THE DRIER and hotter conditions experienced in Western Australia over this century have not led to a drop in yield according to recent CSIRO research.
Andrew Fletcher, farming systems scientist at CSIRO, found that the area with an average yield potential of 3.2 tonnes a hectare, around the state average in terms of hypothetical potential, had moved an average 70 kilometres to the south and west over the past century.
Yield potential is the best possible yield based on available sunlight and water and best practice farming practices.
Dr Fletcher said in spite of best possible potential dropping actual yields had not fallen by the same amount due to advances in areas such as agronomy and variety selection.
"We are achieving better percentages of the yield potential due to these advances, which is helping keep up ahead of the curve."
Dr Fletcher said although it looked like yields had stagnated over the past 20 years, the mere act of maintaining those yields had been quite a feat.
"Given the warming and drying pattern we have seen, especially since 2000, maintaining those yields is a phenomenal achievement," he said.
He said improvements to water use efficiency, driven by innovations such as the push to no-till systems from the 1980s to the early 2000s had made it possible to get better value from each drop of rain.
And moving forward he was confident there would be more advances.
"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.
"However, things are changing and the push towards things like earlier and dry sowing are helping farmers to maintain their yields in the face of a drying climate.
"They will be faced with new challenges, such as increasing herbicide resistance but a combination of breeding and agronomic advances will help mitigate yield decline."
High on the wishlist according to Dr Fletcher was the development of a profitable pulse crop suitable to the acid soils which dominate the WA wheatbelt.
"That's been a Holy Grail for some time it would allow more flexibility in the rotations," he said.
The Western Australian wheatbelt covers about 60,000 square kilometres and usually produces close to one quarter of the nation's crop, valued at $1.4 billion.
The data used by in the study, co-founded by the Grains Research and Development Corporation (GRDC) was from 117 years of daily climate data from 1900 to 2016 using the APSIM model of yield prediction to generate figures.
Dr Fletcher said the findings could be similar in other areas, especially mid-latitude regions with Mediterranean climates, such as SA, Victoria and southern NSW, where rainfall deficits under climate change have been most pronounced, however he said he did not have the data to prove it.
The big drop in rainfall in the southern and western cropping zones is due to the southward movement of weather systems.
Typically the summer rain that provides much of the moisture in northern NSW and Queensland is not modelled to decline to anywhere near the extent in-season rainfall is in the south.
Senior experimental scientist at CSIRO 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.