Mixing it up - wheat cultivar mixtures can increase yield and buffer the risk of flowering too early or too late

Mixtures of wheat cultivars of different duration can potentially balance the yield-reducing risks of frost, heat and terminal drought. Cultivar mixtures with contrasting duration were tested across three experiments in Western Australia. Experiment 1 consisted of three sowing dates (early, mid and late), experiment 2 consisted one sowing date and experiment 3 consisted of two sowing dates (early and late). The three experiments and the multiple sowing dates created differences in the exposure to frost, heat and terminal drought risk. Seven treatments were established in each environment, consisting of three commercially-available cultivars (long, mid and short-duration); together with each of the two- and three-cultivar mixtures of these cultivars. In experiment 1 yields of the single cultivars showed the expected pattern with the long duration cultivar having the highest yield when sown early and the short duration cultivar having the higher yield when sown late. There were few differences in yield in experiments 2 and 3. Only a single treatment, a mixture of the long and mid-duration cultivars, was either the highest yielding or not significantly different from the highest yielding across all environments. In experiment 1 there was evidence of over-yielding with the mean of all the mixtures being 6.4% greater (P = 0.043) than the mean of the individual cultivars across the three sowing dates. This research has demonstrated that wheat cultivar mixtures can stabilise the combined risks of frost, heat and drought stress in frost and heat-prone dryland environments, providing growers with a strategy to manage these uncertain risks.