Relationship between the Southern Oscillation Index and Australian sugarcane yields

This study examines the relationship between the Southern Oscillation Index and the sugarcane yield anomalies at 27 mills in north-eastern Australia (Queensland) for the period 1950-1989. The major results of this work indicate that the SO1 alone seems to have only a limited value as predictor of total sugarcane yields over large areas (i.e. the whole of Queensland). However, on a smaller scale, the SO1 appears to be a useful indicator of yields for the northern sugarcane districts. In these northern areas, the highest correlations with the SO1 are reached during the southern hemisphere spring and summer months 6 to 11 months prior to the harvest. They are negative and explain about 40% of the total variance. They also suggest that a positive SO1 during the spring and summer months tends to be followed by lower-than-normal yields at the following harvest and vice versa. This signal is rather robust and withstands rigorous significance testing. Moreover, it appears that the relationship between the SO1 and the sugarcane yields has been relatively strong and stable for the past 40 years, but weakened substantially during the 1930-1940 period.