SEASON RAINFALL AND CROP VARIABILITY IN THE MACKAY REGION

AVERAGE CROP YIELD in the Mackay region in recent seasons (2008–2010) was 73 t/ha. This can be compared to the period from 1994 to 1998 when average crop production was 99 t/ha. This difference in crop production is of great concern to all sectors of the industry. This paper reports on an investigation into the effect of seasonal weather variability on the crop in the Mackay region. Seasonal conditions are one possible cause of the difference between the two periods. Total rainfall, effective rainfall, indicators of rainfall distribution, waterlogging, thermal time and solar radiation were used to define seasonal conditions. Analysis showed a significant correlation between seasonal weather parameters and crop variability in the Mackay region over the last two decades. Crop simulation over the period also suggested weather conditions were more conducive to crop growth in the mid 1990s than recently. Correlations between crop yield and rainfall variability for 20 year rolling periods commencing in 1951 were used in an attempt to determine the effect of rainfall variability on the Mackay crop over the longer term (1950–2010). The analysis suggested that the correlation between crop yield and rainfall variability had strengthened over time. This could imply that as management practices and varieties have improved, seasonal weather conditions becomes a more important driver of crop production in the region. However, industry expansion onto poorer soils and the condition of the soil after long term monoculture may also have affected the result. Overall, the investigation suggests that adaptation to seasonal weather variability is an important factor in industry sustainability. Management practices that allow flexibility in this regard, particularly irrigation, drainage, farming systems, timing of operations and suitable varieties need further investigation.