark of base panels for over 24 years. Popularization of this approach is proposed after large scale commercial testing.

Escalating cost of production (COP) and inadequate supply of skilled harvesters are among the major issues that natural rubber industry face today. Low frequency harvesting (LFH) systems of which trees are tapped in a lesser frequency than once in two days, are considered to be one of the solutions to overcome these issues. With the focus given to expand rubber in drier climates, the present study was aimed to investigate on the yield response of LFH systems, viz. harvesting trees once in three (d3), four (d4) and six (d6) days in the intermediate zone (IZ) with the stimulation protocols developed for the wet zone (WZ). With the decrease in harvesting frequency in IZ, yield per tree per tapping (GTT) increased, however yield per tree per year (YPT) decreased. No such declines were observed in WZ. Stimulation had no negative impact on percentage dry rubber content in latex (%DRC) or incidence of Tapping Panel Dryness. Whilst only the S/2 d3 system is acceptable for IZ in the present form, stimulation protocols are to be revised in other LFH systems. Bark consumption was reduced significantly by LFH resulting in several long-term beneficial effects. Effect of stimulation on latex physiology is also discussed.

Low frequency harvesting (LFH) systems of rubber (Hevea brasiliensis) result in reduction in labour use and cost. However, yield stimulants (viz. Ethephon) are to be applied to enhance the yield in each harvest as a compromise for the yield reduction due to less number of harvesting days. A system of harvesting the tree once in four days (S/2 d4) has recently been introduced and a weekly harvesting system (S/2 d7) is presently under investigation. In S/2 d4 and S/2 d7, the required doze of Ethephon has exactly not known and that would vary with the climatic condition. Therefore, the present study was aimed to identify the suitable concentrations of Ethephon required for S/2 d4 and S/2 d7 systems under two climatic regions, wet and intermediate zones of Sri Lanka. Ethephon was applied in four concentrations (i.e. 2%, 3%, 4% and 5%) and yield performance in each system was evaluated against that of the traditional harvesting systems of S/2 d2 (tapping the tree once in two days). In the Intermediate zone, S/2 d4 and S/2 d7 systems showed a yield increase of 7 and 14 grams per harvest per 1% increase in Ethephon concentration, respectively. In the Wet zone, respective increases were recorded as 4 and 7 grams. The S/2 d4 system required ca. 3.7 % and 3.2 % concentrations of Ethephon in the Intermediate and Wet zones, respectively, to achieve the yields given by S/2 d2 system. In S/2 d7, 5% Ethephon was sufficient for both zones. Ethephon concentrations tested had no adverse effects on tree health. Needs for commercial scale studies with financial analyses are discussed.

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 (V R), 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.

The objective of this study was to evaluate the girth and yield performance of new Hevea genotypes obtained from the 1998 hand pollination (HP) program. Sixty-five new genotypes were assessed along with the control clones viz. RRIC 121, RRIC 130 and RRISL 205. Dry rubber yield for six years, annual girth at the 14 th year and girth increment, percentage of tappable trees, survival trees and tapping panel dryness affected trees and latex properties of selected genotypes were evaluated. Considering the results, 63% of the genotypes were recorded as significantly higher or similar average yield compared to control clones. The genotypes, 98-80 and 98-219 were the top-rankers with average yields of 53.7 g and 52.0 g per tree per tapping, respectively. Moreover, the progeny generated from 1998 hand pollination consisted of good yielders similar to the yield of the clone RRIC 121 and could be considered as potential candidates for future clonal selection programmes to develop elite clones. Eighty-two percent of the genotypes showed significantly higher or similar mean girth compared to controls. Genotypes, were ranked at number one and two, which have obtained respective girth values of 80.6 cm and 76.5 cm. Eighteen percent of genotypes recorded more than 70 cm of mean girth, which was an indicator of the development of vigorous timber clones in the future. Moreover, these genotypes possess high yield potential. Almost all the genotypes had significantly high girth increment during the immature phase than the post tapping phase. Genotypes 98-80 and 98-219 had performed well based on the dry rubber content (DRC), sucrose and inorganic phosphorus values. In conclusion, the 1998 HP programmes has generated a valuable pool of genotypes that have paved the path to producing outstanding Hevea clones.