A single post head-emergence frosts (PHEF) event has the potential to devastate individual wheat crops by damaging stems and killing whole heads. Wheat crops are most sensitive after head emergence and hence management of crop phenology to avoid PHEF is very important in regions where frost risk is high.
The opportunity costs due to direct yield losses and delayed sowing (indirect frost effect) were evaluated with careful consideration of extreme-temperature events, sowing dates and flowering times. To evaluate such opportunity costs, APSIM-Wheat (7.6) simulations were integrated with economic modelling. The APSIM-Wheat model adapted to account for frost (Zheng et al., J Exp Bot, in press) was used to simulate wheat crops sown at one day intervals within a fixed sowing window from 1st April to 30th June for selected 60 sites across the Australian wheatbelt.
Economic results highlighted a strong influence of sowing dates and cultivar maturity types on the direct cost of frost. For example, for mid-season flowering cultivar in eastern wheatbelt, the direct damage of early sowing can range from AU$ 60 to AU$ 500 per ha. When estimating costs for direct plus indirect frost impacts, loss can range from AU$ 70 to AU$ 680. Overall, regional direct plus indirect losses were substantial across the entire wheatbelt. For an agro-ecological zone like New South Wale Central, direct plus indirect lost were estimated at AU$m 480. Breeding for improved reproductive frost tolerance thus appears as a potential avenue to provide significant economic benefits to the Australia wheat industry.