Journal of Oil Palm Research Vol. 4 No. 1 1992 June, p. 32-43
THE EFFECTS OF SEASON RAINFALL AND CYCLE OF OIL PALM YIELD IN MALAYSIA
Received: 6 August 1991
A statistical model incorporating simultaneously the long-term trend, season, rainfall and lagged yield, appears to give a reasonable explanation of the variations in average oil palm yield as expressed by crude palm oil (CPO) production in Peninsular and in East Malaysia.
Variations in CPO production are noted of 53%-57% due to season, being independent of long-term trend, of 12%-24% due to rainfall and of l0%-20% due to tagged yield effects. The seasonality in oil palm yield, being highly significant at the national level, could be quite independent of rainfall though rainfall has apparently interacted with and modified the seasonality pattern to some extent.
Substantial positive correlations of yield with rainfall at lags of 20-24 and 10-11 months (before harvest) clearly relate to the crucial periods of sex differentiation and inflorescence abortion respectively, the effects of which appear to be quite different as between Peninsular and East Malaysia.
The number of negative correlations between palm yield and rainfall may be of interest. A negative correlation at a lag of six months is indicative of some adverse effects of excessive rainfall on anthesis and pollination; those at lags of 30-36 months are probably related to inflorescence initiation. Negative effects of rainfall are also observed at lags of 0-2 months, indicative of the period of oil synthesis. Some significant negative correlations, particularly at a lag of 13 months, and a possible positive correlation at 17 months, have yet to be explained biologically.
A marked positive yield effect at a tag of 16 months and a moderate correlation at 21 months seem to suggest major yield cycles with such periods.
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* Palm Oil Research Institute of Malaysia,
P O Box 10620,
50720 Kuala Lumpur