Frost Trends and their Estimated Impact on Yield in the Australian Wheatbelt

Spring radiant frosts occurring when wheat is in reproductive developmental stages can result in catastrophic yield lost for producers. Yield potential is also reduced in areas where producers are obliged to sow late to avoid the peak frost risk period. To better understand the spatial and temporal variability of frost events, 0.05° gridded weather datasets were used to calculate frost occurrence and frost impact on wheat production across the Australian wheat belt. Over the last 57 years, no significant trends in frost occurrence were observed in most of the Australian wheat belt. However, more frost events and later last frost days occurred in major parts of production areas while the opposite was rarely observed. Yield impact was simulated at 60 key locations using the Agricultural Production Simulation Model (APSIM) with a newly developed frost module. A significant increase in frost impact on yield was estimated in the higher-elevation areas of south eastern Australia in the states of Victoria and New South Wales. Across Australia, we found that yields could be improved by up to 20% on average if frost tolerant lines were available. The yield increases resulted from (1) reduced frost damage and (2) the ability to use earlier sowing dates. Simulations suggest that a small reduction in the threshold temperatures, equivalent to frost tolerance of 1 °C lower than current cultivars would predicted a large effect on the occurrence of frost damage in the west of Australia. In the east, frost tolerance to lower temperatures (∼ −4 °C) would be required to maximise the yield advantage. Thus despite global warming, breeding for improved reproductive frost tolerance remains a high priority for the Australian wheat industry.