Effect of variable crop duration on grain yield of irrigated spring-wheat when flowering is synchronised

Short duration spring wheat cultivars are currently preferred for irrigated wheat production in subtropical Australia due to their high levels of lodging resistance. A study was conducted to determine whether recently developed lodging-resistant long duration cultivars could achieve increased grain yield compared to short duration cultivars in irrigated sub-tropical environments. A key aspect of the study methodology required the use of different sowing dates for each maturity group to ensure anthesis was synchronised and thus occurred during the same climatic conditions. Growth of representative cultivars in each experiment was simulated using the APSIM model to characterise each environment for the presence of water or nitrogen stress. Results of the study indicated that the long duration cultivars had an increased grain yield of 0.67 t ha−1 (9.6%) on average across the 14 agro-climatic environments compared to the short duration cultivars. The response varied between agro-climatic environments, with long duration cultivars significantly higher yielding in 70% (or ten) of the environments, no significant difference observed in three environments, and a significantly lower yield associated with long duration cultivars in one environment. The yield advantage of the long duration cultivars was greater in environments where moderate water stress was experienced, with yield differences of up to 1.5 t ha−1 observed in the most water-stressed environments. The yield advantage was less apparent in environments where low levels of water stress were experienced, and in two environments where lodging was more severe among the long duration cultivars. The relatively small difference in duration between the long and short duration cultivars in this study may not have fully exploited the potential benefits of longer duration cultivars. The results suggest that genetic improvement programs should continue to develop longer season germplasm that conveys an adaptive advantage to irrigated sub-tropical environments such as Australia, India and Mexico that experience short-term water deficits, and in which deficit irrigation is often the most profitable strategy for farmers. Additional research is necessary to determine whether ultra-long duration cultivars could further raise yield potential in sub-tropical environments if lodging could be avoided, through either genetic improvement or improved access to plant growth regulators.