Sunday 29th Mar, 2020

Western Australia wheat yields unchanged despite rainfall drop

Wheat yields in Western Australia’s wheatbelt have remained unchanged, even with more than 100 years of rainfall decrease, according to new research from the CSIRO.
Pictured: Chao Chen (L) Andrew Fletcher (R)

Wheat yields in Western Australia’s wheatbelt have remained unchanged, even with more than 100 years of rainfall decrease, according to new research from the CSIRO.

The study, published in Climatic Change, involved scientists analysing 117 years of daily climate data from 1900 to 2016 using the APSIM model developed by the CSIRO.

Researchers combines the climate data, including rainfall, with soil type to determine yield potential at a number of points across the wheatbelt.

Yield potential is the yield farmers could achieve given the climate and soil type using current technologies and best practice.

CSIRO Farming Systems Scientist Andrew Fletcher said the research highlighted the importance of research and development and the continued ability of farmers to innovate and adapt in order to keep farmers ahead of the curve.

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“Given the changing climate, it seems likely there will be a decrease in wheat yield in Western Australia without continuous improvement in crop genetics and agronomic practice,” Fletcher said.

Western Australia’s wheatbelt produces almost one quarter of Australia’s crop across around 60,000 square kilometres, valued at $1.4 billion.

Kit Leake, a fourth-generation wheat farmer from Kellerberrin, said increasingly they were sowing their crops earlier in the season and also dry sowing rather than waiting for autumn rain.

“It’s becoming more and more obvious that the climate is different now and we can’t keep on doing what we’ve always done,” Leake said.

According to the CSIRO, the impacts of climate change on cropping are especially pronounced in Western Australia as the state has undergone a significant shift in rainfall patterns.

The CSIRO said change is due to southward movement of weather systems attributable to climate change.

Fletcher said it was very possible that similar shifts in yield potential may have occurred in other parts of Australia and in other countries but to date, this kind of analysis had only been done for Western Australia.

CSIRO Senior Experimental Scientist Chao Chen said the research was consistent with a 2017 CSIRO study showing national wheat yields had stalled since 1990, when they had previously been growing.

“Up until 2000, yields had been increasing but after that, they did not increase and year-to-year variation increased,” Chen said.

The research found the overall yield potential in WA had shifted on average 70 kilometres to the Southwest, but this is being offset by 35 kilometres due to increased carbon dioxide, which improves plant growth.

“Overall, the benefits of increased CO2 are far outweighed by a reduction in rainfall, the major limiting factor to crop growth,” Chen said.

The researchers predict that in the future the gap between yield potential and actual yields will close due to climate change as potential yields decrease.