Wheat yields unchanged despite rainfall decrease

CSIRO research indicates that — despite a rainfall decrease in Western Australia’s wheatbelt between 1900 and 2016 which has shifted wheat yield potential south-west by an average of 70 km — wheat yields have remained unchanged.

CSIRO Farming Systems Scientist Dr 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.

“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,” Dr Fletcher said.

The Western Australian wheatbelt covers about 60,000 km² and produces close to one-quarter of the nation’s crop, 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.

The impact of climate change on cropping is particularly pronounced in Western Australia as the state has undergone a significant shift in rainfall patterns.

With findings published in Climatic Change, the study analysed 117 years of daily climate data from 1900 to 2016 using the APSIM model developed by CSIRO and partners.

Climate data such as rainfall was combined with soil type to determine yield potential at numerous points across the WA wheat belt for each of the 117 years.

CSIRO Senior Experimental Scientist Dr 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,” Dr Chen said.

While the overall yield potential in Western Australia shifted (on average) 70 km to the south-west, this is being offset by 35 km due to increased CO₂, 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,” Dr 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.

Image courtesy of CSIRO.