Abstract
<em>Hevea brasiliensis</em> (Muell Arg.) undergoes annual leaf shedding commonly known as wintering. The wintering period in the traditional rubber growing areas in the Wet Zone of Sri Lanka is from December to February followed by flowering and flushing in March. Tapping rest during wintering is recommended in certain countries while in some other countries year round tapping is practiced. In Sri Lanka, until early1970s winter resting was practiced, but this is not being practiced at present. Incidence of tapping panel dryness appears to be high with currently recommended clones and hence the objective of the present study was to investigate on the effect of winter resting on the annual yield and tapping panel dryness in rubber clones. Experimental trials were conducted for two consecutive years (2018 and 2019) with three clones viz., RRIC 100, RRIC 121 and RRISL 203 at the Substation of RRISL at Kuruwita in Ratnapura district. Treatments tested were continued tapping with no winter rest (T1), resting during the wintering period (T2) and once in six days tapping during the wintering period (T3). Trees were tapped at S/2d3(once in three days) intensity. Data were collected on latex volume, bark consumption and TPD incidences. Results for two years showed higher g/t/t/ in all three clones when rested during the wintering period in both years as compared to those with no winter rest. Significantly higher annual total crop (kg) was recorded for T1 when compared to T2 in all three clones for both years. Though total number of partially and totally dry trees of winter rested trees of clones RRIC 100 and RRIC 121 were low, the differences were not significant. In terms of profits obtained as indicated by economic analysis, resting the trees during wintering resulted in the highest profits, followed by d6 tapping during the same period. Winter rest should be tested for a longer duration (4-5 years) for all the clones recommended at present that are vulnerable to tapping panel dryness.
Highlights
Wintering is a term that is used to describe the annual shedding of senescent leaves which renders the tree partially or fully leafless for a period of time
Unlike in trees in temperate countries where defoliation occurs during the winter period of the year, in Effect of winter resting on yield rubber which grows in tropical countries, wintering takes place during the drier months of the year
Monthly total crop of the ten trees for the two years and for three treatments, for continuous tapping (T1), winter rested (T2) and d6 tapping during the wintering period (T3) for the three clones are given in Tables 1a, 1b and 1c
Summary
Wintering is a term that is used to describe the annual shedding of senescent leaves which renders the tree partially or fully leafless for a period of time. As reported by Liyanage (1976), wintering has been induced by drier weather and much influenced by rainfall occurring during the period as observed in clone PB 86, in an experiment conducted in almost all rubber growing areas in Sri Lanka. It is hypothesized that the tapping frequency of d2 or d3 with ethrel may be too harsh for the high yielding clones and continuous tapping without a rest during wintering and flowering period could be one of the major reasons for trees to become stressed and occurrence of high TPD in rubber clones. The current study, was aimed at investigating the effect of tapping rest during the wintering and flowering period on latex yield and tapping panel dryness incidence in three selected rubber clones
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