Erratum to: The impact of El Niño Southern Oscillation on seasonal drought in the southern Australian grainbelt

Abstract

The cropping simulation model APSIM (Agricultural Production Systems Simulator) was used to investigate the pattern of seasonal moisture stress during the growing season for four medium- to high-rainfall regions and four low-rainfall regions in the southern Australian grains belt over the period 1906–2007. Cluster analysis of the pattern of crop water stress experienced by each simulated crop was used to devise season types for the study sites. Average crop moisture stress for two periods up to grain filling, i.e. germination to 600°C days of thermal accumulation (~Zadoks 0–32) and from 600 to 1200 days of thermal accumulation (~Zadoks 32–71), was used to devise a classification of season type: low moisture stress early and late (L-L), low early and high late (L-H), high early and low late (H-L) and high early and late (H-H). Using regional rainfall we found that El Niño events are associated with double the risk of the season being in the lowest tercile from 33 to 67% and La Niña events increase the chance of being in the top tercile to 50%. Although there was a wide range of simulated yields in El Niño and La Niña years, for most sites the average yields were lower in El Niño years and higher in La Niña years. For most sites in the study 6 or 7 of the worst 10 years were El Niño, 3 Neutral and 1 or nil cases were La Niña events. This contrasts with a pattern assuming no El Niño Southern Oscillation (ENSO) influence of 2 El Niño, 6 Neutral and 2 La Niña events. Analysis of the relationship of season types identified by the cluster analysis to ENSO showed significant results for high-rainfall sites but not for low-rainfall sites. One of the reasons for this is that in low-rainfall sites, moisture stress occurs in most seasons. We conclude that there is good reason for farmers and advisers in South Australia to pay attention to a forecast of ENSO for the coming season as one part of their risk management strategy. We conclude on the need to think clearly about drought and aridity in these low-rainfall environments and comment on how this analysis further questions canopy management as a means of dealing with drought risk.