The annual dry season in north Kedah, which can extend for two to three months, was interrupted in 2006 by three substantial rains at approximately monthly intervals. Measurements of CO₂ , latent heat and sensible heat fluxes above the canopy of five and a half year-old oil palm, supplemented by growth measurements, soil water and supporting meteorological data, indicated considerable mitigation by the rainfall of the effects of the dry season. Thus, reductions in CO₂ uptake, canopy conductance and evapotranspiration, and increases in sensible heat flux and accumulation of spear leaves, were less than expected.
The data suggest that even infrequent irrigation during a dry season may suffice to prevent a substantial build-up of stress in the palms under the edaphic conditions of the trial. Further observations to determine the long-term impacts on yield are, however, necessary.