Andrew Fletcher1, Gary Ogden2
1 CSIRO Agriculture & Food, Centre for Environment and Life Sciences, PMB 5, Wembley WA 6913, firstname.lastname@example.org
2 CSIRO Land & Water, Centre for Environment and Life Sciences, PMB 5, Wembley WA 6913
Although there is a site specific optimum flowering window for wheat crops that balances the risks of frost, heat, terminal drought, frost and heat events are unpredictable leaving farmers uncertain about which wheat phenology to sow. Wheat variety mixtures that contain genotypes with different phenologies can mitigate this risk. Three varieties; Yitpi (long-season), Mace (mid-season) and Tammarin Rock (short-season); and each of the two and three variety mixtures; were sown on 8 May (early-sowing), 23 May (mid-sowing) and 2 Jun (late-sowing) 2015 at Brookton (WA) to expose the crops to varying degrees of frost around flowering and heat stress during grain filling. There were 14 frost events between 25 Aug and 11 Oct; and 15 heat events between 24 Sep and 31 Oct that coincided with flowering and grain filling, respectively. As expected, the long-, mid- and short-season varieties had the highest yields in the first-, mid- and late-sowing, respectively. A quadratic relationship between peak flowering date and yield showed that the optimum flowering window was from 7 to 25 Sep. For a given sowing date, the mixtures had yields that were intermediate between their component varieties, because they had a wider flowering spread than the single varieties. This meant that across the three sowing dates the mixtures had less yield variability than the single varieties. This research has demonstrated that wheat variety mixtures can stabilise the variable risks of frost, heat and drought stress in a frost prone environment.