Farm Table says:
What is the problem?
Understanding why there is such variability in wheat yield in any given year.
Climate variability explains about 43% of the year to year wheat yield variability in the Australian, with the variation in the sowing date resulting in a variation of 30 – 68%.
What did the research involve?
A study in WA has also indicated that environment × management interaction (i.e. seasons, locations, seed rate, sowing time, and N fertilizer rates) also accounts for 70% of yield variation.
This study at Wagga Wagga (NSW) involved field experiments on wheat type × irrigation with differing sowing dates: late sowing in 2013 and early sowing in 2014.The experimental area had 24 plots each year with each experiment having three replications. Factors were variety and irrigation. There were two soil water regimes: irrigated and rainfed. Soil moisture content was measured using neutron soil moisture probes. A target wheat population of 120 plant/m2. The 2013 experiment was sown on 24 June and the 2014 experiment sown on 30 April.
Nitrogen fertilizer was applied at sowing at a rate of 100 kg ha−1of urea.
In 2014, two months after sowing, additional nitrogen fertilizer was applied at a rate of 50 kg ha
Irrigation was applied during the flowering and grain filling stages in both years. The number of irrigations was ten and nine in 2013 and 2014.
What were the key findings?
A combination of irrigation, choice of mid-late flowering varieties and early sowing can result in an increased grain yield. A mid-late flowering wheat variety when sown early and irrigated can result in a relatively higher yield compared to early sown short-season variety. Irrigation applied in spring significantly improves the yield of a mid-late flowering wheat variety compared to that of an early flowering variety.
Availability of varieties of different-times-to-flowering allows more flexibility in the time of sowing which suits the seasonal condition and maximizes yield and profit. Long duration varieties are less risky when the seasonal conditions necessitate sowing outside of the optimum sowing period. Under severely water-stressed spring period, however, long-season varieties can yield less than short-season varieties. The difference between the times to flowering (and also potential yields) of an early flowering and mid-late flowering varieties decrease as the sowing date is delayed.
Therefore, in late-break years of delayed sowing, factors such as disease resistance and grain quality become more important than grain yield in choosing a variety.