El Nino-southern oscillation influences on rice production in Sri Lanka

Despite advances in the capacity to predict the evolution of the El Nino-southern oscillation (ENSO) phenomenon and advances in understanding the influence of ENSO on rainfall in tropical regions such as Sri Lanka, there has been limited use of climate predictions for agricultural decision-making. Climatic fluctuations have a profound influence on the cultivation of crops such as rice, which is the staple food in Sri Lanka. Here, the relationship between the sea-surface temperature-based ENSO index of NINO3.4, rainfall and the departure of Sri Lankan rice production from long-term trends, is analysed for the 'Alaha' (October to March) and 'hala' (April to September) cultivation seasons between 1952 and 1997. During the El Nino phase, the Maha rice production frequently increased (10 out of 15 seasons) and the Yala production frequently decreased ( 10 out of 14 seasons). Conversely, during the La Nina phase, the Maha production decreased (seven out of ten seasons) and Yala production increased (six out of eight seasons). Floods, state interventions, civil disturbances, fertilizer price hikes and extreme anomalies in the previous season were noted in the majority of seasons in which these ENSO-production linkages were violated. The correlation of the Maha rice production anomaly with the average NINO3.4 from October to December was significant at the 5% level and that with the aagregate October to December rainfall was significant at the 1% level, KIM rice production showed a significant relationship with concurrent NINO3.4 and a strong correlation (r = 0.60) with the previous season's rainfall. Yala cultivation is water constrained, and carryover storage from the previous season is often used to determine the extent of planting. The relationships between ENSO and seasonal rice production and the relationship between Yala rice production and previous Maha rainfall could be used for agricultural management and policy formulation. Copyright (C) 2002 Royal Meteorological Society.