Counter to the idea that a warming climate might decrease frost damage, new research suggests that rising temperatures could actually increase frost-induced yield losses.
Highlighting this paradox is the first national assessment of frost trends and their yield impact across the Australian wheatbelt from 1957 to 2013.
The study stems from research at the University of Queensland (UQ), the Queensland Department of Agriculture and Fisheries, the Queensland Alliance for Agriculture and Food Innovation and CSIRO.
Dr Jack Christopher, who is leading the GRDC co-funded project at UQ, explains that higher temperatures accelerate plant development, which means wheat can reach sensitive post-heading growth stages earlier, when frost risk is high.
For growers, this finding suggests that sowing wheat earlier in warmer conditions with the aim of lifting yield potential could have the opposite effect and lead to reduced yields if the crop clashes with a frost event.
Judging this is the big challenge and it is different across grain-growing regions.
Dr Christopher says that modelling of the timing of crop heading clearly indicates that varying climatic conditions in different growing regions will require different strategies.
For example, the research indicated that yield losses caused by both frost itself (direct damage) and delayed sowing to help avoid frost risk (indirect losses) varied notably from region to region. This is because the last frost comes earlier in some areas and later in others.
The research further showed that nationally, direct frost damage caused average crop losses of between 10 and 11 per cent. But the combination of direct frost damage and indirect losses due to delayed sowing caused average yield reductions of 20 per cent, 21 per cent and 18 per cent respectively in early, mid and late-flowering wheat varieties.
Sowing time was found to be the most important factor in maximising wheat yields, particularly in the northern grains region where delayed sowing was the biggest contributor to yield losses.
In the northern grains region, the combination of frost damage and delayed sowing to reduce frost risk led to 34 per cent, 38 per cent and 23 per cent yield losses respectively in early, mid and late-flowering varieties.
Dr Christopher says growers are urged to continue to sow varieties with different flowering dates within the sowing windows recommended in National Variety Trials regional sowing guides.
This research is part of a multi-pronged approach to managing frost in grains operations across the country through the GRDC National Frost Initiative.
Dr Jack Christopher,
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