The relationship between ENSO and rainfall and yield in the South African sugar industry

Information on the effects of El Nino on local climate and sugarcane production will assist planning and management. The objective of this study was to investigate the relationship between the southern oscillation index (SOI) and rainfall and sugarcane yields in South Africa. Probabilities of low rainfall more than doubled during summers with a consistently negative SOI phase during November. February rainfall was worst affected. Factors other than climate confounded the historical relationship between El Nino and sugarcane yields. Simulation studies to exclude non-climatic factors indicated that cane yields are reduced by significant margins following seven out of nine El Nino events. Results show that the phase of the SOI during spring is a reasonably reliable indicator of low rainfall during the subsequent midsummer and of low yields during the subsequent milling season.