WA farmers staying ahead of the curve, despite 100-year rainfall decline

By Andrew Fletcher, Chao ChenApril 8th, 2020

Despite a rainfall decrease in Western Australia’s wheatbelt between 1900 and 2016, which has shifted wheat yield potential southwest by an average of 70km, actual wheat yields have increased.
Shifting wheat yield potential

Wheat farmers are adapting to changing growing conditions.

New research published in Climatic Change, demonstrates the importance of research and development and the continued ability of farmers to innovate and adapt in order to keep ahead of the declining yield potential curve. 

The study analysed 117 years of daily climate data using the APSIM model developed by CSIRO and partners. Climate data, including rainfall, was combined with soil type to determine yield potential at numerous points across the WA wheat belt for each of the 117 years. Yield potential is the yield farmers could achieve given the climate and soil type and using current best practice and technologies.

Adapting to change

The research showed that up until 2000, yields had been increasing but after that, they did not increase, and year-to-year variation increased. This is consistent with a 2017 CSIRO study showing national wheat yields had stalled since 1990, when they had previously been increasing. 

To adapt to the reduced rainfall, Western Australia’s farmers are employing a range of tactics, recognising that they can’t keep doing what they’ve always done. Many are now sowing their crops earlier in the season and also dry sowing rather than waiting for autumn rain. 

Without this continuous improvement in crop genetics and agronomic practice, Western Australia could well see a decrease in wheat yield associated with a changing climate. 

The impacts of climate change on cropping are especially pronounced in Western Australia as the state has undergone a significant shift in rainfall patterns. This change is due to the southward movement of weather systems attributable to climate change. 

The Western Australian wheatbelt covers about 60,000 square kilometres and produces close to one quarter of the nation’s crop, valued at $1.4 billion.

Yield potential in the Western Australian wheatbelt has shifted on average 70km southwest from 1900 to 2016.

Shifting yields

While the overall yield potential in Western Australia shifted on average 70km to the Southwest, this is being offset by 35km due to increased CO2, which improves plant growth. However, overall the benefits of increased CO2 are far outweighed by a reduction in rainfall, the major limiting factor to crop growth. 

In the future, the gap between yield potential and actual yields will likely close due to climate change as potential yields decrease. 

Similar shifts in yield potential, as seen in Western Australia, are likely to have occurred in other parts of Australia and in other countries. However, to-date, the analysis that was done for this study has not been carried out elsewhere. 

The research was supported by investment from the Grains Research and Development Corporation (GRDC). 

1 comments

  1. Is this “gain” in yield at the expense of our soils ability to support these yields without constantly increasing expensive inputs. Are we slowly/maybe not so slowly, destroying soil biodiversity and structure. How long wil our impoverished Western Australian soils support this. These are the questions we should be asking our scientists not just the blind quest for increased yields, lets start looking at regenerative agricultural techniques and making our agricultural production more sustainable. We should be reversing the damage done over the last century of farming practice.

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