This paper is a preliminary attempt to understand the decadal trends in the yield of selected Hevea clones in the traditional regions based on time series data on commercial yield of three popular clones viz., GT 1, RRIM 600 and RRII 105, from the organized large estates. The trends in average yield (kg ha-1) of the three clones for the first 10 years of tapping during different decades was assessed and inter- decadal growth rates in yield were estimated. Trends in other yield related variables viz., planting density and tapping systems followed were also considered. The analysis revealed a steady decline in the ten year average yield of clones planted during different decades, except an aberration in the case of RRIM 600 during the 1970s. Although the decadal trends in yield fatigue has been reversed to certain extent by the higher yield of high yielding (HY) clones like RRII 105, the trends in yield of the same underline the inherent limitations. The observed changes in planting density and tapping systems are not expected to be yield depressing. Hence, the observed yield fatigue are construed to be the cumulative effect of depleting soil organic content and fertility as well as climate change.
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