An increasing incidence of atmospheric pollution in the Southeast Asian region leading to substantial reductions in solar radiation has promoted concern over the possible long term effects on oil palm yields. Previous models of oil palm growth and production have emphasized the importance for yield of adequate radiation but effects of reduced radiation on yield are not immediately apparent due to the long time required for bunch morphogenesis, the complexity of the process and the presence of assimilate stores which serve to buffer the palm against periods of adverse conditions.

Because climatic factors other than radiation influence the physiological processes on which productivity is dependent, models were developed to take into account the other main factors, namely, temperature , atmospheric vapour pressure deficit (VPD) and soil water availability . Temperature had only a small effect because variations in mean temperature were small. Soil water availability had a larger influence but VPD was the most important factor influencing yields. A lower VPD, lower temperature and improved soil water supply associated with reduced radiation tended to offset yield reductions due to lower light intensity. Under certain conditions, predicted yields were higher under low or moderate than under high radiation. High radiation was associated with high evapotranspiration (ET) rates and lower rainfall, leading to increasing likelihood of soil water deficits and drought-induced yield reductions.

The results of the modeling exercise are related to palm performance in other regions with contrasting radiation receipts.